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TECHNICAL REPORT
Monitoring and evaluating changes
in cannabis policies: insights from
the Americas
January 2020
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Legal notice
This publication of the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) is
protected by copyright. The EMCDDA accepts no responsibility or liability for any consequences
arising from the use of the data contained in this document. The contents of this publication do
not necessarily reflect the official opinions of the EMCDDA’s partners, any EU Member State or any
agency orinstitution of the European Union.
PDF
ISBN 978-92-9497-461-7
doi:10.2810/151487
TD-02-20-009-EN-N
Luxembourg: Publications Office of the European Union, 2020
© European Monitoring Centre for Drugs and Drug Addiction, 2020
Reproduction is authorised provided the source is acknowledged.
Recommended citation: European Monitoring Centre for Drugs and Drug Addiction (2020),
Monitoring
and evaluating changes in cannabis policies: insights from the Americas,
Technical report, Publications
Office of the European Union, Luxembourg.
About this report
This report provides an overview of the changes in cannabis policies in the Americas
and the evidence emerging from evaluations of their impact. Highlighting the
challenges in monitoring and evaluating regulatory changes in the drugs field, it will
be of particular interest to those involved in planning or evaluating any changes to
cannabis regulation.
About the EMCDDA
The European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) is the
central source and confirmed authority on drug-related issues in Europe. For over
20 years, it has been collecting, analysing and disseminating scientifically sound
information on drugs and drug addiction and their consequences, providing its
audiences with an evidence-based picture of the drug phenomenon at
European level.
The EMCDDA’s publications are a prime source of information for a wide range of
audiences including: policymakers and their advisors; professionals and researchers
working in the drugs field; and, more broadly, the media and general public. Based in
Lisbon, the EMCDDA is one of the decentralised agencies of the European Union.
Praça Europa 1, Cais do Sodré, 1249-289 Lisbon, Portugal
Tel. +351 211210200
[email protected] www.emcdda.europa.eu
twitter.com/emcdda facebook.com/emcdda
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TECHNICAL REPORT
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
Contents
Acknowledgements ............................................................................................................................. 3
 
Executive summary ............................................................................................................................. 4
 
Foreword.............................................................................................................................................. 6
 
1. Introduction ...................................................................................................................................... 7
 
2.
3.
Background to cannabis policy developments in the Americas ...................................................... 9
 
A description and typology of different policy approaches ............................................................ 13
 
3.1
 
US approaches...................................................................................................................... 14
 
3.2
 
Uruguay ................................................................................................................................. 15
 
3.3
 
Canada .................................................................................................................................. 15
 
4. An assessment of early evidence of the impact of policy changes in the United States ............... 16
 
4.1
 
Literature review selection criteria......................................................................................... 17
 
4.2
 
Prevalence of use ................................................................................................................. 17
 
4.3
 
Consumption patterns ........................................................................................................... 23
 
4.4
 
Product differentiation and price ........................................................................................... 24
 
4.5
 
Treatment admissions ........................................................................................................... 26
 
4.6
 
Adverse medical events ........................................................................................................ 26
 
4.7
 
Impaired driving ..................................................................................................................... 28
 
4.8
 
Consumption of other substances......................................................................................... 30
 
4.9
 
Criminal justice and public nuisance outcomes .................................................................... 30
 
4.10
 
Tax revenues......................................................................................................................... 32
 
4.11
 
Public opinion ........................................................................................................................ 33
 
5. Issues to consider when establishing a comprehensive monitoring and evaluation framework for
changes to cannabis regulations .......................................................................................................... 34
 
5.1
 
Potential objectives of cannabis policy change and metrics of evaluation ........................... 34
 
5.2
 
Establishing the data infrastructure ....................................................................................... 40
 
5.3
 
Thinking seriously about outcome evaluations ..................................................................... 42
 
6. Concluding thoughts ...................................................................................................................... 45
 
References ............................................................................................................................................ 46
 
Appendix A: Identification and commentary on ongoing/planned studies of legalisation ..................... 52
 
US studies ......................................................................................................................................... 52
 
Uruguay ............................................................................................................................................. 53
 
Canada .............................................................................................................................................. 53
 
Appendix B: Research papers on the impacts of recreational cannabis laws ...................................... 54
 
Appendix C: Additional trend data ........................................................................................................ 69
 
Prevalence ......................................................................................................................................... 69
 
Hospital and poison control centres .................................................................................................. 73
 
Traffic fatalities .................................................................................................................................. 75
 
Arrests for cannabis possession and supply offences ...................................................................... 76
 
Acknowledgements
The EMCDDA would like to thank Bryce Pardo, Beau Kilmer and Rosalie Liccardo Pacula, RAND
Europe/RAND Drug Policy Research Center for authoring this report. The EMCDDA is also grateful
to Rebecca Jesseman, Director of Policy, CCSA and members of the EMCDDA Scientific Committee,
who reviewed and provided comments on the manuscript.
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TECHNICAL REPORT
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
Executive summary
Over the past 50 years, several jurisdictions in Europe, Australia and the Americas have reduced the
penalties associated with using or possessing small amounts of cannabis. As of December 2019,
Canada, Uruguay and 10 US states have gone further and passed laws that license the production
and retail sale of cannabis, mostly by private companies, to adults for non-medical — sometimes
referred to as recreational — purposes (
1
). With discussions about alternatives to cannabis
prohibition becoming more
common in some parts of the world,
there is a growing interest in learning
from the cannabis policy changes in the Americas.
To learn more about these new cannabis regimes and their consequences, the European Monitoring
Centre for Drugs and Drug Addiction (EMCDDA) commissioned a review of the changes governing
recreational cannabis policies in the Americas and an overview of preliminary evaluations. Findings
from this research are intended to inform discussions about the development of a framework for
monitoring and evaluating policy developments related to cannabis regulatory reform. Key insights
include the following.
In addition to the populations of Canada and Uruguay, more than 25 % of the US population
lives in states that have passed laws to legalise and regulate cannabis production, sales and
possession/use for recreational purposes. In the US, allowing licensed production and sales
is often at the discretion of sub-state jurisdictions, which may impose further zoning
restrictions on cannabis-related activities. This variation can complicate analyses that attempt
to compare legalisation and non-legalisation states, especially when the outcome data are not
representative at state level.
The peer-reviewed literature on cannabis legalisation is nascent, and we observe conflicting
results depending on which data and methods are used, as well as which implementation
dates and policies are considered. It is important to remain sceptical of early studies,
especially those that use a simple binary variable to classify legalisation and non-legalisation
states. This scepticism should extend to the many studies that fail to account for the existence
of robust commercial medical cannabis markets that predate non-medical recreational
cannabis laws. Even if a consensus develops on certain outcomes, it does not mean that a
relationship will hold over time. Changes in the norms about cannabis use and potentially
other substances, the maturation of markets and the power of private businesses (if allowed)
could lead to very different outcomes 15 or 25 years after recreational cannabis laws have
passed. Evaluations of these changes must be considered an ongoing exercise, not
something that should happen in the short term.
One area in which there seems to be a consensus — so far — is with respect to cannabis-
involved hospitalisations and emergency department (ED) visits in Colorado. While studies
have observed increases in the number of adverse events after changes in medical or
recreational supply, they tend to utilise a simple pre-post design without a control group.
Thus, they do not produce causal estimates, and it is possible that some increases could be
due to changes in reporting or measurement. For example, it is unclear if increases in the
number of ED visits and hospitalisations are due to a greater willingness on the part of
individuals to report the use of cannabis and/or if doctors are more aware of acute cannabis
intoxication after the policy change and are now more likely to screen or confirm with
urinalysis.
One insight arising from the evaluations of the regulatory changes in the Americas to date is
the importance of the amount and range of data collected before the change; simply
( ) Two other US jurisdictions, the state of Vermont and the District of Columbia, also allow the cultivation and possession of
cannabis for adults but do not permit its commercialization.
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
comparing past-month prevalence rates will not tell us much about the effect of the change on
health. While US jurisdictions have been moving quickly to legalise the use of cannabis, the
data infrastructure for evaluating these changes is limited. In contrast, Canada has made
important efforts to field new surveys and create new data collection programmes in
anticipation of legal changes. This highlights the importance of any jurisdictions that are
considering changes to the regulatory framework for cannabis starting to think about
improving data collection and analysis systems in advance.
While there is much to learn from what is happening in the Americas, policy discussions
should not be limited to approaches that have been implemented there. There are several
regulatory tools (e.g. minimum pricing, potency-based taxes) that receive very little attention
— if any — that could have important consequences for health, public safety and/or social
equity. It needs to be recognised that all decisions of this nature involve trade-offs and
acknowledging that individuals (and governments) have different values and preferences for
risk when it comes to cannabis policy is important for productive debates on this controversial
topic.
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TECHNICAL REPORT
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
Foreword
The EMCDDA exists to facilitate an evidence-informed understanding of issues that are important for
developing better drug-related policies and actions across Europe. In our series of reports,
Cannabis:
controversies and challenges,
we focus attention on an illicit drug with a long history of use that has
recently been an area of rapid policy development and intense European and wider international
drug policy debate.
In
some countries, questions on what constitutes an appropriate policy response
to cannabis have become both
more
topical and important.
The aim of this set of publications is to
explore, in an objective and neutral manner, some of the complex issues that exist in this fast-
changing area.
The paper
Medical use of cannabis and cannabinoids: questions and answers for policymaking,
published in December 2018, provided an overview of developments in the way in which countries
and jurisdictions are regulating the use of cannabis and cannabinoids for medical purposes. In this
report, the latest in the series, the focus is shifted to recent changes to regulatory systems in the
Americas that permit the consumption of cannabis by adults for non-medical, recreational purposes.
In order to improve our understanding of these new cannabis regimes and their consequences, the
EMCDDA commissioned RAND Europe and the RAND Drug Policy Research Center to undertake a
review of the changes to recreational cannabis policies in the Americas and produce an overview of
the evidence emerging from preliminary evaluations.
At this stage the evidence base is still insufficient to comment with any certainty on the impact of the
changes that are occurring in the Americas. However, this is a rapidly developing area and this
review provides a detailed summary of the current evidence base. The EMCDDA will continue to
follow up on developments to help inform the European debate in this area.
Importantly, this review, in addition to providing EU audiences with a clearer picture of the
developments occurring in the Americas, also highlights some of the challenges associated with
monitoring and evaluating regulatory changes in the drugs field. We trust that this report will be of
particular use to those involved in planning or evaluating any changes to cannabis regulation.
Alexis Goosdeel
Director, EMCDDA
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TECHNICAL REPORT
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
1.
Introduction
The cannabis policy landscape in the Americas is dramatically changing. Individual states in the US
began liberalising their cannabis laws as far back as the 1970s, when several of them reduced or
removed criminal penalties for possession of small amounts of cannabis. Starting in the 1990s, US
states began to allow individuals to possess cannabis for qualified medical conditions. In contrast to
subsequent European systems, medical cannabis in the US was primarily voter initiated and allowed
people to grow and smoke non-standardised cannabis herb for a wide range of medical indications.
These early medical cannabis reforms maintained state-level prohibition, except for a class of patients
who obtained recommendations from authorised medical practitioners.
Distinct from, and in marked contrast to, these earlier medical cannabis reforms, voters in the US
states of Colorado and Washington passed ballot initiatives in 2012 to repeal the prohibition on adult,
non-medical cannabis and to license for-profit firms to produce and sell the drug to adults aged 21
years and over. Since the 2012 election, 10 more US jurisdictions have approved commercial models
for non-medical cannabis, and in two others (Vermont and the District of Columbia — DC) non-
commercial approaches have been adopted.
However, reforms to cannabis supply laws in the Americas are not limited to the US. In late 2013,
Uruguay became the first country in the world to repeal prohibition on cannabis supply for non-
medical markets; however, its approach is more restrictive than the regulated commercial regimes
adopted in the US. Registered adults in that country could begin growing a small number of plants at
home or join a social club in late 2014; by mid-2017, individuals could buy rationed amounts of
cannabis, grown by state-authorised producers, in licensed pharmacies that chose to sell it. In June
2018, Canada became the second country to legalise cannabis production and supply for non-
medical purposes; retail stores opened in some provinces, starting in October 2018. In addition, other
countries in the Americas have passed laws to permit access to cannabis or cannabis-derived
products for medical purposes.
Apart from the regulatory changes in the Americas, which are the focus of this report, changes are
occurring globally. For example, the Dutch government is implementing its 2017 commitment to
experiment with a closed supply chain to coffee shops, while Malta’s government has taken steps to
launch a national debate on whether or not there could be recreational cannabis use, and how this
should be implemented. In 2018,
the parties forming the government of
Luxembourg
reached an
agreement that may allow
for
the future sale of
cannabis to residents, while the highest courts in
South Africa and Georgia have initiated reforms based on human rights that permit the consumption
of cannabis in private settings, but not its sale. Other countries have not formally legalised cannabis
but may have reduced the emphasis that they place on control or introduced some formal or informal
tolerance for personal use of the drug.
The focus of this report is on changes that are relevant to recreational cannabis, sometimes referred
to as adult or non-medical cannabis, with an emphasis on the implementation of commercial models
in US states. The report does not separately evaluate medical cannabis reforms in the US or
elsewhere. These are discussed only insofar as they help to explain the context in which subsequent
recreational cannabis reforms took place. Cannabis and cannabinoids are made available for medical
use in a wide variety of ways; hence the term ‘medical cannabis’ can be used to describe many
different products and forms of supply. For reviews of the evidence on the various medical regimes,
see Pacula and Smart (2017), the EMCDDA (2018) report
Medical use of cannabis and cannabinoids
— questions and answers for policymaking
and the accompanying summary of reviews (Hall, 2018).
Similarly, this report does not examine reforms aimed at reducing criminal penalties for possession or
use but focuses on the broader set of policy changes aimed at regulating the recreational cannabis
market.
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
To learn more about these new cannabis regimes and their consequences, the EMCDDA
commissioned a review of changes governing recreational cannabis policies in the Americas and an
overview of preliminary evaluations. Findings from this research are intended to facilitate a better
understanding among the EU audience of developments occurring in the Americas and to inform
discussions about the framework necessary for monitoring and evaluating policy developments
related to cannabis policy changes that might increase the availability of this substance within Europe.
This report is structured as follows: following this introduction, Section 2 provides the background to
and context of recent developments in cannabis policies in the Americas, with a particular focus on
the more mature state commercial markets in the US; Section 3 offers a description and typology of
different policy approaches with supporting case summaries; Section 4 presents an assessment of
early evidence of the impact of policy changes in this area; and Section 5 provides guidance for
European policymakers considering regulatory changes in the cannabis area on the establishment of
a comprehensive, monitoring and evaluation framework. Appendix A highlights some of the ongoing
and planned studies of legalisation implementation and its consequences in the Americas.
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
2.
Background to cannabis policy developments in the Americas
Changes in cannabis policy that introduce greater tolerance can take various forms. Countries in
Europe and elsewhere have reduced penalties for low-level offences, have removed criminal
sanctions for possession or use or have introduced formal or informal procedures that reduce the
likelihood of sanctions being applied for some forms of personal possession or use. However, up to
now these policy changes have taken place within the overall context of maintaining the prohibition of
cannabis supply and not establishing a regulated market for the drug for recreational users. This is an
important distinction, because efforts to repeal prohibition and replace it with rules governing
production, distribution and possession/use of cannabis are expected to have a greater impact on
public health and safety than amending laws related to possession or use. However, many
jurisdictions in the Americas have begun to repeal the prohibition of cannabis, allowing licensed
businesses to produce and supply it for a narrow set of qualified medical patients (i.e.
medical
cannabis)
or any adult over a minimum age (i.e.
recreational cannabis).
The main focus of this report
is on recent efforts aimed at replacing cannabis prohibition with regulated regimes that permit
recreational cannabis. However, some information relating to medical cannabis regimes is also
provided, as they have been a very common step in the evolution of cannabis regulatory
developments in the Americas (Kilmer and MacCoun, 2017) and are therefore relevant to
understanding the context of subsequent reforms in relation to recreational cannabis use.
The move towards changing cannabis laws to allow medical access is driven by multiple factors.
Three common arguments are (1) the desire to improve the lives of patients who could immediately
benefit from these products, particularly when they are produced in a manner that can ensure
consistency and quality; (2) the desire to learn more about the medical benefits and risks of these
products; and (3) the desire to take action to soften prohibition and improve civil liberties. Another
driver of change that is becoming increasingly important in some jurisdictions is the desire to generate
legal economic activity and tax revenues from cannabis businesses (Subritzky et al., 2016; Hall and
Kozlowski, 2018).
It is also important to consider these medical laws when thinking about the move towards legalising
recreational cannabis. As Table 2.1 makes clear, only a small minority of countries that allow medical
cannabis have made the move towards permitting adults to access cannabis for recreational
purposes. In contrast, Uruguay did not start developing a medical programme until after legislation for
recreational cannabis was passed. This legislation was pushed by the government largely to reduce
drug-related crime and violence associated with the cannabis trade (Aguiar and Musto, 2015).
Despite its initial unpopularity with the citizens of Uruguay (Garat, 2015), it was signed into law in
December 2013.
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
TABLE 2.1
Changes to cannabis supply laws in the Americas
Country 
Implemented
nationally 
Year
passed 
Comments 
Medical 
United States 
No 
1996
onwards* 
In total, 33 states and DC have passed laws to allow cannabis flowers and other
products to be produced and distributed for qualifying conditions. Thirteen other states
allow physicians to recommend or individuals to obtain CBD oils, but do not necessarily
permit their production. This all remains illegal under federal law. 
Currently, all medical cannabis is supposed to be produced by federally licensed private
companies and delivered by post. Efforts are being made to eliminate the illegal
dispensaries that still operate in some jurisdictions. Registered patients may also
cultivate a limited amount at home for their own personal needs. 
Production is licensed by state, and extracts are available in pharmacies for those with a
physician’s prescription. Currently products containing CBD and a low THC
concentration are available for a set of conditions. 
There is limited access to cannabis-derived products approved by health authorities,
which currently include only imported high-CBD/low-THC oils available in pharmacies.
There is an ongoing pilot project with one domestic cultivator.
Licences have been granted since 2017. As at mid-2018, there are a handful of
cultivators and processors as well as two medical dispensaries. Regulations allow small-
and large-scale production of medical cannabis for residents as well as tourist and export
markets. 
The decree signed in December 2015 permits medical cannabis under the national drug
law. The decree was superseded by law. The Ministry of Health has licensed cultivators,
although it is unclear how much cannabis production will be permitted. The law and
accompanying regulations focus on export markets. 
The health agency resolution allows the importation of cannabis oils for epilepsy and
multiple sclerosis.
A law and a ministerial decree have directed the Ministry of Health to draft regulatory
guidelines to allow the state to produce and patients to inscribe into a programme to
obtain or import cannabis oils and other derivatives for treatment of qualifying conditions.
A legislative act and regulatory decree were passed in 2017 to permit the importation of
medicinal products to treat qualifying conditions. Regulations have not yet been finalised.
A law was passed to guide the Ministry of Health with regard to drafting appropriate
regulations to allow doctors to prescribe and patients to obtain cannabis and cannabis
derivatives.
Recreational**
United States 
No 
2012* 
Ten states have passed laws to allow for-profit companies to produce and sell cannabis
(Alaska, California, Colorado, Illinois, Massachusetts, Maine, Michigan, Nevada, Oregon
and Washington) to anyone aged 21 years and over; DC and Vermont allow only home
production and sharing of cannabis. Production and possession remain illegal under
federal law. 
Residents aged 18 years and over must register with the government to either grow
cannabis at home, join a collective or purchase cannabis from pharmacies. Home
growing of cannabis and social clubs started operating in the latter half of 2014. State-
licensed companies produce retail products sold in pharmacies. Sales began in mid-
2017. The government determines the price and potency of cannabis sold in
pharmacies. Pharmacy sales have slowly been introduced, partly because of issues
pertaining to the access of financial institutions with branch offices in the US. 
In mid-2018, the Canadian parliament passed the Cannabis Act to permit adults to
cultivate, process and use cannabis for recreational purposes. The law came into effect
in October 2018. Under the law, the provinces are given regulatory power with regard to
distribution, but federal law provides general rules on production, promotion, packaging
and licensing.
Canada 
Yes 
2001 
Uruguay 
Yes 
2013 
Chile
Yes
2015
Jamaica 
Yes 
2015 
Colombia 
Yes 
2015 
Brazil
Argentina
Yes
Yes
2016
2017
Mexico
Peru
Yes
Yes
2017
2017
Uruguay 
Yes 
2013 
Canada
Yes
2018
* Federal law still prohibits cannabis. The date reflects the date when the first state passed a law.
** In October 2018, the Mexican Supreme Court ruled that prohibiting cannabis for personal use is unconstitutional; however, this does
not technically legalise use and supply. The legislature is working to amend the law, to codify the ruling. For more information, see Lopez
(2018).
THC, tetrahydrocannabinol — the principal intoxicative agent in cannabis; CBD, cannabidiol — a cannabinoid that has the potential to
reduce certain maladies and attenuate some of the effects of THC.
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
Most of the changes have been limited to supplying cannabis for medicinal purposes, and there is an
important variation in what these legal frameworks allow. These regulatory systems and the products
that are available to patients differ from traditional medicinal formulations that contain synthetic
cannabinoids (e.g. dronabinol or nabilone) or plant-derived preparations approved by the government
(e.g. Sativex or Epidiolex). Some jurisdictions make it easy for patients to access a myriad of
cannabis preparations, including raw or herbal products that can be smoked or vaporised (e.g. many
US states, Canada), as well as various cannabis-derived preparations, such as vaporisable
concentrates, tinctures, edibles and topicals. More restrictive markets only allow cannabis extracts
with high levels of cannabidiol (CBD) and a trace or modest amounts of tetrahydrocannabinol (THC)
(e.g. about a dozen US states, Chile, Brazil, Mexico) or limit the types or forms of cannabis available
to patients (e.g. prohibiting smoking of herbal or raw cannabis).
However, in US states, recreational legalisation has followed the provision of medical cannabis, and
multiple hypotheses have been offered about how the latter may have smoothed the transition to the
former. Kilmer and MacCoun (2017) offer five potential explanations for the transition:
(a) it demonstrated the efficacy of using voter initiatives to change cannabis supply laws;
(b) it enabled the psychological changes needed to destabilise the ‘war on drugs’ policy stasis;
(c) it generated an evidence base that could be used to downplay concerns about non-medical
legalisation;
(d) it created a visible and active cannabis industry;
(e) it revealed that the federal government would allow state and local jurisdictions to generate
tax revenue from cannabis.
Of course, some of these reasons are specific to the US (e.g. state ballot initiatives and federalism).
With respect to the visibility of the cannabis industry, Kilmer and MacCoun (2017) note the following:
The proliferation of medical dispensaries in the 2000s introduced the public to the idea of
stand-alone stores selling [cannabis] products (and not just to those residing in states that
allow medicinal [cannabis], as dispensaries are regularly featured in media stories across the
country). Subsequent advertisements in alternative weekly newspapers and occasionally on
billboards also exposed voters to this new quasi-legal industry.
Of course, not everyone is thrilled with the establishment of medical dispensaries and the
related advertising, and there is tremendous variation in what states allow and how they are
regulated (Pacula et al. 2015). Further, even in states that allow dispensaries, some local
jurisdictions have decided to prohibit them. But for those who see these dispensaries on a
regular basis, they not only have a sense of what legalisation may look like but also may be
desensitised to the idea of retail [cannabis]. In fact, some may conclude that allowing any
adult to enter those stores instead of only those who have recommendations — which in
some states are very easy to obtain (e.g., High Times 2016) — may not be a big change.
Medical [cannabis] laws also created an industry looking to expand its market beyond medical
patients. Indeed, it is hard to imagine that some of those developing, e.g., brands, new
methods of ingestion, and improved production methods did not have their sights on a larger
market. Although those in the advocacy community criticised the industry for not donating
more to the campaigns (e.g., see quotes from Ethan Nadelmann in Freedlander 2016), some
with a financial interest did make contributions.
In Canada, a series of provincial and Supreme Court cases during the early 2000s gradually legalised
the medical use of cannabis. The initial medical system developed at the national level slowly
unfolded. In 2001, Canada enacted enabling legislation via the Controlled Drug and Substances Act
to pass the Marihuana Medical Access Regulations (MMAR). This new set of regulations permitted
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
individuals with qualifying illnesses (which were listed by the regulation) to obtain medical cannabis.
The initial programme was overly restrictive, so that many patients wishing to take cannabis for their
condition had to source it from the illicit market (Fischer et al., 2015). Individuals were allowed to
obtain cannabis by three different means: (1) by applying to access Health Canada’s supply of dried
cannabis via the postal system; (2) by applying for a personal-use production licence (i.e. to grow
cannabis at home); or (3) by designating someone to cultivate on their behalf with a ‘designated-
person production licence’. This last provision was criticised for permitting unregulated and outright
illicit sales (Fischer et al., 2015).
In response to concerns from law enforcement and other policymakers that the system governed by
the MMAR was open to abuse, and after extensive consultations, the Harper government introduced
the Marihuana for Medical Purposes Regulations (MMPR) in 2013 to further restrict and regulate the
market by eliminating home-growing of cannabis and limiting designee production. Under the MMPR,
only licensed producers could cultivate medical cannabis. Justin Trudeau became prime minister in
2015 and prioritised cannabis policy reform, including the legalisation of recreational cannabis. In
2016, the MMPR was struck down on constitutional grounds and was later superseded by the Access
to Cannabis for Medical Purposes Regulations (ACMPR), which built on the existing framework for
licensed commercial producers established under prior regulations while permitting patients to register
to cultivate a small amount for personal medical use. Existing producers licensed under the ACMPR
would later be deemed as such under the Cannabis Act.
While bricks and mortar medical dispensaries (
2
) were technically illegal under Canadian law, some
jurisdictions allowed them to operate; other jurisdictions, such as Vancouver, eventually established
some licensing and regulatory frameworks to control the growing retail industry (Johnson, 2015). As in
multiple US states, this probably introduced some Canadians to the idea of stand-alone stores selling
cannabis products as well as advertising such products. Many Canadian medical cannabis producers
anticipated supplying the much larger recreational market. As cannabis is federally legal in Canada,
some of these Canadian firms are listed on major US stock exchanges, in contrast to firms from the
US, and some investors believe that they are ‘poised to surge’ (Chang, 2018). Yet projections of
earnings and market valuation have been revised downwards, as sales have not met analyst
expectations (Subramaniam, 2019).
Another important difference between Canada and most of the US states that have legalised
recreational cannabis is the amount of public discussion and deliberation that took place before the
policy change (
3
). After Prime Minister Trudeau announced his party’s intentions to legalise cannabis,
the Liberal government convened a task force that would spend nearly a year collecting information
about regulating cannabis from several sources, ranging from international experts to domestic
cannabis users. The task force’s resulting report was released in December 2016. The report and
subsequent recommendations helped shape the legislation introduced in April 2017. Soon after, there
were several hearings in parliament about the bill. In the Senate’s Standing Committee on Social
Affairs, Science and Technology alone, there were 18 hearings. After more than 1 year of
deliberation, the final bill received Royal Assent in June 2018, and legal sales began on 17 October
2018.
( ) Shops with a physical location, as opposed to online or virtual businesses.
( ) The most obvious exception is Vermont. Since 2014, the state legislature has seriously deliberated various legalisation
proposals, from commercial models to the grow-at-home model, the latter being implemented in 2018. Other state authorities
have commissioned expert reports assessing the impacts of legalisation (e.g. California) (Caulkins et al., 2015; Newsom et al.,
2015).
3
2
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3.
A description and typology of different policy approaches
Jurisdictions considering alternatives to prohibition on cannabis supply are faced with a wide range of
options from which to choose. Figure 3.1 presents some alternatives to the status quo prohibition of
cannabis supply, including eight ‘middle-ground’ options between traditional prohibition and the
standard for-profit commercial model, which is being adopted in an increasing number of US states.
However, as will be made clear in this section, the for-profit option is not the only option that is
pursued in the US, and both Uruguay and Canada have created regulatory regimes intended to limit
the power of businesses.
It is also the case that these options are not mutually exclusive. Jurisdictions can allow both home
production and commercial sales, a scenario that has occurred in most places that have legalised
cannabis. Furthermore, the choices need not be the same at the various levels of cannabis markets
(Wilkins, 2016). For example, it is possible to allow commercial businesses to produce cannabis but
require that its distribution occurs via state-run retail stores, as is the case with alcohol in some
jurisdictions, or via postal delivery, as is done in some parts of Canada.
FIGURE 3.1
Some alternatives to status quo cannabis supply prohibition
Source: Caulkins et al., 2015
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3.1
US approaches
More than 25 % of the US population lives in 10 states where voters have passed laws permitting the
commercialisation of cannabis production and distribution. Table 3.1 reports dates of passage for both
medical and recreational legalisation as well as when retail dispensaries began selling recreational
cannabis to adults.
While the commercial models in Colorado, Washington and California receive a great deal of
attention, not all US states that have legalised cannabis have allowed commercial sales. Both DC and
Vermont have opted for non-commercial access, allowing adults to privately grow and give away up to
an ounce (28 g) of cannabis. In 2014, DC voters approved Initiative 71, which permits adults to grow
up to six plants and to give away cannabis without remuneration (
4
). The law maintains a prohibition
on selling cannabis and made public consumption a minor offence. The initiative has not been
formally evaluated, but early media reports suggest that the new law has spurred unregulated
transactions under the guise of giving cannabis to someone as a gift (Garcia, 2017).
In addition to DC, the state of Vermont legalised recreational cannabis in January 2018, which came
into effect on 1 July of the same year. After more than two years of legislative deliberation and a
government-sponsored report on the options and issues regarding legalisation, Vermont became the
first state to repeal cannabis prohibition through legislation, rather than an initiative approved by
voters. Similar to DC, Vermont’s law permits adults aged over 21 years to grow six plants (up to two in
flower) and to possess or give away up to an ounce of herbal cannabis. It does not permit sales. As in
the case of DC, ‘grey market’ sales of cannabis, though technically illegal, may be occurring in
Vermont’s unregulated non-commercial system (Goldstein, 2018).
TABLE 3.1
Passage of recreational and medical cannabis laws in US states that permit these
State
Alaska
California
Colorado
DC
Illinois
Maine
Massachusetts
Michigan
Nevada
Oregon
Vermont
Washington
Medical cannabis law
passed*
1999
1996
2000
2010
2013
2002
2013
2008
2000
1998
2004
1998
Recreational cannabis
law passed
4 November 2014
8 November 2016
6 November 2012
4 November 2014
25 June 25 2019
8 November 2016
8 November 2016
6 November 2018
8 November, 2016
4 November 2014
22 January 2018
6 November 2012
Start of recreational
sales
29 October 2016
1 January 2018
1 January 2014
Not applicable
Not yet open
Not yet open
20 November 2018
2 December, 2019
1 July 2017
1 October 2015
Not applicable
8 July 2014
*Medical cannabis laws have varied over the years. Here, we report the first year in which the state adopted a
medical cannabis law, not necessarily when voters approved the initiative. Initially, these laws permitted
qualifying individuals to possess cannabis. Over time, dispensaries and collective cultivation sites sprung up to
supply growing patient demand. Since their inception, states have adopted various regulatory approaches,
formalising commercial medical markets.
Source: National Conference of State Legislatures (2019)
( ) Many but not all jurisdictions in the US allow citizens to propose initiatives for consideration by voters provided they obtain
enough signatures.
4
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3.2
Uruguay
In 2013, Uruguay became the first country in the modern era to legalise recreational cannabis use.
Under the law, resident adults aged over 18 years can register with the state regulatory authority to
access cannabis through one of three available supply channels. Registrants can switch from one
supply channel to another, after changing their status with the regulatory authorities. Regardless of
which supply stream users opt into, they are technically limited to 480 g per year. The three types of
access are home cultivation, membership at a cannabis social club or retail sale via licensed
pharmacies.
Individuals who decide to grow cannabis at home cannot cultivate more than six plants. As of May
2019, there were some 7 000 registered home growers. Clubs are limited to 45 members and can
cultivate only up to 99 plants. Currently, there are 119 clubs in operation across the country, servicing
about 3 600 members. Registered members are prohibited from obtaining more than their allowance
of 480 g. Those opting to purchase at pharmacies must also register with authorities and are limited to
purchasing no more than 10 g per week, with an annual cap of 480 g. There are just a few varieties of
the plant on offer at pharmacies (i.e. regulators currently limit retail pharmacy sales to only a few
strains), and authorities have aimed to keep potency below 10 % THC. According to regulators, there
are currently 17 licensed pharmacies, mostly in the capital region, that sell cannabis to about 36 000
registered adults (
5
). There are no taxes on retail sales, but the government has set a price of UYU 40
(about EUR 1) per gram.
3.3
Canada
As a federal system, the new recreational cannabis law removes most prohibitions on cannabis from
national drug control statutes (criminal prohibition on supply to or possession by minors or
unregulated production remains). In most provinces, adults aged over 18 years can possess up to
30 g of herbal cannabis (or its equivalent in weight in other forms, such as concentrates (
6
)). The law
allows the cultivation, distribution and possession of cannabis by government-authorised entities.
Federal law provides standards and a general framework for regulating cannabis, including
requirements for an inventory tracking system, fees, quality and testing rules, restrictions on labelling
and packaging, prohibitions on promotions aimed at enticing young people and bans on the types of
products for sale. Federally licensed producers can be publicly traded, for-profit businesses, and
there are no restrictions on alcohol and tobacco companies receiving a production licence.
Though the federal government has lifted prohibition, provinces have considerable power in designing
rules governing distribution, taxation, and establishing age limits for purchase (some provinces opted
to increase the minimum age to 19 years). Provinces are also tasked with enforcing their own
regulations. Though federal law permits adults to cultivate up to four plants at home, some provinces
have banned home cultivation. Provincial retail systems are still evolving, with some opting for public
distribution channels similar to government-run alcohol stores.
What distinguishes Canada from the US states that have legalised cannabis is that the federal
government led the effort to repeal prohibition, with the aim of reducing youth access, protecting
public health and improving public safety by shrinking the illicit market. Unlike states in the US,
Canadian provinces do not maintain their own competing criminal drug laws. Another important
variation found in Canada’s law is that it allows for mail order supply of cannabis, minimising the need
for bricks and mortar stores. The federal government is also committed to public health and education
campaigns aimed at reducing problematic use, including underage use.
( ) See
https://www.ircca.gub.uy/farmaciasadheridas/
( ) Under Canadian law, 0.25 g of concentrates is equivalent to 1 g of dried herbal cannabis, and 15 g of solids containing
cannabis is equivalent to 1 g of dried herbal cannabis.
6
5
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4.
An assessment of early evidence of the impact of policy
changes in the United States
This section summarises the early evidence of the consequences of policy changes concerning
recreational cannabis laws in the US. Here, we focus on the commercial cases that are specific to the
US, given that these policy changes have unfolded over longer time periods, allowing for more
evaluations of their impacts. They are also likely to have larger social impacts than non-commercial
reforms such as home cultivation. Recreational cannabis laws are frequently referred to as
‘recreational marijuana laws’ and ‘medical marijuana laws’, as in US statutes and regulations
cannabis is more commonly referred to as ‘marijuana’. We refer to these as REC (recreational) or
MED (medical) cannabis. Colorado and Washington were the first states in the US to pass REC laws,
followed by Oregon and Alaska. Though other states, such as Maine and Illinois, have passed similar
laws, they have yet to fully implement market regulations, or too little time has passed since they have
been in place to allow the evaluation of the impacts. This analysis largely focuses on the pioneering
states of Colorado and Washington, where more time has passed and more data have been
collected.
Though REC laws have existed only in the last seven years, their adoption follows the passage of
MED laws and, in some cases, robust commercial markets (see discussion in Section 2). The
variation in MED laws and associated outcomes has been documented in scientific literature (Cerdá
et al., 2012; Hasin et al., 2015; Pacula et al., 2015; Hall, 2018); as a result, we do not assess MED
laws or their policy impacts here.
The consequences of the REC legal changes analysed here are likely to vary depending on the
design and implementation of pre-existing medical cannabis laws and the size and scope of state
commercial markets. For example, jurisdictions with commercial medical markets, lax restrictions on
patient access and minimal regulatory burdens may not observe as many post-REC changes as
states that restricted medical access to a narrow set of qualifying conditions or limited the number of
dispensaries (
7
). In some cases, the adoption of REC laws is a marginal change (Colorado and
California had large, loosely regulated medical markets for more than a decade before the adoption of
REC laws, and the regulation of medical markets in Washington state did not occur until after the
passage of REC laws); for other states, recreational laws are more novel (Massachusetts and Maine
have had smaller or limited commercial medical markets for shorter time periods).
An assessment of the adoption of REC laws (and MED laws before them) must consider the
underlying economic and social trends. Legalisation — but more importantly commercialisation — is
likely to affect social norms by promoting use, normalising behaviours, increasing availability,
introducing new products and lowering price (Caulkins et al., 2015; Hall and Lynskey, 2016; Subritzky
et al., 2016; D’Amico et al., 2018). The extent to which any or all of these consequences resulted in a
net benefit or net cost to society is unclear. Nevertheless, many consequences may depend on the
timing of REC legalisation and its implementation and the shape in which both unfolded. Therefore,
examining changes in commercial access (e.g. when stores opened) is perhaps a more accurate
exposure variable than the date when a law was adopted. In addition to timing, an ideal measure for
REC exposure should account for retail store density, something most of the literature has omitted in
its analysis.
( ) As the US federal government maintains the scheduling of cannabis as a Schedule I drug and because pharmacies require
a federal licence to distribute controlled substances for medical purposes, medical cannabis products cannot be distributed
through traditional pharmacies, even in states that permit cannabis for medicinal use. This is, in part, how and why the
cannabis dispensary system started in the US.
7
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4.1
Literature review selection criteria
We reiterate that the contemporary literature base on REC law impacts is thin, given that policies are
still developing, markets are still maturing, and there are significant data gaps. Furthermore, states
are adopting these legal changes against a backdrop of federal prohibition. Therefore, the full extent
of these effects may change considerably in an environment in which the substance is legal at the
national level (e.g. in Canada or Uruguay). Interstate trade and federal tax policy could have broad
implications on the outcomes assessed here. Looking to the future, the immediate outcomes
evaluated in this review may not reflect long-term outcomes, which may take decades or longer to
develop. We therefore urge caution when interpreting the short-term measures and findings reported
below.
That said, we assessed the emerging evidence on the outcomes of REC law changes. We excluded
studies specific to MED, though the context of REC adoption and design is relative to a state’s
medical framework. These underlying legal and social factors related to MED may extend to
differences in the outcomes reported post REC adoption. We also note that many studies specify
various policy interventions, sometimes unclearly. Several peer-reviewed articles focus on REC
enactment (after a law was passed to effect a change; in most cases, the prohibition on possession or
home cultivation was lifted before implementation) or REC implementation (once the law is in effect
and retail stores are open). Some ignore the distinction entirely, blending the two, rather than
evaluating impacts in policy change after enactment or implementation.
We prioritise peer-reviewed articles over the grey literature or reports published by advocacy groups,
but we have included a few well-designed working papers. In terms of the research design of articles,
we highlight findings from quasi-experimental studies that include a control group or employ an
interrupted time series method to assess policy impact (
8
). Studies that use state representative
samples are prioritised over studies that have a non-representative or convenience sample. We also
avoided including studies that evaluate measures at only one point in time or fail to include measures
from pre- and post-implementation periods. Study design and methodology were an important
component of this analysis. Our initial scan of the literature yielded many methodologically weaker
studies that assessed outcomes of interest but were excluded for further review because they did not
meet our methodological selection criteria. We have included all studies captured in our search in
Appendix B, but we only assess outcomes of more rigorous studies in the body of this review.
Our search strategy focused on databases of peer-reviewed articles and working papers. We
searched Google Scholar and PubMed for peer-reviewed articles in English and the National Bureau
of Economic Research for working papers. We identified papers written and/or published up until July
2018, focusing on REC legalisation in the Americas; in addition six more recent peer-reviewed
publications with credible control groups were added to the review during the publication process to
ensure the findings were as up-to-date as possible (Kerr, D. et al., 2018; Anderson et al., 2019;
Aydelotte et al., 2019; Cerdá et al., 2019; Everson et al., 2019; Lane and Hall, 2019) and insights from
a new review (Smart and Pacula, 2019). Given that REC is a recent phenomenon, we concentrated
our screening on articles published after 2012. The following search terms were used:
recreational;
marijuana
or
cannabis;
and
legalisation.
We screened articles, focusing on evaluations relevant to
REC and those that utilised methods that allowed for making inferences (e.g. pre-/post-analyses,
interrupted time series, differences-in-differences).
4.2
Prevalence of use
Some analysts hypothesise that cannabis prevalence rates will change after recreational
commercialisation (e.g. Caulkins et al., 2015; Hall and Lynskey, 2016). There are many reasons for
( ) The one exception was a series of studies looking at adverse events pre/post REC legalisation in Colorado. We opted to
include these studies, as they provide unique assessments of health outcomes relative to MED and REC legislation adoption in
that state.
8
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this, such as changing norms regarding cannabis use behaviours, product innovation, reductions in
price and advertising (if allowed). There is greater concern regarding potential increases in youth
prevalence, given the impacts of cannabis on the developing brain and the finding that early initiation
is associated with poorer outcomes later in life (Fergusson and Boden, 2008). However, the
consequences of REC legalisation will probably depend on how policy is implemented and the degree
to which underlying attitudes and trends may be associated with recent changes in a state’s medical
cannabis policy. In turn, both medical and recreational policy changes may be a latent factor of
underlying social attitudes regarding cannabis. Nevertheless, changes in supply, especially as it
relates to
access
to cannabis through retail establishments and
price,
may have a greater impact on
prevalence than a mere change in the law, which is why several have cautioned that the longer term
effects of liberalisation policies may not be consistent with short-term effects (Caulkins et al., 2015;
Cerdá et al., 2017).
Prevalence estimates are some of the most referenced statistics about the consequences of REC
legalisation. The prevalence of cannabis consumption measures the proportion of a particular
population that self-report using cannabis within a certain period, typically in the last month, in the last
year or during their lifetime. The federal and state governments regularly estimate prevalence rates
for different age cohorts using household or school surveys. The National Survey on Drug Use and
Health (NSDUH) and the Monitoring the Future (MTF) surveys are two well-known, nationally
representative surveys that regularly report cannabis prevalence, frequency of use and perception of
risk estimates by age groups. The NSDUH also reports pooled 2-year, state-level prevalence
estimates by age group. In addition to these surveys, Colorado and Washington (
9
) have conducted
their own state-wide prevalence surveys of high school students (Healthy Kids Colorado Survey —
HKCS; and Washington state’s Healthy Youth Survey — HYS). Our scan of the literature also
identified studies that evaluated changes in other repeated cross-sectional surveys, such as the
National College Health Assessment survey or the National Alcohol Survey.
Figure 4.1 plots the past-month cannabis prevalence rates for the five states that passed REC laws
before 2016 and for the entire country (
10
). Table 4.1 is included as a reference, indicating when
MED/REC laws were adopted and when stores opened (except DC, which remained ‘grow and give’
only). Almost all states report increases in prevalence rates among the general population post REC
legalisation, though prior trends suggest an increase in states’ predated REC laws. Of course, simply
examining trend data does not allow for strong causal inferences, and there is an emerging quasi-
experimental literature attempting to control contextual factors and isolate these policy effects.
TABLE 4.1
Dates of MED/REC adoption and implementation for selected states
Medical cannabis
State
Alaska
Colorado
DC
Oregon
Washington
Adoption
November 1998
November 2000
November 1998
November 1998
November 1998
Year stores legally
opened
Not applicable
2005
2010
2009
Not applicable
Recreational cannabis
Adoption
November 2014
November 2012
November 2014
November 2014
November 2012
Implementation
October 2016
January 2014
February 2015
October 2015
July 2014
( ) We focus on these two states, given that there are more available post-treatment data, because recreational markets have
been operating for over four years.
( ) Additional trend data, including plots for individual states, are included in Appendix C.
10
9
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FIGURE 4.1
Prevalence of cannabis use in the past month (%) among people aged 12 years and older
20
15
10
5
0
2009
2010
Alaska
2011
Colorado
2012
DC
2013
2014
Oregon
2015
Washington
2016
US
2017
Source: NSDUH
So far, the peer-reviewed literature reports mixed findings regarding changes in self-reported
prevalence after the adoption of REC laws. Studies in this nascent literature focused on adults are
more likely to find an increase than those examining younger populations; indeed, there are some
studies suggesting that youth prevalence may have declined. Table 4.2 compiles and summarises
these findings described below.
Youth
In terms of changes among students, Cerdá et al. (2017) reported significant declines in the
perception of harm and significant increases in past-month use of cannabis among 8th and 10th
graders in Washington compared with states that did not adopt REC laws. The study employed a
difference-in-difference approach to compare past-month prevalence rates between 2010-12 and
2013-15 in Colorado and Washington against rates in the rest of the US. The authors found that, in
Washington, perception of harm reduced by 9 % for both grades (p < 0.02) and that past-month use
increased by 5.0 (p = 0.03) and 3.2 (p = 0.007) percentage points for 8th and 10th graders,
respectively (Cerdá et al., 2017). However, no significant difference in perception or use was reported
for 12th graders in Washington or for any of the grades in Colorado.
The study treated REC enactment and implementation as one policy change. Though the law
changed after voters approved the initiatives, stores were not authorised to sell cannabis products to
customers until after the implementation. The different trends in prevalence may also be an artefact of
the different nature of the medical cannabis policy environments in Washington and Colorado, the
latter having a robust commercial market and allowing un-registered caregivers to cultivate a large
number of plants for registered patients. This finding may also be an artefact of the data used. Using
survey data from a much larger sample of students in Washington (Washington’s Healthy Youth
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Survey; HYS), Dilley et al. (2019) found that, if anything, there was a decrease in the past-month
prevalence among 10th-grade students in Washington after REC enactment, according to state-wide
surveys. Whether these results hold up when specific subgroups of students are examined remains to
be seen.
Using the individual-level NSDUH data with state identifiers from 2008-2016, Cerdá et al. (2019)
found no evidence that REC enactment influenced the past-month cannabis prevalence for those
aged 12-17. Although it should be noted that only three states (Colorado, Washington and Oregon)
had implemented REC markets with open stores during the period of evaluation, and those had only
been open for a relatively short period of time during their window of evaluation. Anderson et al.
(2019) examined a longer time-frame (1993-2017) using the national and state Youth Risk Behavior
Survey (YRBS) and reported there was no association between MED laws and past-month
prevalence among students; however, they did find evidence suggesting prevalence may have
declined for students after REC laws were enacted (
11
). We expect additional analyses will be
conducted with these datasets that exploit additional changes in implementation of the state laws,
information about per capita outlets and retail sales, and other aspects of the regulatory
environments. The results thus far suggest that the mere passage of the laws does not affect youth.
More research is needed to understand whether youth consumption is influenced by features of more
mature cannabis markets, which are characterised by lower prices, product proliferation, and higher
outlet density.
College students
In two studies of college students, D. Kerr et al. (2017, 2018) investigated changes in cannabis
prevalence rates after REC enactment in Oregon. In their first study, authors collected responses from
online surveys of students (aged 18 to 26) across seven universities, only one of which was in
Oregon, between 2012-2016. Using these repeated cross-sectional surveys, authors found that
cannabis use rates had increased across six of the seven universities over the time period, but the
increase in use rates was significantly greater for students in Oregon that also reported recent heavy
alcohol use (Kerr, D. et al., 2017).
In another study using a different repeated cross-sectional survey of university students (ages 18-26)
from 2008 to 2016, authors compared changes in self-reported cannabis use rates from two
universities in Oregon and 123 universities and colleges from non-REC states. Authors found that,
compared to the students in the other states, Oregon students showed a relative increase in rates of
past-month cannabis use after REC law passage (odds ratio = 1.29 [1.13, 1.48]) (Kerr, D. et al.,
2018).
Adults
W. C. Kerr et al. (2018) analysed self-reported past-year cannabis use in Washington with a repeated
cross-sectional random sample of adults aged 18 years and over from before the state implemented
REC legislation but after it enacted it (wave 1: January to April 2014) and post implementation
(wave 2: March to May 2015; wave 3: August to October 2015). Participants were also asked to recall
their past-year cannabis use for the 12 months prior to REC enactment, which started in December
2012. The authors found that respondents reported a small and non-significant increase in past-year
use (from 24.3 % to 25.6 %) from the responses relating to the pre-enactment period to the combined
average of all three post-enactment/implementation waves (Kerr, W.C. et al., 2018). They go on to
state that there was no statistically significant change in the prevalence of the simultaneous use of
alcohol. However, the study relies on participants’ recall of past-year use, prior to REC law enactment,
which may not be accurate and is likely to be influenced by the state’s medical cannabis market.
11
( ) However, critics have raised concerns about merging national and state-representative samples from the YRBS for
conducting analyses of the effects of any state policy, including medical and recreational cannabis laws. Doing so can lead to
distortions of the sample in some states, which may affect the results obtained using these data (Jones et al., 2019; Rapoport
et al., 2019).
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Furthermore, the study does not clearly distinguish between REC enactment and implementation. The
null effect reported may be due to the study’s design, such as relying on respondents’ memory.
Without a suitable control group for comparison, it is hard to draw strong inferences.
One cohort study analysed self-reported past-year use data from the repeated cross-sectional
National Alcohol Survey of adults across the country between 1984 and 2015. The authors used an
age-period-cohort design to assess changes in respondents’ past-year use across states that passed
REC or MED laws or allowed home cultivation or operational dispensaries. The authors found that the
underlying period effects were the main factor contributing to increases in self-reported cannabis use;
the passage of REC laws, or laws allowing home cultivation of cannabis and the opening of
dispensaries were not significantly associated with increases in prevalence (Kerr, W. C. et al., 2017).
They noted that, though REC/MED policies were not associated with changes in prevalence, survey
data show a decline in use during the 1980s and 1990s but a sharp increase from 2005 to 2015,
varying by demographic and age cohort. The authors attributed recent increases in self-reported
prevalence to general period effects that influence the greater population, rather than specific REC
policies. Nevertheless, the authors noted that their design does not allow for an analysis of state-
specific trends. Furthermore, as their analysis covers a period of more than 30 years, it may be
confounded by changes in social attitudes towards cannabis use. They noted that self-reported use
may be affected strongly by legal and social norms, which might bias responses.
The previously mentioned NSDUH analysis by Cerdá et al. (2019) looking at cannabis use among
youth also examined whether enactment of REC laws influenced the prevalence rates for adults,
broken down into two age groups: 18-25 and 26+. Similar to the findings for those under 18, they
found no effect on the prevalence rates for cannabis use among those 18-25 after REC enactment;
however, the results were different for the oldest group. The authors found that REC enactment was
associated with an increase in the prevalence of past-month cannabis use among those aged 26 and
over (odds ratio [OR], 1.28; 95 % CI, 1.16-1.40).
While the significant within-state variation in how legalisation is being implemented can complicate
state-year panel analyses, it does provide opportunities for learning more about how store density and
other factors may influence cannabis prevalence and other outcomes. Merging information about
recreational store addresses with location information for adults participating in Washington’s
Behavioral Risk Factor Surveillance System from 2009-2016, Everson et al. (2019) found that past-
month cannabis use ‘increased among adults living in areas within 18 miles of a retailer and,
especially, within 0.8 miles (odds ratio [OR] = 1.45; 95 % confidence interval [CI] = 1.24, 1.69).’ Of
course, it would make sense that some stores would try to locate in places with more cannabis users,
and the authors attempted to account for this by estimating generalised mixed models with a random
intercept by community effect and a random time by community effect as well as controlling for a host
of community-level (and individual-level) variables. The authors acknowledge that an important
limitation is that the analysis does not account for the number of unlicensed medical cannabis outlets
or ‘community gardens’ operating in the state before and after the REC law was passed; however,
they argue this may have biased their results toward zero (
12
).
Finally, one study examined self-reported past-month rates of use in two cohorts of pregnant women
and young mothers in an alcohol and drug case management intervention programme before and
after REC law enactment and implementation in Washington (comparing wave 1, February 2001 to
November 2012, with wave 2, December 2012 to July 2015). The authors compared self-reported
past-month cannabis use in samples of participants from nine populous counties in the state and
found that women who completed the programme post REC law enactment (in or after December
12
( ) Everson et al. note: ‘Because we did not account for alternate sources, we overestimated the net proportional increase in
cannabis access attributable to the retail market (although not for the law-abiding general public). Our findings may thus
underestimate the potential effect of introducing retail access as compared with locations with smaller or less easily accessible
medical and illicit markets.’
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
2012) were significantly more likely to report cannabis use on exit (OR = 2.1,
p
< 0.0001) (Grant et al.,
2017). The authors went on to note that women who used cannabis during pregnancy in the post-
REC group were significantly less likely to quit than their counterparts in the pre-REC group (33.1 % v
45.4 %,
p
< 0.01). However, the sample of this cohort study limits interpretability to at-risk young
mothers and pregnant women attending a drug and alcohol outreach programme and does not
include the larger population of young mothers. Furthermore, researchers ignored any different policy
impacts between REC enactment and implementation. The reliance on self-reported data may
introduce bias in a population of individuals referred to a drug and alcohol abuse intervention
programme. The pre-REC population may have under-reported their cannabis use to avoid stigma
and legal sanctions.
The mixed results reported in the literature may be, in part, due to the variation in study design
methods, sub-population selection and which cannabis policy change researchers are measuring over
which time period. As noted, several studies seem to conflate REC law adoption, enactment and
implementation. Even when voters approve a REC initiative, it can be one or two years before any
cannabis is sold in stores. Along with lags in survey data, researchers, eager to evaluate the impacts
of REC, may be incorrectly specifying when a change in policy occurred, particularly given the existing
medical cannabis policies that are in place in all of these states that had legalised REC cannabis.
Furthermore, the time periods analysed may yield different results. The inclusion of long pre-REC
legalisation periods, which pick up the effects of MED cannabis provision, may return different results
from studies over shorter pre-REC periods. Finally, studies that combine young people and adults, or
at-risk populations and general household populations, may fail to pick up important heterogeneous
effects that exist across these populations, as shown in studies examining the effects of medical
cannabis policies (Chu, 2014; Pacula et al., 2015; Wen et al., 2015; Smart, 2016).
In Table 4.2 we summarise the main findings of the four articles examining changes in prevalence
rates post REC introduction that were discussed above. The remainder of the prevalence studies did
not meet our inclusion criteria because of their research design, which lacked a suitable control, or
because they were taken from convenience samples, they were cross-sectional or point-in-time
measures or they failed to compare pre-REC outcomes with post-REC outcomes.
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TABLE 4.2
Summary table of peer-reviewed studies examining the effect of REC laws on cannabis
prevalence
Study
Anderson et
al. (2019)
Cerdá et al.
(2017)
Outcome evaluated
Prevalence rates in high school
students
Perception of harm and youth
prevalence
Policy change
REC/MED enactment
across states
REC enactment and
implementation in
Colorado and Washington
Changes associated with policy
No change in reported use after MED,
possible decline after REC enactment
Reductions in perception of harm and
increases in reported use for 8th and 10th
graders in Washington
No changes in perception or prevalence
among 12th graders in Washington or
young people in Colorado
Cerdá et al.
(2019)
Dilley et al.
(2019)
Everson et
al. (2019)
Grant et al.
(2017)
Prevalence rates and self-reported
cannabis use disorder rates for youth,
young adults, and adults
Prevalence rates for secondary school
students
Prevalence rates for adults
REC enactment in
Colorado, Washington,
Alaska and Oregon
REC enactment in
Washington
REC enactment and
implementation in
Washington
REC enactment and
implementation in
Washington
REC enactment in
Oregon
No changes in prevalence rates for those
ages 18-25. Increase in respondents 26
years or older
Decrease in prevalence rates for 8th and
10th grades
Increase in current use of cannabis for
those that reported proximity to a retail
outlet
Significant increases in self-reported use
Changes in past-month rates of use in
pregnant women and young mothers
in an alcohol and drug case
management programme
Prevalence rates in college students
Kerr, D. et
al. (2017)
No changes in prevalence rates for
students in Oregon. An increase in
cannabis prevalence rates for those also
reporting recent alcohol binge drinking
Increase in cannabis prevalence rates for
students in Oregon
Increases in prevalence are attributed to
underlying age-period-cohort factors and
not a change in policy
No significant change
Kerr, D. et
al. (2018)
Kerr, W. C.
et al. (2017)
Kerr, W. C.
et al. (2018)
Prevalence rates in college students
Prevalence of adults
REC enactment in
Oregon
REC and MED enactment
and implementation
REC implementation in
Washington
Prevalence of adults aged 18 years
and over
4.3
Consumption patterns
The implementation of REC laws may affect cannabis consumption patterns in two important ways:
mode of administration and intensity of use. Commercial REC provision in the US allows promotion,
product innovation and price competition. Each of these factors is expected to shape the way
individuals consume the drug — how, where, when and how much. Product innovation allows the
substance to be consumed in edibles or vaporised through the use of an electronic cigarette.
Improved cultivation methods are shaping the potency of cannabis sold in REC markets, resulting in
consumption of higher THC levels and with variations in cannabinoid profiles. The rate and amount of
THC that regular users consume is likely to be shaped by changes in price and availability made
possible by commercial REC markets.
Nationally, the average number of days of use in the past month reported by past-month users
increased from 12.4 to 14.5 between 2003 and 2017 (SAMHSA, 2018). Figure 4.2 displays the
percentage of past-month users who reported daily or near-daily use (i.e. > 20 use days in the past
month) by state and for the entire country. For the entire country, the rate increased from 33.4 % to
41.7 % between 2003 and 2017. State estimates of daily or near-daily use have not been tabulated
beyond 2014, but a similar increasing trend is reported for most states. In 2014, approximately half of
past-month users in Colorado and Oregon reported using cannabis on 20 or more days, up from 38 %
and 37 %, respectively, in 2009.
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FIGURE 4.2
Past-month cannabis users aged 12 years and over using on a daily or near-daily basis (%)
60
50
40
30
20
10
0
2003
2004
2005
Alaska
2006
2007
Colorado
2008
2009
DC
2010
2011
2012
2013
2014
2015
US
2016
Oregon
Washington
Source: NSDUH
The previously mentioned study by Everson et al. (2019) which exploited variation in recreational
store density in Washington state not only found that those who lived within 0.8 miles (1.3 km) of a
store were more likely to report use in the past month, they also found that these individuals were
much more likely to report daily or near-daily cannabis use.
In addition to using individual-level NSDUH data to examine the association of REC enactment with
prevalence of cannabis use, Cerdá et al. (2019) also examined the association with frequency of past-
month use and past-year cannabis-use disorder (CUD). With respect to frequency of use, they only
found a statistically significant increase associated with those aged 26 and older. As for CUD, there
appears to be a small and statistically significant increase for youth, but the authors cautioned that
they could not rule out that unmeasured time-varying confounders may explain this finding (
13
). But for
those aged 26 and over, they report a statistically significant increase in past-year CUD and that there
was less concern that unobserved confounding may explain the association.
4.4
Product differentiation and price
As mentioned in the previous section, commercial REC has brought with it product innovation. Such
product differentiation and promotion, in turn, shape user behaviour and consumption. Cannabis
flower is still the dominant form of cannabis consumed in REC markets, but trends in data collected as
part of the seed-to-sale traceability systems in REC states suggest that new products that allow for
various modes of administration (vaporising, edibles and topicals) account for an increasing
proportion of sales. In one analysis of market trends in Washington, researchers analysed all
recorded retail sales (36 million observations) for a little more than two years (July 2014 to September
2016) (Smart et al., 2017). Researchers found that there were important changes in product type,
potency and price. Figure 4.3 is an updated reproduction from Smart et al. (2017), showing the
( ) Specifically, Cerdá et al. (2019) note: ‘E-value analyses suggested that unmeasured time-varying confounders
hypothetically more prevalent in [REC]states that increase the risk of cannabis use slightly (1.08-1.11 times) may explain this
finding. The extent to which such confounders exist is unclear because our difference-in-difference design accounted for
unmeasured time-invariant sources of confounding and also adjusted for measured time-varying individual- and state-level
demographic characteristics. However, the small E-values warrant a conservative interpretation of the increase in CUD among
participants aged 12 to 17 years.’
13
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FIGURE 4.3
Washington’s cannabis sales by product type after 37 % excise tax (million USD)
Source: RAND analysis updating Smart et al. (2017)
increasing trend in sales of edibles and vaporisable products, which grew to roughly one third of total
sales expenditures by mid-2017.
In terms of potency, an analysis of transaction data (included in the article but not shown here) shows
that the reported potency of cannabis flower, as measured by state-accredited laboratories, has
increased. The proportion of strains with reported THC concentration greater than 15 % grew to 93 %
by September 2016; cannabis flower of less than 10 % THC potency accounted for less than 2 % of
expenditures. The authors noted that cannabis flower with more than 20 % reported THC has
increased by almost half since October 2014, accounting for 57 % of the retail expenditures (Smart et
al., 2017) (
14
). As for price, it is hard to know what consumers would have faced in the absence of
REC legalisation but, as predicted, prices are falling. Updated analyses of Smart et al. (2017) and by
Davenport (unpublished) show that the average post-tax price for 1 g of cannabis flower fell from
roughly USD 20 in October 2014 to USD 10 in October 2015 and USD 7 in October 2017, and it
continues to decline (
15
).
A smaller study of MED and REC cannabis users from Washington and Colorado (n = 317) and a
web-scraping analysis of prices listed on Weedmaps (n = 3 802) compared user-reported and
dispensary-advertised prices of cannabis in both states during REC enactment periods with prices
after implementation (wave 1, October 2013; wave 2, May 2014; wave 3, October 2014). The authors
found that there was little price variation in the initial months post REC implementation but that
individuals reported paying higher prices for in-store purchases than for social purchases (Hunt and
Pacula, 2017). However, the authors noted that a limitation of the study is the very short time period
post REC implementation (within five months of stores opening). As noted above, other researchers
(Hansen et al., 2017a; Smart et al., 2017; Orens et al., 2018) have shown that prices do decline over
( ) We note that the potency reported by retailers may not be accurate. For example, initial studies of results from laboratories
in Washington show that there are clear systematic differences in potency results across laboratories but that general potency
results are inflated (Jikomes and Zoorob, 2018). State regulators have made efforts to address reporting biases.
( ) Price drops have also been documented in Colorado. A new study by Orens et al. (2018) reports that, from 2014 to 2017,
‘the price of one gram of adult use flower exhibited a steady downward trend, decreasing 62.0 percent, from $14.05 to $5.34
per gram’ (pre-tax).
15
14
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long periods of time, providing a strong indication that the immediate effects of these policies may be
different from outcomes in the longer term.
Our literature review did find two studies examining the promotion of REC cannabis products, but
these were excluded from further analysis, as they did not evaluate trends before and after REC
implementation.
4.5
Treatment admissions
It is hypothesised that commercial REC legalisation will change the intensity and frequency with which
individuals consume cannabis. This includes consuming cannabis more frequently as well as
consuming products with a higher potency. These factors may lead to cannabis use disorder and thus
increase the number of treatment admissions. However, it may take years for a cannabis use disorder
to develop, suggesting that any immediate changes in admissions may reflect the impacts not of REC
legalisation, but perhaps of MED use. At the same time, cannabis possession and use are no longer
criminal offences once REC laws have been adopted. Therefore, we would expect reductions in
criminal justice referrals to treatment for cannabis after the adoption of REC. A more general point is
that treatment admissions data are also influenced by the availability and perceived attractiveness of
services and reporting and diagnostic practices, all of which can vary over time. However, no studies
investigating changes in treatment admissions were identified during our review.
4.6
Adverse medical events
Under the assumption that REC legalisation increases consumption, a proportion of this type of
cannabis use may result in an adverse event (e.g. an overdose that results in an emergency
department (ED) visit or hospitalisation) (
16
). Accidental ingestions or overdoses, especially by young
children, may result from the supply of certain products, such as edibles that look like traditional
sweets. Regulators in Colorado and Washington promulgated emergency regulations to improve
labelling and warnings as well as educate the public about the potential effects of new products, some
of which are meant to look like benign consumables.
We identified eight articles that looked at changes in various adverse events (such as hospitalisations
or ED episodes) before and after (pre and post) MED/REC and their relationship with MED/REC
legislation. All articles examine outcomes in Colorado over various periods, some including MED
treatment periods. All were pre/post studies without any comparison groups, and may be subject to
self-reporting biases (e.g. individuals may be more likely to report cannabis use or seek medical
attention post REC). Therefore, caution should be exercised when interpreting their findings.
Significant differences were assessed using standard non-parametric hypothesis testing for all
studies. Two of the eight studies examined paediatric or child exposures to cannabis. All of them
examined hospital data assessing the impact of changes to Colorado’s MED and REC laws. These
studies report an increased frequency of adverse events post REC enactment or implementation, and
some have observed an increase prior to the adoption of REC, attributing this to lenient MED policies.
However, several studies compare different pre and post periods, which in some cases are not
immediately before or after the adoption of REC (comparing, for example, per capita rates of events in
2009 and in 2015).
Two studies compared paediatric cannabis exposures necessitating medical attention in Colorado
before and after MED or REC implementation. Both studies found statistically significant increases in
the frequency of such events following changes in legislation. Wang et al. (2016) report that the rate
of cannabis-related visits to the children’s hospital increased from 1.2 per 100 000 residents 2 years
prior to REC implementation (2012/2013) to 2.3 per 100 000 residents 2 years after (2014/2015)
( ) An ED visit is recorded when an individual presents to a hospital for emergency care but is not admitted for observation or
treatment. A hospitalisation is recorded when a patient is admitted for observation and treatment.
16
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(p = 0.02). The same study found a fivefold increase in annual poison control (
17
) paediatric cases for
cannabis exposures (from nine in 2009 to 47 in 2015) post REC implementation (
18
). This amounted
to an average annual increase in calls to Colorado poison control centres for cannabis of 34 %,
significantly more than the national average of 19 % (p < 0.001). In another retrospective study of
cannabis-related ED visits, Wang et al. (2018) found that cannabis-related ED visits increased from
1.8 per 1 000 in 2009 to 4.9 per 1 000 in 2015 (p
 = 
< 0.0001). Though rates increased, it is hard to
say what policy mechanism led to their increase. Cannabis policy in Colorado went through several
transformations between 2009 and 2015, including the adoption of several laws and voter initiatives
that formalised commercial markets.
Kim and Monte (2016) examined hospitalisation incidents coded for cannabis exposure between 2001
and 2014, collected by the Colorado Hospital Association, to compare before and after MED and REC
implementation. The authors found that cannabis-related hospitalisations doubled from 15 per
100 000 between 2001 and 2009 (the pre-MED commercialisation period, when dispensaries were
operating) to 28 per 100 000 between 2010 and 2013 (the post-MED commercialisation period)
(p < 0.001) (Kim and Monte, 2016). The authors noted that this statistically significant doubling
occurred after MED implementation. They then examined rates of cannabis-related ED visits between
pre- and post-REC implementation, reporting that the figure nearly doubled from 22 per 100 000
(2010-13) to 38 per 100 000 (January-June 2014) (p < 0.001).
Using a shorter time period, Kim et al. (2016) examined ED visits for cannabis from 2011 to 2014. The
authors reported no significant change from 2011 to 2012 in the rate of ED visits with ICD-9 codes of
cannabis use among out-of-state residents, which is possible given that MED is restricted to in-state
residents. However, from 2012 to 2014, the state-wide rate among out-of-state residents rose from 78
per 10 000 visits in 2012 to 112 per 10 000 visits in 2013 and 163 per 10 000 visits in 2014 (p < 0.001
for all comparisons). Among Colorado residents, the rate of ED visits possibly related to cannabis use
per 10 000 visits increased from 61 in 2011 to 101 in 2014 (p < 0.001) (Kim et al., 2016). By
comparing year-on-year changes, the authors sought to determine the association with changes in
REC enactment and implementation. ED data suggest that the rate of adverse events continued to
rise over the period, starting in 2011, perhaps because of the expansion of commercial medical
markets.
One study looked at annual rates of hospitalisations, ED events and calls to Colorado’s poison control
centres between 2000 and January to September 2015. Wang et al. (2017) reported that cannabis-
related hospitalisations increased from 274 to 593 per 100 000. Examining trends over time, Wang et
al. (2017) found a year-on-year increase in cannabis-related hospitalisations over a period starting in
2009 and ending in September 2015. The rates of ED visits also increased year on year, starting in
2011 (the first year for which data were available). The rates of ED visits significantly increased from
2012 to 2013 (358 v 443 per 100 000;
p
= 0.003) and from 2013 to 2014 (443 v 554 per 100 000;
p
= 0.0005). The prevalence of mental illness diagnoses in cannabis-related ED visits was five times
higher than the prevalence among those whose ED visits were not cannabis-related, and the
equivalent figures for hospitalisations showed a ninefold higher prevalence of mental illness
diagnoses among hospitalisations that were cannabis-related. Calls to poison control centres,
although flat between 2000 and 2009, increased significantly, from 44 to 93 in 2010 (p < 0.0001), and
again jumped from 123 to 221 (p < 0.0001) between 2014 and 2015 (Wang et al., 2017). The sharp
and sustained increase in adverse events began right around the time when MED commercial
dispensaries were formalised (around 2010) and continued throughout the adoption and
implementation of REC in 2014.
( ) Calls to poison control centres can be made by patients, the general public or medical professionals. In the US, there are
about 2 million exposure calls per year, approximately a quarter of which come from a healthcare facility.
( ) As a point of reference, Colorado Poison Control reported over 25 000 exposures for those under the age of 19 years
between July 2015 and June 2016.
18
17
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ED visits for cannabis-related mental health diagnoses also increased in Colorado post REC. Similar
to Wang et al. (2017), K. E. Hall et al. (2018) reported that, post REC implementation, the prevalence
of mental health diagnoses in cannabis-associated ED visits was five times greater than the
prevalence in ED visits not related to cannabis (prevalence ratio 5.35, 95 % confidence interval (CI)
5.27 to 5.43). The rate of ED visits in Colorado associated with both cannabis and mental health
significantly increased from 224.5 per 100 000 in 2012 to 268.4 per 100 000 in 2014 (p < 0.0001)
(Hall, K. E. et al., 2018).
In an analysis of ED events in Denver between 2012 and 2015, Sokoya et al. (2018) reported that the
number of maxillary and skull base fractures increased post REC implementation (2012-13 v 2014-15)
(p < 0.001 for both outcomes); however, counts of other facial/cranial fractures were unchanged. Bell
et al. (2015) examined cases of burns related to hydrocarbon exposure likely to be related to the
home production of butane hash oil extractions from January 2008 to August 2014, before and after
Colorado implemented its MED and REClaws. The authors reported no cases prior to MED
implementation, 19 cases between October 2009 and December 2013 and 12 cases in 2014, after
REC implementation (Bell et al., 2015). Although not reported, the average monthly rate increases
from zero in the pre-MED period to 0.37 during MED implementation and to 1.75 per month during
REC implementation. Unlicensed extractions using an ‘inherently hazardous substance’ were
subsequently criminalised in Colorado.
Though studies report increases in adverse events, it is possible that some increases could be due to
changes in reporting or measurement. For example, it is unclear if increases in ED visits and
hospitalisations are due to a greater willingness on the part of individuals to report use of cannabis
and/or if doctors are more aware of acute cannabis intoxication post REC and are now more likely to
screen for or confirm cannabis use using urinalysis.
4.7
Impaired driving
Changes in cannabis policy may affect impaired driving outcomes (such as accidents or citations for
driving under the influence) in multiple ways. While the bulk of the research suggests that driving
while under the influence of alcohol is more dangerous than driving under the influence of cannabis, it
also suggests that driving under the influence of cannabis is more dangerous than driving sober
(Caulkins et al., 2016). It is possible that impaired driving outcomes may change after the
implementation of REC, depending on whether cannabis becomes a substitute for or complements
alcohol consumption; however, there is mixed evidence as to the relationship. In our review, we
identified two studies that evaluated motor vehicle fatalities and one that examined reported insurance
claims.
One peer-reviewed study examined the impact of REC on motor vehicle crash fatalities in Washington
and Colorado and neighbouring states that did not pass REC but were substantially similar in terms of
traffic and roadway characteristics from 2009 to 2015. Researchers analysed changes in the annual
number of vehicle fatalities reported in the Fatality Analysis Reporting System (FARS), using a
standard difference-in-difference approach with random effects. They then compared four years of
pre-REC adoption (2009-12) outcomes with three years of post-REC enactment and implementation
outcomes (2013-15). The analysis found no statistically significant difference in fatal crashes between
REC and non-REC states (+0.2 fatalities/billion vehicle miles travelled; 95 % CI
−0.4
to +0.9)
(Aydelotte et al., 2017). However, the authors noted that their policy specification conflates REC
enactment and REC cannabis commercialisation, as they used the date the REC law was passed, not
the date when stores opened.
A National Bureau of Economic Research working paper (Hansen et al., 2018) employing synthetic
controls also assessed the impact of REC on motor vehicle crash fatalities in Washington and
Colorado and all states that did not adopt a REC law between 2000 and 2016. The authors found
that, between 2013 (the last year before REC implementation) and 2016, drivers testing positive for
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THC (
19
) increased in Colorado and Washington by 92 % and 28 %, respectively. However, the
authors concluded the following: ‘We find the synthetic control groups saw similar changes in
marijuana-related, alcohol-related and overall traffic fatality rates despite not legalising recreational
marijuana’.
Two more recent studies find evidence of an increase in traffic fatalities after legalisation. In a follow-
up study, Aydelotte et al. (2019) added additional years from the FARS database, comparing monthly
crash data from 2007 to 2017 in Colorado and Washington, which passed REC laws in 2012, against
five other states with MED laws, and four that did not change any cannabis laws. The authors also
examined changes in rates after opening of stores in Washington and Colorado in 2014. Aydelotte
and colleagues reported that the fatal crash rate in Washington and Colorado increased by 1.2
crashes (p
=
0.087) per billion vehicle miles travelled after REC enactment, but that there was a
statistically significant and larger increase after opening of stores (an increase of 1.8 crashes per
billion vehicle miles;
p
= 0.02). The results are sensitive to stores opening, supporting evidence that
REC implementation, rather than mere passage, may correlate with outcomes.
In another quasi-experimental analysis, Lane and Hall (2019) examined monthly traffic fatalities
between 2009 and 2016 in Colorado, Washington and Oregon compared to nine neighbouring
jurisdictions that did not change cannabis laws. Authors specified the opening of dispensaries as the
treatment condition instead of REC passage or enactment. They found that store openings were
associated with an immediate increase in 1.08 traffic fatalities per million residents followed by a trend
reduction of 0.06 fatalities per month (both
p
< 0.001). There was a similar step-up increase and
declining trend in both treatment states (step: 0.90,
P
< 0.001; trend:
−0.05,
P
= 0.007) and
neighbouring jurisdictions (step: 1.15,
P
= 0.005; trend:
−0.06,
P
= 0.001). They concluded that:
The results suggest that legalizing the sale of cannabis for recreational use can lead to a
temporary increase in traffic fatalities in legalizing states that can spill over into neighbouring
jurisdictions.
In another widely cited report, published by the Highway Loss Data Institute, authors compared auto
insurance collision claim rates (not necessarily fatalities) in Colorado, Washington and Oregon with
those in neighbouring states (Nebraska, Utah, Wyoming, Montana, Idaho and Nevada) that did not
adopt REC, from January 2012 to October 2016. The analysis found that collision claim frequencies
increased significantly by a combined rate of 2.7 % after REC implementation (Highway Loss Data
Institute, 2017).
The mixed results reported in the earlier studies identified are likely to be due to the difference in
outcomes evaluated, the specification of the REC policy change or the analytic methods employed.
Aydelotte et al. (2017) and Hansen et al. (2018) examined motor vehicle crash fatalities but with
different exposure variables (the latter was REC implementation, the former REC enactment); the
report by the Highway Loss Data Institute (2017) examined insurance claim data and the relationship
with REC implementation. Neither of the motor vehicle fatality studies found a relationship between
the fatality rates and REC. However, the report examining insurance claims did find a significant and
positive relationship, but one that does not negate findings from other papers. It is possible that non-
fatal accidents increased over this period, even if fatal accidents did not.
In the more recent analyses reported here, Aydelotte et al. (2019) and Lane and Hall (2019) examine
the relationship with motor vehicle fatalities and the opening of REC dispensaries. Both studies found
a positive relationship between opening of stores and motor vehicle deaths. These findings suggest
that the appropriate policy change to consider in evaluations is opening of stores, when product
becomes commercially available, instead of mere changes in the law.
19
( ) However, testing positive for THC is not an appropriate measure for impairment, as THC metabolites may remain in the
system long after the subjective and objective effects of intoxication have abated (EMCDDA and CCSA, 2018).
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Another possible reason for the inconsistency is the difficulty in identifying impairment at the time of
an accident. Current methods reported in traffic fatality and insurance claims data are not sufficient to
identify, among drivers who may have consumed cannabis within a specified time period before the
accident, those who were actually impaired. Until such technology is developed and widely adopted in
current reporting transport databases, we may not be able to sufficiently identify effects from
observational data.
4.8
Consumption of other substances
The use of cannabis may substitute for or complement other psychoactive substances. There have
been studies examining the relationship between the use of cannabis and alcohol, tobacco or other
drugs; however, most of these studies have evaluated the relationship in users of illicit cannabis. REC
and MED legalisation may substantially change the relationship or cannabis users’ access to other
drugs. There are relatively few studies examining the effect of licit cannabis on the use of other
substances or associated behaviours. Several studies have examined the population-level outcomes
associated with access to medical cannabis. It is important to consider the changes that REC may
have on the use of other substances. Social norms and commercial promotion of cannabis may make
the use of this drug more appealing to individuals who would have otherwise consumed alcohol in a
social setting. Likewise, there is an ongoing discussion in the US on using cannabis as a substitute for
riskier opioid analgesics to treat chronic pain (Hall, W. et al., 2018).
Several studies that examined the relationship with cannabis and other drugs are discussed in the
table in the Appendix. Yet an extensive and recently published review of this literature by Smart and
Pacula (2019) found complex and inconclusive results depending on the substance evaluated and
measure used. They concluded:
Evidence of the impact of cannabis liberalization on the use of other substances is
inconclusive. We have limited evidence of how alcohol or tobacco use has been impacted,
and despite a broader literature evaluating the impact of cannabis laws on opioid-related
outcomes, the findings from this literature are puzzling. Studies assessing impacts on self-
reported misuse and distribution of opioids show no impact of [MED laws], yet studies
evaluating opioid-related adverse events and opioid prescribing show reductions. Opioid-
related mortality, which early studies suggested was reduced by [MED laws], now appears to
be positively correlated with these policies and the adoption of [REC laws]. The significant
policy action being taken to combat the opioid crisis as well as the evolution of the types of
opioids driving opioid-related harm likely contributes to the lack of robust findings for this
outcome.
4.9
Criminal justice and public nuisance outcomes
The implementation of REC is likely to affect criminal justice and other public nuisance outcomes in
multiple and divergent ways. There are concerns about drug-induced crime and disorder, such as
acquisitive crime, vagrancy and public consumption. Likewise, REC may alter the broader systemic
elements associated with crime, including illicit trade and violence. For example, REC legalisation
could potentially lead some illicit distributors to other forms of crime, and unregulated processing that
causes explosions pose a public safety hazard; however, we are not aware of any studies examining
this. For some of these concerns, it is more than likely that the effects are mixed. For example, police
are no longer tasked with enforcing laws prohibiting the possession of cannabis but are now required
to stop and detain cannabis-impaired drivers. Some of these criminal justice outcomes are specific to
the policy choices found in the US. For example, under federal prohibition, cannabis businesses
cannot access the banking system and must deal almost exclusively in cash, making them a target for
robberies.
However, there are limits to interpreting law enforcement data. Reports may not be complete or
reflective of the change in outcomes. They also may be confounded by changes in policy directives or
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attitudes of individual officers. Post REC, public consumption may become more prevalent but under-
enforced as the public and law enforcement feel less compelled to intervene in minor infractions. As a
result, evaluating counts of public consumption citations may not reflect the true magnitude of
violations of the law with regard to using cannabis in public. Many other common ‘quality of life’
policing tasks are under-enforced. Cities have laws against littering, but these are often arbitrarily
enforced by police officers, as this is sometimes seen as a poor use of police time. Likewise, changes
in the estimates of intoxicated motorists may be a result not of REC per se but of changes in law
enforcement directives and training aimed at detecting impaired driving.
The studies evaluated here report mixed findings. Some suggest that REC is associated with
increases in some crimes but unrelated to changes regarding other crimes. This largely depends on
the stage at which the policy is evaluated (enactment v implementation) and where. Several studies
found that REC is associated with increases in cannabis-specific crimes (e.g. possession, sales) in
neighbouring non-REC states, suggesting that individuals may be moving cannabis over state lines.
Using Denver police data on crime reported by census tract, one study compared rates of violent,
property and cannabis-related crimes (defined as public consumption, robbery of a cannabis facility,
unauthorised distribution, etc.) during MED/REC in Colorado (from January 2013 to October 2015)
and examined whether or not they were related to the density of cannabis outlets. Freisthler et al.
(2017) reported that the density of cannabis outlets was not associated with property or violent crimes
in local areas, but the density of outlets was positively correlated with property crime in spatially
adjacent areas over time. Likewise, the density of outlets was associated with higher rates of reported
cannabis-specific crime in the same and neighbouring census tract (Freisthler et al., 2017).
Nevertheless, this analysis was not able to assess the relationship between unregistered caregiver
growers or home growers and incidents of crime. Furthermore, without an interrupted time series and
in the absence of controls, authors can only report a correlation with crime and dispensary density. It
is also possible that changes in law enforcement capacity and training may have confounded the
analysis.
At a more aggregated level, an interrupted time series study examined violent and property crime
clearance rates (i.e. rates in which a charge was made for a reported crime) each month from the
Federal Bureau of Investigation’s (FBI’s) uniform crime report data for Colorado and Washington,
compared with the US as a whole, from 2010 to 2015. Makin et al. (2018) estimate that REC
enactment in Colorado and Washington is associated with increases in police clearance rates for both
property and violent crime. This is the appropriate policy indicator, as criminal penalties for
possession and use were removed from the penal code on enactment. The authors employ an
autoregressive integrated moving average (ARIMA) model to control for seasonality effects in
robustness checks, reporting that their findings hold. Without measuring the mechanism of action
precisely, they attribute REC enactment to potentially increasing clearance rates by shifting
enforcement priorities in the field.
One working paper compared FBI arrest data from the uniform crime report in counties in Washington
and Colorado with those in neighbouring states from 2009 to 2014. The authors looked at arrests for
driving under the influence (DUIs) and various drug-related offences in relation to REC enactment and
implementation (2009-12 v 2013-14). They found that counties bordering Colorado saw an increase of
about eight cannabis possession arrests per 100 000 compared with non-bordering counties post
REC enactment and implementation; this was greater for counties bordering Washington, which saw
an increase of 22.9 arrests per 100 000 compared with non-bordering counties (Hao and Cowan,
2017). Reported arrest rates diminish the further the county is from the state borders of Washington or
Colorado, suggesting that cross-state diversion is occurring. However, law enforcement agencies
near the border may have shifted enforcement priorities (e.g. targeting out-of-state motorists),
potentially confounding such an analysis.
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When examining arrests for other drug-related offences (possession of other narcotics, distribution of
cannabis or DUIs), the authors reported no association between counties bordering a REC jurisdiction
and non-bordering counties post REC enactment and implementation. Nevertheless, the study
conflates the REC periods of enactment and implementation. It is more likely that cross-state
diversion would have occurred during the implementation period, after stores were opened than
immediately following enactment. However, their findings show mixed results. Rates of cannabis
possession arrests in counties bordering Colorado increased just prior to enactment in 2012, declined
in 2013 and increased again during implementation in 2014. In Washington, arrest rates in
neighbouring counties declined prior to enactment in 2012, increased in 2013 and then declined
during the first year of implementation in 2014. Such divergence could be explained by the fact that
jurisdictions neighbouring Washington have greater access to cannabis, with Oregon adopting a REC
law in 2014.
Another working paper examined Washington state recreational cannabis transaction retail data to
assess potential interstate trafficking between Washington and Oregon (Hansen et al., 2017b).
Washington implemented its REC in July 2014, whereas in neighbouring Oregon stores did not offer
recreational cannabis to adults until October 2015. Hansen et al. assessed the impact that REC
implementation in Oregon had on sales of cannabis on the Washington side of the border. They also
reported that retail sales near the border in Washington declined by 41 % immediately after REC
implementation in Oregon (Hansen et al., 2017b). The authors suggest that a substantial amount of
demand for cannabis in Washington may have originated in Oregon, resulting in considerable
interstate trafficking prior to REC implementation in that state.
4.10
Tax revenues
No studies have evaluated changes in cannabis policy and its impact on
overall
tax revenues (not just
those that are associated with cannabis excise taxes and fees); however, state regulators regularly
report sales and revenue data post REC. In Table 4.3, we report annual sales revenue and tax
receipts. Colorado’s figures are for the calendar year (CY) and Washington’s are for the fiscal year
(FY), which runs from July to June (2016 = July 2015 to June 2016). Retail cannabis sales surpassed
a billion dollars in Colorado in 2016 and in Washington in 2017. Sales and tax receipts have
increased year on year (with the exception of 2018, for which the information is partial).
TABLE 4.3
Cannabis sales and tax revenue
Colorado
Year
2014
2015
2016
2017
2018
2019*
Sales (CY)
(million USD)
683.5
995.6
1,307.2
1,507.7
1,545.7
386.7
Tax receipts (CY)
(million USD)
67.6
130.4
193.6
247.4
266.5
63.5
Sales (FY)
(million USD)
0
259.5
786.4
1,371.9
Not reported
Not reported
Washington**
Tax receipts (FY)
(million USD)
0
64.9
185.7
314.8
362.0
Not reported
*January to March for Colorado.
**Recreational only.
Sources: Colorado Department of Revenue, ‘Marijuana tax data’; Washington State Liquor and Cannabis
Board, Marijuana Dashboard reports sales and tax receipts throughout 2017; Washington State Liquor
and Cannabis Board annual report FY 2018 reports total tax receipts for that year.
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4.11
Public opinion
Our search found several studies that evaluated public opinion of REC. However, none of them met
our inclusion criteria, because they were point-in-time estimates, they failed to include pre-REC
measures or they were non-representative. That said, the longest running nationally representative
survey asking Americans if they think the ‘use of marijuana should be made legal’ has shown a
steady rise in positive responses since the mid-1990s. In 1996, one out of four Americans supported
making the use of cannabis legal. By 2012, support had hit 50 %, and this rose further, to 66 %, in
October 2018 (McCarthy, 2018). However, the poll asks about ‘use’, giving less indication as to
respondents’ opinions on commercial legalisation. Nonetheless, most commercial legal REC models
have been a result of popular voter initiatives.
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5.
Issues to consider when establishing a comprehensive
monitoring and evaluation framework for changes to cannabis
regulations
As discussions about cannabis policy intensify (Hughes et al., 2017), policymakers are in a unique
position to learn from the experiences of cannabis reform in the Americas. Doing so, of course,
requires an understanding of the motives or goals for the policy changes that occurred in that region
and the extent to which the policy changes have in fact achieved their stated goals. However, such an
understanding can only be achieved through actual measurement of the outcomes associated with
these stated goals of the policy reform, both before and after implementation. States in the US that
are adopting recreational cannabis laws often argue that such reforms will improve civil liberties and
generate tax revenues (Hall and Kozlowski, 2018). There is less emphasis placed on public health
and safety goals in the US than in the national discussions in Uruguay and Canada. Researchers
note that many jurisdictions have not paid adequate attention to the measurement and monitoring of
critical outcomes that are relevant to understanding the impact that REC may have on public health
and safety. Without establishing a robust baseline measurement prior to the policy changes, it is
difficult to accurately determine the causal impact of such reforms (including unintended
consequences) or if they met their intended objectives.
This is perhaps the greatest lesson that policymakers can learn from the early assessments
conducted thus far — the need to consider, measure and monitor public health and safety objectives
associated with cannabis policy reform before policy changes are implemented. Doing so requires
considering all of the potential objectives of cannabis reform that a country may wish to achieve as
well as the possible unintended consequences of such changes. Only then is it possible to identify
metrics that can be used to assess changes and begin collecting baseline data. Moreover, as
discussed in Section 3, many models of cannabis reform are available, and the regulatory model
adopted will depend on the specific objectives of the policy change and will also influence the
baseline and follow-up data that will be appropriate to assess if the objectives have been achieved.
This section offers insights into creating such a comprehensive framework. We begin with a taxonomy
of potential objectives that jurisdictions might seek to achieve (or harms to avoid) with cannabis
reform, mapping them to specific outcomes that can be used as metrics for monitoring and evaluation.
Since many of these measures are not currently collected, Section 5.2 offers some ideas for creating
a data infrastructure to collect them. Section 5.3 offers insights into evaluating changes.
5.1
Potential objectives of cannabis policy change and metrics of evaluation
Discussions of cannabis policy change should begin with a clear understanding of objectives.
Table 5.1 provides a taxonomy of potential policy objectives mentioned in jurisdictions that have
recently reformed cannabis laws. These are based on communications with policymakers as well as
statements made by proponents of ballot initiatives in US states that have recently voted on such
initiatives. The stated objectives are to reduce crime and improve civil liberties, to promote public
health and to generate economic activity and tax revenues. While not exhaustive, the examples
provided in Table 5.1 provide a sense of what might motivate a jurisdiction to reform its cannabis laws
and give us the opportunity to consider metrics for measuring the outcome of such a policy change.
However, it should be noted that, as illustrated above, the evidence of whether or not these regulatory
changes can achieve these outcomes is not yet available.
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TABLE 5.1
Statements commonly made by proponents of cannabis law reform
Crime/public safety and civil
liberties
Reduce/eliminate the illicit market and related crime
Re-prioritise law enforcement resources
Reduce burden on criminal justice system
Reduce criminalisation of non-violent drug offenders
Reduce racial or ethnic disparities; correct for injustices of drug prohibition
Health
Make cannabis-based products available for medicinal purposes
Allow for more research on medicinal benefits
Reduce youth access and consumption
Minimise contaminants and ensure product quality
Offer more information to users on potency and harms
Improve precision in dosing and potency
Make it easier to talk about cannabis-related problems
Reduce use of other potentially more dangerous products (alcohol, opioids)
Prevention
Economic/budget
Limit availability by regulating licensees and store operations
Increase government revenue through taxation and licensing fees
Reduce cost of prohibition on criminal justice system
Create new jobs in the legal economy (eliminate illicit market jobs)
Normative
Government should not control what someone puts in their own body
Prohibition lacks legitimacy
Similarly, a comprehensive evaluation of any policy change must consider the possibility of undesired
outcomes. In Table 5.2, we offer a list of statements commonly made by opponents of relaxing
cannabis laws.
TABLE 5.2
Statements commonly made by opponents of cannabis law reform
Crime/public safety
Will not decrease, and may possibly increase, illicit market activity
Burden on law enforcement and public safety
Increase drug-induced crime, accidents, and negligence
Increase in drugged driving
Health
Increase prevalence
Increase potency, reduce price, and increase access to new products
Entices youth and new consumers
Increases addiction and substance use disorder
Encourages experimentation and use of other drugs
Normalises drug use, potentially re-normalisation of tobacco use
Prevention
Economic/budget
Makes prevention campaigns ineffective
Increases costs to state
Reduces productivity
Normative
Sends the wrong message
Incompatible with international treaties
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Table 5.3 lists some potential metrics that could be used for monitoring and evaluating the impacts of
cannabis legalisation on particular policy objectives. This list is based on the studies listed in
Section 4 as well as our own experiences evaluating other cannabis policy changes. It also builds on
some of the suggestions offered in Kilmer and Pacula (2017). In the table, we have placed these
items into four general categories that are not mutually exclusive (
20
): health, crime and criminal
justice, economics and other. We are not aware of any country that collects all the variables listed in
the table, and it is likely that additional variables of importance are missing.
TABLE 5.3
Variables for monitoring implementation and evaluating changes in cannabis policy
Variables
HEALTH
Prevalence
General population surveys (GPS),
school surveys, medical surveys
Adult annual and 30-day prevalence rates are expected to
increase with cannabis liberalisation; however, the health
implications of this are unclear, as simple increases in
prevalence rates indicate nothing about the potential health
risks associated with consumption. More information about
frequency of use, mode of administration and product
consumed is needed to fully understand the potential health
impacts of the changes in prevalence rates.
The effect of legalisation on youth prevalence rates is
ambiguous. The rates could increase, as we expect they will
with adults, but they could decrease (1) if the regulated
market makes it harder for young people to access cannabis
and/or (2) if there is a forbidden fruit effect (MacCoun,
1993). These effects may also offset one another.
If cannabis liberalisation policies increase frequency of use
— especially daily/near-daily use — then there are greater
potential health effects. Specific health risks depend on the
demographics of the user group (young people v adults,
pregnant women or other at-risk users), the amount
consumed per dose, the potency and the cannabinoid
profile of the products consumed, and the method of
ingestion — all of which will influence the actual health risk.
The rates of CUD might rise or fall with cannabis
liberalisation, depending on what happens to heavy use and
treatment admissions.
On the one hand, a decrease in criminal justice referrals
could reduce the probability of someone with CUD receiving
treatment. On the other hand, legalisation may make it
easier for those with CUD to talk openly about their
problems and obtain help.
Sources for obtaining these data
Implications for evaluating policies
Frequency
GPS, school surveys, medical surveys
Cannabis use disorder
(CUD)
GPS or school surveys; voluntary
treatment, and ED and hospital
admissions; qualitative interviews with
selective populations — all of these
sources capture a subset (sometimes
overlapping) of people with CUD
For duration, longitudinal studies
would be strongly preferred, but it may
be possible to get some of this
information from retrospective
surveys.
GPS, school surveys, medical
surveys, traceability data and
qualitative surveys of key user groups
Products used
There are different risks associated with different types of
cannabis products. Some adverse health events are tied
directly to acute overconsumption of THC, while other
longer term health effects are related to the method of
administration (i.e. the long-term effects of smoke on the
respiratory system). As a result, information on the products
used will be useful for thinking about the potential health
consequences observable among the population.
( ) For example, traffic accidents could be included in either health or crime.
20
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Variables
Amount consumed
Sources for obtaining these data
Questions about the amount of
cannabis consumed may be included
in GPS or school surveys as well as
medical surveys. Some web-based
surveys ask about the amount
consumed and use picture prompts to
help guide respondents. In such
cases, respondents are randomly
shown a photo of different amounts of
cannabis and asked to quantify how
much they think each amount weighs.
This improves researchers’
understanding of the amount of
cannabis consumed. Capturing the
potency of the product (actual or
perceived) is also useful but may best
be obtained through qualitative
interviews with selective populations.
GPS, school surveys, medical
surveys; treatment admissions;
hospital and ED admissions; and
qualitative studies of key user groups
Implications for evaluating policies
The amount consumed per day or per episode of use is
important for understanding (1) the risk of an acute harm
and (2) the risk of developing a CUD. Ideally, it would be
preferable to move beyond grams of herbal cannabis or
puffs from a vape pen towards collecting information about
the consumption of THC and other chemicals in the
cannabis plant.
Prevalence and
consumption of other
substances
The net effects of cannabis liberalisation on public health
depend on whether cannabis becomes a substitute for or
complements other potentially harmful substances. For
example, if cannabis is used most often with tobacco (i.e.
they are ‘complements’), then cannabis legalisation might
hamper efforts to reduce tobacco use. If cannabis and
alcohol are substitutes, then having users switch from
alcohol to cannabis might generate net health gains (e.g.
reduced accidents, reduced domestic violence, reduced
liver cirrhosis). If cannabis and alcohol are complements,
then some health risks may be made worse with cannabis
liberalisation policies (e.g. accident risk, heart risk). Thus, it
is important to understand if liberalisation policies lead to the
use of cannabis in lieu of other substances (tobacco,
alcohol, opioids, new synthetic cannabinoid agonists) or to
joint consumption. This might differ among different
segments of the population.
Even if cannabis use does not directly cause mental health
disorders but simply increases the likelihood of onset at an
earlier age, cannabis liberalisation policies may still increase
the prevalence of some mental health disorders (psychoses,
schizophrenia, etc.). The correlation may depend on the
typical amount consumed, frequency of use and THC
exposure.
If cannabis liberalisation policies lead to an increase in
consumption such that they increase the prevalence of
CUD, it is possible that a jurisdiction will see a rise in
cannabis-related treatment admissions. However, if
treatment referrals for cannabis come largely through the
criminal justice system, then legalisation may lead to an
overall decline in treatment admissions.
ED visits and hospitalisations may emerge from one of three
potential mechanisms: (1) immediate unexpected reactions
to cannabis products consumed by naive users (e.g.
accidental poisoning from edibles); (2) risky modes of
consumption (e.g. dabbing) or behaviours while intoxicated
(e.g. driving); and (3) longer term health problems
aggravated by prolonged cannabis use, particularly in
certain forms of products (e.g. respiratory issues from
smoking).
Calls to poison control centres typically result from
overexposure to THC, which most frequently occurs through
the overconsumption of edibles (multiple standardised
doses) or exposure to high-potency products.
Other mental health
disorders
GPS, school surveys, medical
surveys; longitudinal surveys;
treatment admissions; hospital and ED
admissions; qualitative studies
involving key populations
Treatment admissions
Treatment facilities; healthcare
systems; GPS surveys; qualitative
studies on selective populations
Possibly from government healthcare
records
Hospitalisations and ED
visits
Hospital databases; insurance claims
Calls to poison control
centres
Poison control centres; emergency
service calls
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Variables
Education and
employment outcomes
Sources for obtaining these data
GPS or school surveys; longitudinal
surveys; education and employment
agencies; standardised testing results
in secondary schools or for
graduation; graduation rates;
employee drug testing data
Implications for evaluating policies
Absenteeism and presenteeism are both potentially affected
by increases in cannabis use, particularly if cannabis is
consumed prior to or during work or school. Such behaviour
could ultimately influence longer term productivity and tax
revenues of the government. Tracking changes in education
and employment outcomes before and after the adoption of
a change in cannabis policy can help identify the need for
additional workplace/school policies or targeted messaging
regarding appropriate use.
CRIME AND CRIMINAL JUSTICE
Cannabis-related arrests
and seizures
Police statistics
The legalisation of cannabis should generate a net decrease
in the number of arrests and seizures, but these will not fall
to zero for at least two reasons: (1) most jurisdictions retain
the prohibition of use/purchases by young people and (2)
illicit markets may persist for some time after a policy
change. Information on arrests can provide insights into
criminal justice savings associated with legalisation, while
seizure data can provide some insight into profit motives for
the illicit market to remain (e.g. specific products not
available in the legal market, or specific populations unable
to participate). Nevertheless, law enforcement data may be
biased because of internal policy directives and changes in
resources, agency capacity and citizen reports. Caution
should be used when evaluating these data.
Enforcing new regulations adopted by a jurisdiction around
legal cannabis will require resources, so tracking information
on cannabis-related police contacts (including those that
simply lead to confiscation) is important for accurately
understanding the net budgetary impacts on crime and
public safety resources. This information can also be useful
for understanding how changes in cannabis laws affect
racial/ethnic disparities in criminal justice outcomes.
Though some individuals may already be processing illicit
cannabis flower and turning it into concentrates, the
legalisation of cannabis might encourage more people to
extract cannabinoids from dried plant matter using volatile
chemicals and solvents. Unsafe processing practices may
pose a public safety hazard should the volatile chemicals
combust.
In the US, arguments have been made that cannabis
legalisation will improve civil liberties, reduce racial
disparities in the criminal justice system and improve police-
community relations. Monitoring how the criminal justice
system responds to changes in the law will allow us to
evaluate these arguments.
As previously stated, the enforcement of new regulations
adopted within a jurisdiction will require some criminal
justice resources, particularly if some violations of the new
regime still involve criminal penalties. Tracking this
information is necessary for understanding the cost of
enforcing the new policy and net criminal justice savings.
This is one of the most likely infractions to arise in response
to the legalisation of cannabis within a jurisdiction, although
the rate of increase depends on a variety of factors,
including a jurisdiction’s reliance on cars, the deterrent
effect from law enforcement and the effectiveness of
prevention campaigns to promote sober driving/responsible
use. However, not all impaired driving will be detected, so,
given limited policing resources, these data will be useful for
understanding which groups are likely to drive under the
influence of drugs and where and at what times such
behaviour is likely to occur.
Cannabis-related police-
citizen contacts
Perhaps police databases — new
record keeping may be required
After legalisation, civilians could also
track consumption in public spaces
Unregulated cannabis
processing involved in
explosions
Police or public safety statistics
Penalties for cannabis
offences
Court records; corrections agencies,
police databases
Criminal justice spending
on enforcing cannabis
laws
Police databases; court records;
corrections agencies; regulatory
agency data (compliance checks,
citations, fines)
Self-reported impaired
driving (or travelling with
someone who is
impaired)
GPS, school surveys, medical
surveys; could be added to treatment
intake surveys
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Variables
DUI prosecutions
Sources for obtaining these data
Police statistics; insurance claim data;
qualitative data collection in particular
areas
Implications for evaluating policies
DUI arrests and prosecutions are a function of (1) the
amount of impaired driving and (2) the level of enforcement.
Higher DUI arrests without additional enforcement suggest a
rise in impaired driving and the need for additional
messages to be targeted at at-risk users. It also raises the
criminal justice costs associated with legalisation. However,
total DUI arrests might fall with a change in policy if
cannabis becomes a substitute for alcohol. Thus,
information on DUI arrests (for alcohol, cannabis and other
substances if available) can help inform the jurisdiction
about how cannabis is being used by specific segments of
the population. Nevertheless, changes in enforcement
priorities and training may confound analyses that use law
enforcement data.
Changes in traffic crashes and fatalities may indicate a
change in impaired driving that is not reflected in arrest
statistics. Objective analyses will focus on the total number
of crashes/fatalities, not just those in which the driver tested
positive for THC. This can offer a better understanding
regarding the potential substitution of cannabis for alcohol or
their concurrent use.
Tracking changes in arrests/convictions for other crimes
helps to identify the public safety benefits/costs associated
with legalisation — in so far as arrests reflect changes in
crime patterns (that may be associated with use of cannabis
and/or its substitutes or complements). Nevertheless,
changes in enforcement priorities and training may
confound analyses that use law enforcement data.
Since not all crimes result in an arrest, tracking information
from calls to emergency services may identify changes in
the need for law enforcement intervention because of a
change in the consumption of cannabis and/or its
substitutes and complements.
Information on the changes in victimisation with the
legalisation of cannabis is relevant for considering public
safety impacts. Again, it is unclear if victimisation would rise
or decline with legalisation; much will depend on how the
policy change affects the use of other substances.
Traffic crashes or
fatalities
Transport and insurance claims
databases
Arrests/convictions for
other crimes
Police databases; court records
Calls to emergency
services
Police databases, possibly other
government agencies
Victimisation surveys
Victimisation surveys; medical reports
ECONOMICS
Total expenditures on
purchasing cannabis
products
GPS; retail sales (medical or other
outlets); combining consumption
estimates from wastewater testing with
THC price estimates
Information on cannabis expenditure serves at least three
purposes: (1) it helps identify tax evasion, particularly if
taxes are tied to the amount sold; (2) it is helpful for
understanding which products are sold (by form and
potency if information is collected by product); and (3) it is
useful for constructing an estimate of the total size of the
cannabis market (demand based), which can then be used
as a way of measuring the impact of further policy
refinements on the market.
Information on the source of cannabis is very helpful for
understanding the extent to which the legal market is able to
replace the illicit market.
Traceability systems are valuable for a range of regulatory
purposes in a legal cannabis market, including (1)
measuring the total amount supplied to a market (which,
when combined with a demand estimate, can identify the
presence and size of an illicit market); (2) projecting
estimates of tax revenue from sales (which can then be
compared with actual tax revenue to help identify tax
evasion); and (3) identifying and tracking products sold,
which is useful for understanding the potential health risks
that consumers might face (this is relevant to prevention
messaging as well as the issuing of product recalls).
Source of cannabis
supply
Amount of cannabis
produced in the legal
market
GPS; web surveys of heavy users
Traceability systems; visual
inspections
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Variables
Prices
Sources for obtaining these data
GPS, medical surveys, arrestee
surveys; web surveys of heavy users;
menu analyses; traceability systems;
law enforcement sources;
crowdsourcing websites such as ‘Price
of Weed’
Regulatory agency overseeing
cannabis legalisation; local
government zoning boards
Implications for evaluating policies
Prices are important, because they can influence many of
the outcomes that are discussed in cannabis policy debates:
size of the illicit market, tax receipts, business revenues and
consumption.
Presence of retail
establishments
The illicit market for cannabis can be reduced if there is a
licensing system identifying legitimate sellers from illegal
sellers. Enforcement against illegal sellers is a necessary
component of a licensed system. However, the density of
retail establishments can also influence the perceived
availability (changing norms about the substance) and can
reduce the effectiveness of prevention programmes aimed
at reducing use among particular groups. The regulation of
retail establishments will be a cost of legalisation, affecting
net revenues from a change in policy. More retail
establishments increase the number of entities that need to
be policed (and hence the cost of doing so).
Tracking sales and tax revenue is important for measuring
the size of the market and whether or not tax revenue is
growing. These taxes are often earmarked for prevention
efforts, regulatory oversight and other costs imposed by
users on society.
Information on employment in the cannabis industry can
indicate the economic value of the industry to a community.
It also provides insights into the relative importance of this
industry vis-à-vis other industries in an area.
Of course, legalisation can affect other segments of the
economy, besides those directly involved in the cannabis
trade.
While there are likely to be criminal justice savings
associated with cannabis legalisation, there are also agency
costs associated with regulating a new business. The
economic impact of legalisation is a function of the jobs and
tax revenue that comes with the new market minus the cost
of regulation and law enforcement monitoring and regulating
the new market. This information is vital for a proper
estimation of the net economic impact of legalisation.
Licit sales and tax
revenues
Regulatory agency overseeing
cannabis legalisation; other
government agencies
Employment in the
cannabis industry and
other related industries
Could try to deduce this from total
production estimates and qualitative
methods pre legalisation; after
legalisation, it should be part of regular
labour statistics
Cost of regulation and
law enforcement
Regulatory agencies overseeing
cannabis legalisation; police
databases; court records; corrections
OTHERS
Consumer characteristics
Administrative or regulatory data;
qualitative studies of key target
populations
Jurisdictions that collect information on patients or
registered adults (e.g. Uruguay) may allow for a further
understanding of the user base. This could include
descriptive information on patient ailments or demographic
information regarding a typical registrant and how much
they purchase over the course of a year.
These polls provide a source for evaluating the normative
justification for a change in cannabis policy.
The degree to which cannabis products are advertised and
promoted might influence the type and amount of prevention
material needed by a community to reduce the potential
harms associated with legalisation.
Public support
Advertising/promotion
Public opinion polls
Could require all cannabis
advertisements be reported to
regulatory agencies; could also
conduct studies by the European
Medicines Agency
5.2
Establishing the data infrastructure
Once a jurisdiction has identified the objectives for considering a policy change as well as specific
metrics that would be useful for monitoring impacts, it can then consider appropriate data collection.
The second column of Table 5.3 offers ideas for collecting or generating relevant data. Keep in mind
that there are strengths and weaknesses of different data sources and various approaches. In this
section, we discuss in greater detail some of the issues to consider when relying on some of these
sources.
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General population surveys (GPS) and student surveys
GPS and student surveys will be useful for some of these items, but care must be taken when using
these data to draw inferences about cannabis policy changes, for several reasons. Most importantly,
there is strong evidence suggesting that survey respondents under-report the prevalence of drug use
in GPS (e.g. Harrison et al., 2007). While many studies have relied on assumptions that under-
reporting — although unknown — is fairly stable year on year, these assumptions will not necessarily
hold if a policy changes. For example, if a policy change reduces the stigma around admitting
cannabis use, then more people will be willing to honestly report their prior behaviour, making it hard
to identify the extent to which any change detected is attributable to a true increase in cannabis use
as opposed to more honest reporting, or both.
One way to assess the degree to which under-reporting might exist and change with policy would be
to validate the GPS with a biological test (e.g. saliva tests or urinalysis), to determine the proportion of
respondents who are misreporting at a given point in time. This has been done in the US, but we are
not aware of any attempts to do this in Europe (Kilmer et al., 2015). Another alternative that might be
considered is to incorporate the use of the randomised response technique for key estimates into the
questionnaires (Blair et al., 2015). Such validation does not have to be done every year, but doing it
now and possibly a few years after a significant policy change would provide extremely useful
information about baseline rates of under-reporting and how these change over time. The use of
wastewater epidemiology may potentially generate useful confirmatory measures for cannabis
prevalence rates (Zuccato et al., 2008). Countries in Europe and elsewhere may not want to rely on
US under-reporting estimates from nearly 20 years ago to inform these adjustments.
There are also some questions that could be added to GPS regarding consumption and expenditure
that would improve our understanding of these markets and how they could change (e.g. asking about
the types of cannabis products used and the amount consumed). Adding questions about market
transactions is critical for understanding expenditures and revenues generated by illicit suppliers,
which is important if the goal is to understand the impact of policy changes on the size of the illicit
market. Since it may not be possible to add an entire cannabis market module, as was done in the US
from 2002 to 2014 (and reinstated in 2018), adding two questions concerning (1) the amount spent
during the last purchase and (2) the number of purchases in the previous month would be enough to
provide the foundation for market estimates.
It would also be helpful to collect information about the types of products purchased. Information on
the types of products is especially valuable if a jurisdiction decides to limit the legal sale of cannabis
to particular forms (e.g. herbal cannabis), which Uruguay does. Responses can indicate if individuals
are sourcing other products (e.g. edibles) from illicit markets.
Web surveys
While it is possible to use internet-based surveys with strong sampling frames to generate population-
representative inferences about cannabis use and purchasing patterns (e.g. Pacula et al., 2016),
many of the web surveys about cannabis fielded in Europe and the US are convenience samples (e.g.
Kilmer et al., 2013; van Laar et al., 2013; Matias et al., 2019). While these relatively inexpensive
surveys do not allow for precise estimates about a representative sample, they can provide plausible
ranges for key variables if the samples are large enough. If targeted correctly, they can help provide
information about heavy users, who may be less likely to be included in the sampling frame for GPS
or student surveys but account for the largest part of consumption and expenditures (Kilmer et al.,
2014).
Indeed, combining estimates from GPS and web surveys is becoming an increasingly popular
approach to generating market estimates for consumption and expenditures. Typically, the GPS
estimates of the number of use days are combined with the web survey estimates of the amount
consumed per use day for various types of users (e.g. weekly, daily/near daily). In some cases, these
estimates are generated only for an entire country (e.g. Caulkins and Kilmer, 2013), while other
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
studies generate these estimates for specific age or gender groups and then add them together to
generate an aggregate estimate (e.g. Caulkins et al., under review; van Laar et al., 2013). Another
approach to using unrepresentative web surveys to generate population-wide estimates is to use a
raking algorithm to reweight web survey respondents to match GPS data (see Caulkins et al., 2019).
Cannabis medical surveys
In the light of the changes happening within US jurisdictions, several health insurers are beginning to
elicit information about cannabis use (both medicinal and recreational) in their regular patient surveys
so as to monitor use of the substance in a fashion similar to alcohol and tobacco. While this
information is not publicly available from private insurers, it could easily be collected by public insurers
in various jurisdictions. Distinguishing medicinal consumption from recreational consumption would be
key, as the particular forms of cannabis, the amounts consumed and frequency of use are likely to
differ, depending on the subpopulation considered (Pacula et al., 2016; Lankenau et al., 2017).
Cannabis tracking systems
In the shadow of federal prohibition, states that passed legalisation have implemented ‘seed-to-sale’
traceability systems to signal that they are taking the issue of diversion seriously. These systems track
every plant throughout the supply chain, ending at retail sale. They can include information about the
prices paid by processors and retailers as well as information about cannabinoid content and the
types of products sold on the licit market. While these systems were not necessarily designed for
research purposes, they are being used by an increasing number of researchers to help understand
the markets and other cannabis-derived products (Smart et al., 2017), to estimate the price elasticity
of demand (Hansen et al., 2017) and the level of competition in the market at the wholesale and retail
levels (Caulkins et al., 2018).
In the US, there are no systems to track sales made to specific individuals (i.e. the identities of
purchasers is not tracked), but there are in Uruguay. In addition to a seed-to-sale system, Uruguay
tracks and limits purchases by individuals. Retail purchases can be made only at participating
pharmacies and are limited at 40 g/person/month. To make sure individuals do not exceed these
limits, a biometric system requires registered buyers to submit a thumbprint before making a purchase
(Miroff, 2017). The pharmacy receives immediate feedback from the government database about
whether or not the person has exceeded the allowable retail transaction limit; if not, the sale is made.
The total weights and numbers of sales per location are then reported to the national monitoring
agency.
Other countries considering changes in cannabis policy are not constrained in the same way as the
states in the US, and may want to limit the amount of cannabis that can be purchased in a given time
period, or consider implementing seed-to-sale systems to obtain data that are relevant to other policy
objectives, including identifying leakages to the illicit market, contaminated products for recalls and
valuable information regarding the types (and amount) of various products sold. This information can
be important for monitoring compliance and providing information for economic and other analyses.
Such information will allow regulators and researchers to triangulate with other indicators, such as
self-reported user behaviours from population surveys.
5.3
Thinking seriously about outcome evaluations
The third column of Table 5.3 provides an explanation for why particular types of data are useful for
generating inputs that can be used to measure many outcomes of interest, including (1) the actual
demand for cannabis in a market; (2) the size of the legal cannabis supply and industry; (3) the size of
the illicit market supply of cannabis; (4) the net impact of cannabis legalisation on the criminal justice
system (arrests), the public safety system (calls to emergency services, victimisation) and the health
system (hospitals, poison control centre calls, accidents); and (5) the net economic impact of the
market on the government in terms of jobs created, tax revenue, regulatory costs and health/law
enforcement net costs (or savings). It is worth mentioning that this report and many evaluations of
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
REC to date exclude any evaluation of the benefits — including mere pleasure — of legal cannabis
reforms. It is difficult to assess these consequences, as they are often subjective and difficult to
quantify, but any serious evaluation of these legal changes ought to consider these outcomes
(Caulkins et al., 2016).
Collecting the appropriate outcome data is necessary but insufficient for evaluating these policy
changes. Serious thought must be given to defining precisely what is evaluated and what is the
counterfactual, to allow the determination of causal inference about policy change. This section
addresses some of the issues for those considering an evaluation.
Understanding the cannabis market and expected sanction for a cannabis violation
before
the
policy change
There are a number of mechanisms that may influence cannabis use after a policy change, such as
stigma, price, promotion, availability, expected sanction and the ‘forbidden fruit’ effect (MacCoun,
1993). Collecting the baseline data for price and expected sanction is important for understanding not
only the casual mechanisms at play but also how different forms of legalisation may have different
effects on use and other outcomes. For example, if a jurisdiction that does not criminally sanction
cannabis possession chooses to legalise the supply of cannabis, the criminal justice cost savings of
doing so will not be as great as a jurisdiction that criminally sanctions cannabis users. Alternatively, if
a government implements a regulatory regime that keeps the price per unit of THC similar to its pre-
legalisation price, it may not detect as much of an effect on use compared with other regimes that
have experienced price declines as a result of market competition (Kilmer et al., 2010).
Collecting market information (e.g. information on prices, products, promotion, the number of outlets)
is important, especially for jurisdictions that had vibrant commercial medical markets before
recreational legalisation. It could also be useful in countries such as Spain, where, despite national
prohibition, significant numbers of cannabis social clubs are tolerated in some regions, some of which
may become increasingly commercialised (Pardal, 2018).
Canada has made an effort to obtain baseline data for future evaluations. For example, building on
the Canadian Student Tobacco, Alcohol and Drugs Survey, Health Canada designed the Canadian
Cannabis Survey, aimed at understanding the pre-legalisation cannabis market. In 2017, the national
government fielded the phone-initiated survey designed to obtain a sufficient representation among
key population groups across all provinces and territories. The survey not only included questions that
are relevant to cannabis consumption but asked respondents about their purchasing habits (how
much they bought, how often, from what sources and at what prices). The findings informed
discussions on the cannabis law and will also be used to evaluate its implementation in the future
(examining changes in prevalence, price, frequency of use, etc.). In addition, Public Safety Canada
commissioned work to estimate the price of cannabis throughout the country (Ouellet et al., 2017),
and Statistics Canada created a ‘Cannabis Stats Hub’, which has many similarities to the EMCDDA’s
Statistical Bulletin but includes more detailed information about the cannabis economy.
Considering the counterfactual and underlying context
Section 4 highlights the growing number of studies recreational legalisation in the US that include a
control group, but much attention is still paid to simple pre-post analyses of trend data (for more on
trends, see Appendix C). While cross-jurisdictional comparisons seem like an obvious approach to
applying rigorous research methods to learn about these policy changes, caution must be exercised,
as important differences in definitions, survey methodologies, the frequency of data collection and
other factors can limit inferences from these exercises (MacCoun, 1993; Kilmer et al., 2015;
Giommoni et al., 2017). More importantly, the assumption that any single jurisdiction adopts a uniform
policy, which is required and embedded in many cross-national studies, is clearly problematic (e.g.
states in the US vary considerably in terms of their cannabis regulations and enforcement). Similarly,
context matters. Different jurisdictions may have different starting points for the adoption of REC. This
may be less of a transition for a jurisdiction with a robust medical cannabis market or some social
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access (e.g. the Dutch coffee shops or cannabis social clubs in Spain) than for a jurisdiction that
aggressively enforces cannabis prohibition.
Another approach is to take advantage of within-state variation in how policy is being implemented.
For example, although the states of Colorado and Washington passed legalisation in 2012, there are
still a number of localities in these states that do not allow retail stores. This has allowed researchers
to exploit the variations in retail cannabis outlet density to learn more about the effect of
commercialisation (e.g. Dilley et al., 2017). Similarly, studies exploiting variations in medical cannabis
access within California have been carried out to examine the impacts on use, hospitalisation and
crime (e.g. Mair et al., 2015; Freisthler et al., 2016; Hunt et al., 2018). An advantage of using intra-
state variation is that there is less concern about data comparability and policy comparability, and
there may be shorter time lags. Of course, there may be important issues of policy endogeneity that
will need to be considered in the statistical models (Pacula and Smart, 2017).
Paying close attention to dates and isolating policy exposure
The date used to denote when the policy change occurred obviously has important implications for
the results of outcome analyses. There can be not only lags between the date of passage and the
date the policy goes into effect but also important lags between passage and the ability to purchase
cannabis from a store, as it can take time to build a regulatory system. For example, the voters in
Colorado and Washington passed legalisation in November 2012, but the recreational stores did not
open until January 2014 and July 2014, respectively (
21
). Thus, outcome analyses of legalisation that
use dates when laws were passed, rather than when stores opened (or when a majority of the adult
population had access to cannabis), are at serious risk of drawing the wrong conclusions if changes
are driven principally by market activity and not shifts in norms (Pacula and Smart, 2017). The dates
can also be useful for learning more about the causal mechanisms underlying possible changes in
use (e.g. the period when it is legal to use or possess but before the stores have opened) and
understanding the short- and long-term implications of these policies.
It is imperative that when regulatory changes are introduced, governments, or possibly agencies such
as the EMCDDA, document what the legal changes allow/require and whether or not local variation is
permitted (e.g. if shops allowed). Although this seems obvious, it can be difficult to obtain this
information, as enacted laws may not include regulatory details that can influence outcomes of
interest (e.g. testing requirements). Better-prepared jurisdictions will require regulatory agencies to
publicly document this information and note when changes are made to regulations. This type of
documentation is especially important if the new policy allows local variation.
Acknowledging that the short- and long-term effects of legalisation could be different
It is entirely possible that the short-term effects of a policy change differ from the long-term effects.
This is likely to be true, as knowledge about products and how they might be used (or misused) takes
time to develop, as do changes in social norms concerning the appropriate (or inappropriate) use of
the products. Even existing markets can see the introduction of new products (e.g. hash oils and
concentrates) that capture different properties of the original cannabis plant (e.g. higher THC content)
and which can also change the known health impacts of the substance. It is certainly the case that we
have very little knowledge of the health implications of the products currently sold in US legal markets
(e.g. Kilmer, 2018). Most of the research on the health benefits and consequences of cannabis are
based on cannabis plant material with far lower THC and higher CBD concentration levels than those
observed on the legal market in the US today. Thus, it is difficult to infer the long-term effects of these
newer, less researched, products.
( ) Even though some stores opened in Washington in July 2014, it was some time before most of the licensed stores opened
and had enough inventory to push prices below the pre-legalisation levels.
21
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6.
Concluding thoughts
This document is intended to inform discussions about the value of having tools in place to evaluate
the impact of any major changes to the regulatory approach to cannabis used. By highlighting the
various approaches unfolding in the Americas and some of the emerging evidence from states in the
US, namely Colorado and Washington, we construct an analytic framework and empirical foundation
that we hope will contribute to productive and dispassionate policy discussions.
We cannot stress enough that the peer-reviewed literature review on legalisation of adult cannabis
use is nascent, and that results are likely to be conflicting, depending on which data and methods are
used as well as which policies are evaluated. It is important to remain sceptical of early studies,
especially those that use a simple binary variable to classify legalisation and non-legalisation states.
This scepticism should extend to the many studies that fail to account for the existence of robust
commercial medical cannabis markets that predate recreational cannabis laws. Even if a consensus
develops on certain outcomes, this does not mean that that relationship will hold over time. Changes
in norms concerning cannabis use and potentially other substances, the maturation of markets and
the power of private businesses (if allowed) could lead to very different outcomes 15 or 25 years after
recreational cannabis laws have been passed. Evaluations of these changes must be considered an
ongoing exercise, not something that should happen in the short term.
Insights from evaluations of possible supply changes in Europe will depend on the number of data
collected before the change; simply comparing past-month prevalence rates will not tell us much
about the effect of the change on health. While US jurisdictions have been moving quickly to legalise
cannabis, the data infrastructure for evaluating these changes is limited. In contrast, Canada has
made important efforts to field new surveys and create new data collection programmes in
anticipation of legal changes. If
some
jurisdictions are considering a major adjustment to cannabis
supply policies in the near future, then it is prudent to start thinking as soon as possible about
improving data collection and analysis systems to support subsequent evaluation exercises. Given
the open borders that exist within the EU, the wider impact of policy changes made within any one
country will also deserve consideration. Section 5 of this report should serve as a useful resource for
some of these discussions.
While there is much to learn from what is happening in the Americas, policy discussions should not be
limited to approaches implemented there. There are several regulatory tools (e.g. minimum pricing,
potency-based taxes) that receive very little attention — if any — that could have important
consequences for health, public safety and/or social equity (
22
). Acknowledging that individuals (and
governments) have different values and preferences for risk when it comes to cannabis policy can
make for more productive discussions on this controversial topic.
( ) Uruguay is one exception here. The government does not set a minimum price for cannabis sold in the pharmacies — it
sets the price. Some provinces in Canada are contemplating THC potency taxes, while others have the authority to set a price
floor.
22
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TECHNICAL REPORT
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
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TECHNICAL REPORT
I
Monitoring and evaluating changes in cannabis policies: insights from the Americas
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TECHNICAL REPORT
I
Monitoring and evaluating changes in cannabis policies: insights from the Americas
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TECHNICAL REPORT
I
Monitoring and evaluating changes in cannabis policies: insights from the Americas
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TECHNICAL REPORT
I
Monitoring and evaluating changes in cannabis policies: insights from the Americas
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https://doi.org/10.1016/j.ypmed.2017.03.022.
Wang, G. S., Davies, S. D., Halmo, L. S., Sass, A. and Mistry, R. D. (2018), ‘Impact of marijuana
legalisation in Colorado on adolescent emergency and urgent care visits’,
Journal of
Adolescent Health
63, pp. 239-241. https://doi.org/10.1016/j.jadohealth.2017.12.010.
Wen, H. and Hockenberry, J. M. (2018), ‘Association of medical and adult-use marijuana laws with
opioid prescribing for Medicaid enrollees’,
JAMA Internal Medicine
178, pp. 673-679.
https://doi.org/10.1001/jamainternmed.2018.1007.
Wen, H., Hockenberry, J. M. and Cummings, J. R. (2015), ‘The effect of medical marijuana laws on
adolescent and adult use of marijuana, alcohol, and other substances’,
Journal of Health
Economics
42, pp. 64-80.
Wilkins, C. (2016), ‘After the legalisation of cannabis: the Cannabis Incorporated Society (CIS)
regulatory model for recreational cannabis in New Zealand’,
New Zealand Medical Journal
129, pp. 17-20.
Zuccato, E., Chiabrando, C., Castiglioni, S., Bagnati, R. and Fanelli, R. (2008), ‘Estimating community
drug abuse by wastewater analysis’,
Environmental Health Perspectives
116, pp. 1027-1032.
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
Appendix A: Identification and commentary on ongoing/planned
studies of legalisation
Here, we identify some ongoing or planned studies from the US, Uruguay and Canada that examine
the impacts of cannabis policy changes. This is not a comprehensive list; the goal is to highlight the
variety of studies being conducted, to learn more about cannabis and the consequences of various
policy changes.
US studies
Studies funded by the National Institutes of Health (NIH)
The NIH, largely through the National Institute on Drug Abuse (NIDA), has supported a broad portfolio
of research on cannabinoids and their use in the endocannabinoid system (
23
). This includes funding
ongoing research into the use of phytocannabinoids, purified cannabinoids, such as CBD and THC,
and synthetic cannabinoids. In FY 2017, the NIH funded research into cannabinoids to the value of
USD 140 million through various research arms, including NIDA (USD 88 million) and the National
Institute on Alcohol Abuse and Alcoholism (NIAAA) (USD 21 million). In addition, the NIH provided an
additional USD 36 million for research into therapeutic cannabinoids, allocating USD 16 million to
NIDA and USD 6.5 million to the National Institute on Alcohol Abuse and Alcoholism (NIAAA). The
NIH also provided an additional USD 15 million for research into CBD, USD 11 million of which went
to NIDA.
NIDA is currently undertaking several studies that are specific to cannabis use and the impacts of
legalisation. The most ambitious study is the Longitudinal Study of Adolescent Brain Cognitive
Development (the ABCD study), which aims to enrol almost 12 000 healthy children aged 9 and 10
years (singletons and twins) across the US and follow them into early adulthood. According to NIDA,
this is the largest long-term study of brain development and child health in the US.
The study, which is being carried out in partnership with the NIAAA, will examine how biology and
environmental factors relate to developmental and physical outcomes, including mental health and life
achievements. Researchers will employ brain imaging technology to evaluate changes over time.
Specific to cannabis legalisation, the study will examine the impact of the changing state and local
policies on youth drug use and related development. For example, it will examine the extent to which
casual or regular use of cannabis during adolescence has an impact on neurodevelopment in
adulthood.
The study is still currently enrolling participants. Since September 2016, researchers have enrolled
just over 10 000 participants. Baseline data obtained from the first 4 500 participants, suggest that
drug use among participants is minimal.
One active study by NIDA is looking at medical cannabis use among primary care patients in states
with legal medical and recreational cannabis laws. The aims of the Medical Cannabis Use among
Primary Care Patients study are to better understand the medical use of cannabis in a single, large
health system that asks patients about their cannabis use and to describe their cannabis use
behaviours and compare them with others who use cannabis without medical recommendations.
Studies funded by the National Institute of Justice (NIJ)
The NIJ is currently funding multiple studies that examine the impacts of cannabis in the US, including
( ) See
https://www.drugabuse.gov/drugs-abuse/marijuana/nih-research-marijuana-cannabinoids
23
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I
Monitoring and evaluating changes in cannabis policies: insights from the Americas
one study examining the effects of Colorado’s REC law on DUIs and crime (
24
). The NIJ has also
funded a USD 1 million study on the impacts of marijuana legislation on law enforcement and crime in
Washington state.
Studies funded by US states
Colorado (
25
) state has granted USD 9 million of public funds to cannabis research, dispersing the
funds across nine studies. The studies focus on the health benefits of using medical cannabis to treat
inflammatory bowel syndrome, Parkinson’s disease, epilepsy (two studies), post-traumatic stress
disorder (PTSD) (two studies), palliative care, insomnia and pain relief. The state has also funded
USD 2.4 million of research into the public health effects of REC, focusing on driving impairment, the
acute effects of dabbing (
26
), the concentration of cannabinoids in breast milk, use in older
populations, the adverse effects of edibles, cardiovascular effects and a general pre/post analysis of
broad public health impacts.
Under Washington (
27
) state’s initiative, a portion of cannabis tax revenue is earmarked for research.
For the period 2015-17, the Alcohol and Drug Abuse Institute of the University of Washington
received USD 454 000 from the state’s Dedicated Marijuana Fund. Current and ongoing research
focuses on areas of epidemiology, chronic pain management, impacts on driving and the efficacy of
innovative prevention programmes.
Uruguay
There are two ongoing academic monitoring and evaluation groups. The first is the Monitor Cannabis
Uruguay group, affiliated with the School of Social Science at the University of the Republic of
Uruguay. Monitor Cannabis Uruguay researches ongoing developments related to cannabis in the
country. Current ongoing research focuses on the impact of the law on security. The second
academic group is housed at the Catholic University of Uruguay, which maintains the Latin American
Marijuana Research Initiative (LAMRI) (
28
). LAMRI is funded by the Open Society Institute (a non-
governmental organisation that advocates drug policy reform) and evaluates ongoing cannabis policy
trends in Uruguay and the rest of the region. LAMRI-affiliated researchers have published papers on
consumption patterns, cannabis user opinions and cannabis club design in Uruguay.
The Uruguayan Drug Observatory published a preliminary study (
29
) in 2015 on drug use among
university students to evaluate their opinions, prevalence and source of cannabis. Though the law had
not been fully implemented, researchers included questions on home cultivation.
Canada
The Canadian government (
30
), through the Canadian Institute of Health Research, has allocated
CAD 1.4 million to study the effects of cannabis legalisation on certain groups and evaluate existing
regulatory models. Funds are to be distributed across 14 studies led by universities and hospitals,
looking at youth prevention, exposure in pregnancy, impaired driving, trajectories of cannabis use,
outcomes related to opioid use, cannabis use in the workplace, cannabis use in secondary schools,
monitoring mental health outcomes and provincial responses to federal legalisation. More recently,
Health Canada released tenders that focused on studies of cryptomarket cannabis sales and public
attitudes.
( ) See
https://www.nij.gov/topics/drugs/Pages/research-projects.aspx
25
( ) See
https://www.colorado.gov/pacific/cdphe/marijuana-research
26
( ) Dabbing is the action or practice of inhaling small quantities of a concentrated and vaporized drug, typically cannabis oil or
resin.
27
( ) See
http://learnaboutmarijuanawa.org/research.htm
28
( ) See
https://ucu.edu.uy/es/lamri
29
( ) See
http://www.cicad.oas.org/oid/pubs/UniversityStudyReport_Uruguay_SPA.pdf
30
( )
https://www.canada.ca/en/institutes-health-research/news/2018/01/cannabis_and_populationhealthresearch.html
24
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I
Monitoring and evaluating changes in cannabis policies: insights from the Americas
Appendix B: Research papers on the impacts of recreational cannabis laws
Shading indicates presence in text.
Reference
Location and
years evaluated
Control measures
Outcome
Independent
variable(s)
REC-specific
policy change
Data and methods
Findings
Peer-reviewed articles
Aydelotte et
al. (2017)
Washington and
Colorado
2009-15
States with similar
traffic and roadways:
Alabama, Indiana,
Kentucky, Missouri,
South Carolina,
Tennessee, Texas
and Wisconsin
Motor vehicle
crash fatality
REC
REC adoption
Annual number of motor
vehicle fatalities reported in
the Fatality Analysis
Reporting System;
difference-in-difference
approach; random effects
Pre recreational marijuana legalisation,
annual changes in motor vehicle crash
fatality rates for Washington and Colorado
were similar to those for the control states.
Post recreational marijuana legalisation,
changes in motor vehicle crash fatality
rates for Washington and Colorado also did
not significantly differ from those for the
control states (adjusted difference-in-
difference coefficient =
 +0.2
fatalities/billion
vehicle miles travelled; 95 % CI
−0.4
to
+0.9).
In the five years after legalisation, fatal
crash rates increased more in Colorado
and Washington than would be expected
had they continued to parallel crash rates in
the control states (+1.2 crashes/billion
vehicle miles travelled, CI: -0.6 to 2.1,
p = 0.087),
but not significantly so. The
effect was more pronounced and
statistically significant after the opening of
commercial dispensaries (+1.8
crashes/billion vehicle miles travelled, CI:
+0.4 to +3.7,
p = 0.020).
MED laws not associated with any reported
changes in cannabis use. REC laws were
associated with an 8 % decrease (OR,
0.92; 95 % CI, 0.87-0.96).
Aydelotte et
al. (2019)
Washington and
Colorado
2007-17
Hawaii, Montana,
New Mexico, Rhode
Island, Vermont,
Idaho, Kansas,
Nebraska, South
Dakota
Monthly motor
vehicle crash
fatality
REC
REC
implementation
(i.e., when
stores opened)
Annual number of motor
vehicle fatalities reported in
the Fatality Analysis
Reporting System;
difference-in-difference
approach; random effects
Anderson et
al. (2019)
States with MED
or REC laws
States without MED
or REC laws
Past-month
prevalence
rates
MED or REC
MED or REC
adoption
Past-month prevalence rates
for US high school students
from the Youth Risk
Behavioral Survey.
Multivariate logistic
regression for reporting
past-month use.
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
Reference
Bell et al.
(2015)
Location and
years evaluated
Colorado
January 2008-
August 2014
Control measures
Pre/post
Outcome
Burns
Independent
variable(s)
MED
REC
REC-specific
policy change
Pre REC to
MED/REC
enactment and
implementation
Data and methods
Cross-sectional analysis of
American Burn Association’s
National Burn Repository for
hydrocarbon burns
Findings
Twenty-nine patients with butane hash oil
burns were admitted to the local burn
centre during the study period. No cases
presented prior to medical liberalisation, 19
(61.3 %) presented during medical
liberalisation (October 2009 to December
2013) and 12 presented (38.7 %) in 2014,
after legalisation. The majority of patients
were Caucasian (72.4 %) and male
(89.7 %). The median age was 26 years
(range 15-58 years). The median total body
surface area covered by burns was 10 %
(range 1-90 %). The median length of
hospital admission was 10 days.
Many retailers had no security measure to
determine age (41 % in Colorado; 35 % in
Washington). Approximately 61 % of
retailers in Colorado and 44 % in
Washington made health claims about the
benefits of marijuana, including reduction in
anxiety, depression, insomnia and
pain/inflammation. Inferred demographic
characteristics of followers of Weedmaps
on Twitter and Instagram revealed that over
60 % were male and nearly 70 % or more
were aged 20-29 years, yet some (15-
18 %) were under the age of 20.
Longer REC duration (Odds ratio (OR)
vaping: 2.82, 95 % CI 2.24 to 3.55; OR
edibles: 3.82, 95 % CI 2.96 to 4.94) and a
higher dispensary density (OR vaping:
2.68, 95 % CI 2.12 to 3.38; OR edibles:
3.31, 95 % CI 2.56 to 4.26) were related to
a higher likelihood of trying vaping and
edibles. Permitting home cultivation was
related to a higher likelihood (OR 1.93,
95 % CI 1.50 to 2.48) and younger age at
onset (β
−0.30,
95 % CI
−0.45
to
−0.15)
of
consuming edibles.
Bierut et al.
(2017)
Washington and
Colorado
June-July 2015
None
Cannabis
advertising
online
REC
None
Cross-sectional sample of
licensed retailers that
advertise through
Weedmaps (n = 146; 89
from Colorado, 57 from
Washington); social media
followers of Weedmaps
(Twitter = 57 752;
Instagram = 2 249);
descriptive analysis and
non-parametric hypothesis
testing (chi-squared test)
Cross-sectional sample of
cannabis-using young
people (14 to 18 years;
n
= 2 630) surveyed online;
logistic and linear regression
Borodovsky et
al. (2017)
REC states
29 April 2016 to
18 May 2016
Non-REC states
Youth use of
cannabis,
including ever
vaping or ever
using edibles
REC,
operational
dispensary,
home
cultivation
Point in time
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
Reference
Cerdá et al.
(2017)
Location and
years evaluated
Washington and
Colorado
2010-12 and
2013-15
Control measures
Non-REC states
Outcome
Adolescent
past-month
marijuana
prevalence of
use and
perception
Independent
variable(s)
REC
REC-specific
policy change
Pre REC to REC
enactment and
implementation
Data and methods
Repeated cross-sectional
MTF surveys (n = 253 902);
difference-in-difference
approach to estimate
perception/use
Findings
In Washington, perceived harmfulness
declined by 14.2 % and 16.1 % among 8th
and 10th graders, respectively, while
marijuana use increased by 2.0 % and
4.1 % during the periods 2010-12 and
2013-15, respectively. In contrast, among
states that did not legalise REC, perceived
harmfulness decreased by 4.9 % and 7.2 %
among 8th and 10th graders, respectively,
and marijuana use decreased by 1.3 % and
0.9 % over the same periods. Difference-in-
difference estimates comparing
Washington with states that did not legalise
REC indicated that these differences were
significant for perceived harmfulness (8th
graders
−9.3
% (SD 3.5 %),
p
= 0.01; 10th
graders
−9.0
% (SD 3.8 %),
p
= 0.02) and
marijuana use (8th graders: % [SD], 5.0
[1.9];
p
= 0.03; 10th graders 3.2 % (SD
1.5 %),
p
= 0.007). No significant
differences were found regarding perceived
harmfulness or marijuana use among 12th
graders in Washington or for any of the
three grades in Colorado.
Among respondents aged 12 to 17 years,
past-year CUD increased from 2.18 % to
2.72 % after REC enactment, a 25 %
higher increase than that for the same age
group in states that did not enact REC
(odds ratio [OR], 1.25; 95 % CI, 1.01-1.55).
Unmeasured confounders would need to
be more prevalent in REC states and
increase the risk of cannabis use by 1.08 to
1.11 times to explain observed results,
indicating results that are sensitive to
omitted variables. No associations were
found among the respondents aged 18 to
25 years. Among respondents 26 years or
older, past-month marijuana use after REC
enactment increased from 5.65 % to
7.10 % (OR, 1.28; 95 % CI, 1.16-1.40),
past-month frequent use from 2.13 % to
2.62 % (OR, 1.24; 95 % CI, 1.08-1.41), and
past-year CUD from 0.90 % to 1.23 % (OR,
1.36; 95 % CI, 1.08-1.71).
Cerdá et al.
(2019)
Washington,
Colorado, Oregon
and Alaska
2008 to 2016
Non-REC states
Adolescent
past-month
marijuana
prevalence of
use and self-
reported
cannabis use
disorder
REC
3-level variable
determining
never passed
REC; before
REC enactment,
after REC
enactment
Repeated cross-sectional
NSDUH surveys; difference-
in-difference approach
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
Reference
Cheng et al.
(2018)
Location and
years evaluated
Colorado localities
January 2010-
August 2015
Control measures
Outcome
Housing
values
Independent
variable(s)
REC
REC-specific
policy change
Data and methods
Difference-in-difference
ordinary least squares
estimation
Findings
Legalisation leads to an average 6 %
increase in housing values, indicating that
the capitalised benefits outweigh the costs.
In addition, we find suggestive evidence
that this relatively large housing value
appreciation is probably because REC has
induced strong housing demand while
having no discernible effect on housing
supply. Finally, authors show that the effect
of REC is heterogeneous across locations
and property types.
Weighted estimates showed that 39 % of
the full sample and 9 % of non-marijuana
users supported marijuana legalisation.
Multivariable models showed that lower
marijuana harm perceptions and lifetime
and past 30-day tobacco use were
common predictors of support for marijuana
legalisation and intentions to use marijuana
among non-users of marijuana. State-level
marijuana policy was not associated with
the level of agreement for marijuana
legalisation.
Prevalence of past-year driving while under
the influence of marijuana was 43.6 %
among respondents. The prevalence of
driving within 1 hour of using marijuana at
least five times in the past month was
23.9 %. Increased perception that driving
high is unsafe was associated with lower
odds of past-year marijuana DUIs
(OR = 0.31,
p
< 0.01) and lower past-month
odds of driving five or more times within 1
hour of using marijuana (OR = 0.26,
p
< 0.01).
Cohn et al.
(2017)
US
October 2014
None
Young adult
opinion for
REC
Demographic
Point in time
Nationally representative
cross-sectional sample of
adults aged 18-34 years
from the Truth Initiative
Young Adult Cohort survey
(n = 3 532); multinomial
logistic regression
Davis et al.
(2016)
Colorado and
Washington
September 2014
None
Self-reported
driving while
intoxicated or
within 1 hour
of consuming
marijuana
Demographic
variables
Point in time
Online survey of past-month
users (n = 865; 399 from
Colorado, 446 from
Washington);
logistic regression
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
Reference
Dilley et al.
(2017)
Location and
years evaluated
Washington
June 2016
Control measures
None
Outcome
Local-level
regulations
and public
opinion
Independent
variable(s)
REC
REC-specific
policy change
Point in time
Data and methods
Descriptive assessment of
marijuana-related municipal
and county ordinances
(n = 181)
Findings
A total of 125 cities and 30 counties had
passed local ordinances to address
recreational marijuana retail sales. Multiple
communities implemented retail market
bans, including some temporary bans
(moratoria), while considering whether or
not to pursue other policy options. As of 30
June 2016, 30 % of the state population
lived in places that had temporarily or
permanently banned retail sales.
Communities frequently enacted zoning
policies that explicitly regulated where
marijuana businesses could be established.
Other policies included in ordinances
placed limits on business hours and
distance requirements (buffers) between
marijuana businesses and youth-related
land use types or other sensitive areas.
HYS shows statistically significant declines
in prevalence from 2010-2012 to 2014-
2016 among both 8th graders (from 9.8 %
[95 % CI, 9.1 %-10.5 %] to 7.3 % [95 % CI,
6.6 %-8.0 %];
P < .001)
and 10th graders
(from 19.8 % [95 % CI, 18.6 %-21.0 %] to
17.8 % [95 % CI, 16.7 %-18.9 %];
P = .01).
Findings indicated a significantly positive
correlation between marijuana-related
consequences and perceived risk post
legalisation. Despite relatively equal use in
both groups, adolescents in the legalisation
group experienced higher levels of
perceived risk and increased negative
consequences.
Current use increased among adults living
in areas within 18 miles of a retailer and,
especially, within 0.8 miles (odds ratio
[OR] = 1.45; 95 % confidence interval
[CI] = 1.24, 1.69). Frequent use increased
among adults living within 0.8 miles of a
retailer (OR = 1.43; 95 % CI = 1.15, 1.77).
Dilley et al.
(2019)
Washington
2010-12 and
2014-16
Pre/post REC
Past month
prevalence
Washington Healthy Youth
Survey of 8th, 10th, and
12th graders
Estoup et al.
(2016)
Washington
2010-15
Pre-REC cohort
Perceived risk
and frequency
of use of
marijuana in
adolescents
REC
No date or year
specified
Self-referred students with
problematic drug use,
enrolled in school-base
substance use intervention
(n = 262; 144 pre-
legalisation); mediation
model with non-parametric
hypothesis testing
Washington Behavioral Risk
Factor Surveillance System
(BRFSS)
Everson et al.
(2019)
Washington
2009-16
None. Proximity to
dispensary
Past month
prevalence
REC
REC enactment
and proximity to
nearest retail
outlet to
respondent ZIP
code
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
Reference
Fiala et al.
(2017)
Location and
years evaluated
Oregon
November 2015
and April-May
2016
Control measures
Pre/post
Outcome
Viewing
marijuana
promotion
Independent
variable(s)
Demographic
variable and
county of
residence
REC-specific
policy change
None
Data and methods
Repeated cross-sectional
online survey (n = 4 001) of
adults (18+ years); non-
parametric hypothesis
testing (chi-squared test).
Findings
More than half of adults (54.8 %) state-wide
reported seeing marijuana advertising in
the past month. These adults reported that
they most frequently saw store-front
(74.5 %), street-side (66.5 %) and billboard
(55.8 %) advertising. Exposure did not
significantly differ by participant’s age or
marijuana use but was higher among those
living in counties with retail sales (56.5 %)
than among those living in counties without
(32.5 %).
Independent of the effects of covariates,
densities of marijuana outlets were
unrelated to property and violent crimes in
local areas. However, the density of
marijuana outlets in spatially adjacent
areas was positively related to property
crime in spatially adjacent areas over time.
Furthermore, the density of marijuana
outlets in local and spatially adjacent block
groups was related to higher rates of
marijuana-specific crime. This study
suggests that the effects of the availability
of marijuana outlets on crime do not
necessarily materialise within the specific
areas where these outlets are located but
may materialise in adjacent areas.
Women who completed the intervention
after marijuana legalisation were
significantly more likely (OR = 2.1,
p
< 0.0001) to report marijuana use on
exiting the programme than women who
completed the intervention before
marijuana legalisation. Across both cohorts
(pre and post legalisation), the authors
found a positive link between marijuana
use on exit and alcohol, illegal methadone,
other opioids, amphetamines and cocaine
use.
Freisthler et
al. (2017)
Denver census
tracts
January 2013-
October 2015
None
Violent,
property and
marijuana-
specific crime
(crimes that
involved
marijuana and
licensed
facilities)
REC
MED/REC
dispensary
density over
time
Denver Police data of 481
census blocs over 34
months (n = 16 354);
Bayesian Poisson space-
time model
Grant et al.
(2017)
Washington
February 2001 to
July 2015
Pre-REC cohort
Self-reported
past-month
use of
marijuana in
pregnant
women
REC
Pre REC to REC
enactment and
implementation
Women enrolled in the
Parent-Child Assistance
Program (n = 1 359; pre
REC = 997, post
REC = 362); non-parametric
hypothesis testing (chi-
squared test)
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
Reference
Hall, K. E. et
al. (2018)
Location and
years evaluated
Colorado
2012-14
Control measures
Pre/post
Outcome
ED episodes
Independent
variable(s)
REC
REC-specific
policy change
Pre-REC to REC
implementation
Data and methods
Colorado Hospital
Association data
Findings
State-wide data demonstrated a fivefold
rise in the prevalence of mental health
diagnoses among cannabis-associated ED
visits (prevalence rate = 5.35, 95 % CI 5.27
to 5.43), compared with ED visits not
related to cannabis. The hospital
subpopulation supported this finding with a
fourfold rise in the prevalence of psychiatric
complaints among ED visits attributable to
cannabis (prevalence rate = 4.87, 95 %
CI 4.36 to 5.44), compared with ED visits
that were not attributable to cannabis.
State-wide rates of ED visits associated
with both cannabis and mental health
significantly increased from 224.5 per
100 000 in 2012 to 268.4 per 100 000 in
2014 (p < 0.0001).
Results indicate that there were no impacts
on the prices paid for medical or
recreational marijuana by state
representative residents within the short 4-
to 5-month window following legalisation.
However, there were differences in how
much people paid for marijuana for
recreational purposes from a recreational
store.
The prevalence of marijuana use in
Colorado college students is much higher
than the national average (71 % v 39 %,
respectively;
p
< 0.001), especially the
percentage of daily or almost daily users
(25 % v 2 %, respectively;
p
< 0.001).
There were significant differences found
between non-users of marijuana and the
marijuana users that use once a week or
more but not daily in regard to the grade
point average (F
(6,227)
= 2.935,
p
< 0.001).
In addition, it seems that the relationship
between alcohol and marijuana use in
general has decreased since Amendment
64 was passed but not among binge
drinkers.
Rates of Oregon college students’
marijuana use increased (relative to that of
students in other states) following
recreational marijuana legislation in 2015
but only for those who reported recent
heavy use of alcohol.
Hunt and
Pacula (2017)
Colorado and
Washington
October 2013,
May 2014,
October 2014
Pre-REC cohort
Reported retail
price
REC/MED
REC enactment
to REC
implementation
Longitudinal survey of three
waves (RAND Marijuana
Use in West Coast States
Survey) (n = 317 past-month
users);
Weedmap data on price
(n = 3 802); difference-in-
difference approach
Jones et al.
(2018)
Colorado
October 2013 to
March 2015
US (whether REC
was in place or not)
Frequency of
marijuana use
in college
students
REC
REC enactment
to REC
implementation
Repeated cross-sectional
surveys (n = 1 413; pre
REC = 424; post
REC = 989), compared with
responses from National
College Health Assessment
for 2015; parametric
hypothesis testing, ANOVA
Kerr, D. et al.
(2017)
Students in one
large public
university in
Oregon
2012-16
Students from six
universities in non-
REC states
Changes in
marijuana,
alcohol and
cigarette use
in college
students
REC
Pre REC to REC
enactment and
implementation
in July 2015
Repeated cross-sectional
survey (n = 10 924) of
undergraduates; mixed-
effects logistic regression
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TECHNICAL REPORT
I
Monitoring and evaluating changes in cannabis policies: insights from the Americas
Reference
Kerr, D. et al.
(2018)
Location and
years evaluated
University
students in
Oregon
2008-16
Control measures
Students from 123
other universities in
non-REC states
Outcome
Changes in
cannabis use
prevalence
Independent
variable(s)
REC
REC-specific
policy change
REC
implementation
Data and methods
Repeated cross-sectional
survey in Oregon (n = 7 412)
and 123 institutions (n =
274 340)
Findings
Following REC, Oregon students
(compared to non-REC-state students)
showed relative increases in rates of
marijuana use (odds ratio [OR] = 1.29,
95 % confidence interval [CI: 1.13, 1.48],
p
= .0002, and decreases in tobacco use
rates (OR = .71, 95 % CI [.60, .85],
p
< .0001).
A small increase of 1.2 percentage points
in past-year use prevalence, from 24.3 %
(22.3-26.5 %) to 25.6 % (23.6-27.6 %),
which is not statistically significant, was
found when combining the surveys. No
statistically significant change was found in
the prevalence of the simultaneous use of
cannabis and alcohol — it decreased from
12.9 % (11.3-14.7 %) to 12.6 % (11.0-
14.4 %).
Period effects were the main driver of rising
marijuana use prevalence. Models
including indicators of medical and
recreational marijuana policies did not find
any significant positive impacts.
The prevalence of hospitalisations for
marijuana exposure in patients aged 9
years and more than doubled after the
legalisation of medical marijuana (from 15
per 100 000 hospitalisations during the
period 2001-09 to 28 per 100 000
hospitalisations during the period 2010-13;
p
< 0.001), and ED visits nearly doubled
after the legalisation of recreational
marijuana (from 22 per 100 000 ED visits
during the period 2010-13 to 38 per
100 000 ED visits during January to June
2014;
p
< 0.001).
Kerr, W. C. et
al. (2018)
Washington
2012, 2014-15
None
Self-reported
past-year use
in survey year
and in 2012 in
adults
REC
Pre REC to REC
enactment and
implementation
Cross-sectional
representative phone
surveys (n = 3 451);
multinomial logistic
regression
Kerr, W. C. et
al. (2017)
Respondents in
states with
REC/MED policy
1984-2015
Respondents in
states without
REC/MED policy
Past-year
marijuana use
MED, REC,
provision for
dispensary,
home
cultivation
MED
REC
REC adoption
Repeated cross-sectional
quinquennial National
Alcohol Survey of adults
(18+) (n = 37 359);
fixed-effects approach for
age-period-cohort effects
Retrospective data from the
Colorado Hospital
Association, a consortium of
more than 100 hospitals in
the state; parametric
hypothesis testing
Kim and
Monte (2016)
Colorado
2001-14
Pre/post
ED episodes
for cannabis
Pre REC to
MED/REC
enactment and
implementation
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TECHNICAL REPORT
I
Monitoring and evaluating changes in cannabis policies: insights from the Americas
Reference
Kim et al.
(2016)
Location and
years evaluated
Colorado
2011-14
Control measures
Pre/post
Outcome
ED episodes
for cannabis
Independent
variable(s)
REC
REC-specific
policy change
Pre REC to
MED/REC
enactment and
implementation
Data and methods
Retrospective data from
Colorado Hospital
Association
Findings
The data from the Colorado Hospital
Association did not show a significant
change from 2011 to 2012 in the rate of ED
visits with ICD-9 codes of cannabis use
among out-of-state residents; however,
from 2012 to 2014, the state-wide rate
among out-of-state residents rose from 78
per 10 000 visits in 2012 to 112 per 10 000
visits in 2013 and 163 per 10 000 visits in
2014 (rate ratios, 1.44 (2012-13) and 1.46
(2013-14);
p
< 0.001 for both comparisons).
Among Colorado residents, from 2011 to
2014, the rate of ED visits possibly related
to cannabis use increased from 61 to 70,
86 and 101, respectively, per 10 000 visits
(rate ratios, 1.14 (2011-12), 1.24 (2012-13)
and 1.17 (2013-14);
p
< 0.001 for all
comparisons).
There was a pooled step increase of 1.08
traffic fatalities per million residents
followed by a trend reduction of
−0.06
per
month (both
P
< 0.001). The results
suggest that legalizing the sale of cannabis
for recreational use can lead to a temporary
increase in traffic fatalities in legalizing
states that can spill over into neighbouring
jurisdictions.
Lane and Hall
(2019)
Colorado,
Washington and
Oregon
2009-16
Kansas, Nebraska,
New Mexico,
Oklahoma and Utah
(Colorado
neighbours); British
Columbia and
Oregon (Washington
neighbours); and
California and
Nevada (Oregon
neighbours)
Pre/post
Monthly motor
vehicle
fatalities
REC
REC
implementation
in each state
Interrupted time series using
CDC WONDER data on
vehicle fatalities
Livingston et
al. (2017)
Colorado
2000-15
Monthly
opioid-related
fatalities
REC
REC
implementation
January 2014
Interrupted time series
Colorado’s legalisation of recreational
cannabis sales and use resulted in a 0.7
deaths-per-month (b =
−0.68;
95 % CI =
−1.34
to
−0.03)
reduction in opioid-related
deaths. This reduction represents a
reversal of the upwards trend in opioid-
related deaths in Colorado.
Findings suggest there are no negative
effects of legalisation on crime clearance
rates. Moreover, evidence suggests that
some crime clearance rates have
improved. Our findings suggest legalisation
has resulted in improvements in some
clearance rates.
Makin et al.
(2018)
Colorado and
Washington
2010-15
The rest of the US
as one unit
Violent and
property crime
clearance
rates
REC
Pre REC to REC
enactment
Monthly counts of crime
from FBI Uniform Crime
Reporting data; interrupted
time-series analysis
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TECHNICAL REPORT
I
Monitoring and evaluating changes in cannabis policies: insights from the Americas
Reference
Mason et al.
(2016)
Location and
years evaluated
Washington
2010/11 to
2013/14
Control measures
Pre-REC cohort
Outcome
Self-reported
past-month
use in
adolescents
Independent
variable(s)
Second survey
wave (just
prior to REC)
REC-specific
policy change
Pre REC to REC
enactment
Data and methods
Two wave cohort study of
8th/9th graders from
Tacoma, Washington
(n = 238); multivariate,
multilevel modelling
Nationally representative
sample of US adults
(n = 979; 334 from Colorado,
Washington, Arkansas,
Oregon, DC);
ordered logit and non-
parametric hypothesis
testing (chi square)
Findings
Marijuana use was higher for the second
cohort than for the first cohort, but this
difference was not statistically significant.
Rates of cigarette and alcohol use were
slightly lower in the second cohort than in
the first cohort.
Respondents rated pro-legalisation
arguments highlighting beneficial economic
and criminal justice consequences as more
persuasive than anti-legalisation
arguments, emphasising adverse public
health effects. Respondents were more
likely to agree with arguments highlighting
legalisation’s potential to increase tax
revenue (63.9 %) and reduce prison
overcrowding (62.8 %) than arguments
emphasising the negative consequences of
motor vehicle crashes (51.8 %) and youth
health (49.6 %). The highest rated anti-
legalisation arguments highlighted the
conflict between state and federal
marijuana laws (63.0 %) and asserted that
legalisation will fail to eliminate the illicit
market (57.2 %). Respondents who
endorsed pro-legalisation economic and
criminal justice arguments were more likely
than other respondents to support
legalisation. Respondents living in
Arkansas, Colorado, DC, Oregon and
Washington were significantly (p < 0.05)
more likely to agree with 11 of the 13 pro-
legalisation arguments and significantly
less likely to agree with 10 of the 13 anti-
legalisation arguments than respondents
living in non-legalisation states.
Students at Washington State University
experienced a significant increase in
marijuana use after legalisation. This
increase is larger than the increase that
would be predicted by national trends. The
change is strongest among females, Black
students and Hispanic students. The
increase for underage students is as much
as that for legal-age students. We find no
corresponding changes in the consumption
of tobacco, alcohol or other drugs.
McGinty et al.
(2017)
Respondents in
states that passed
REC
April 2016
Respondents in
states that did not
pass REC
Public opinion
and
arguments
for/against
legalisation
REC
Point in time
Miller et al.
(2017)
Washington
2005-15
Pre-REC cohort
Past-month
marijuana use
in college
students
REC
Pre REC to REC
enactment and
implementation
Repeated cross-sectional
surveys of undergraduates
at Washington State
University who participated
in the National College
Health Assessment
(n = 13 335); logit and OLS
regression
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TECHNICAL REPORT
I
Monitoring and evaluating changes in cannabis policies: insights from the Americas
Reference
Pacula et al.
(2016)
Location and
years evaluated
Colorado and
Washington
October 2013
Control measures
Oregon and New
Mexico
Outcome
Prevalence
rates and use
behaviours
between MED
and REC
users
Independent
variable(s)
REC
REC-specific
policy change
Point-in-time
measure during
REC enactment
Data and methods
Cross-sectional sample of
representative phone survey
(n = 1 994;
Washington = 787,
Oregon = 506;
Colorado = 503; New
Mexico = 213)
Findings
Recreational use is considerably higher
than medical use across all states (41 %),
but it is the highest in Oregon and
Washington. Approximately 86 % of people
who report ever using cannabis for
medicinal purposes also use it
recreationally. Fewer than one in five
recreational users report simultaneous use
of alcohol and cannabis most or all of the
time, and fewer than 3 % of medicinal
users report frequent simultaneous use of
alcohol and cannabis. In the US, the
degree of overlap between medicinal and
recreational cannabis users is 86 %.
Medicinal and recreational cannabis users
favour different modes and amounts of
consumption.
Cannabis use has increased for all
students since recreational legalisation, but
more so for those over 21 years. No
differences in past-month use frequency
were found between pre- and post-
legalisation. The influence of cannabis laws
on non-resident students’ decision to attend
a Colorado college predicted lifetime and
past 30-day use. In addition, out-of-state
students reported higher past 30-day use
than in-state students.
In communities opting out of sales, the
prior-to-legalisation cohort was less likely to
increase their willingness and intent to use
marijuana, and the legalisation cohort was
more likely to increase their intent to use.
For young people who used marijuana,
legalisation was associated with increased
use, and those in communities opting out of
sales experienced a larger growth in
marijuana use. Community policy appears
to impact young people’s attitudes towards
and use of marijuana. The results suggest
that the legalisation of recreational
marijuana did not increase marijuana use
among young people who did not use
marijuana, but it did increase use among
young people who were already using.
Parnes et al.
(2018)
Colorado
Spring 2013 to
autumn 2015
Pre-REC cohort
Self-reported
cannabis use
in college
students
REC
REC enactment
to
implementation
Undergraduate survey
(n = 5 241); non-parametric
hypothesis test (chi-squared
test)
Rusby et al.
(2018)
Oregon
Spring 2014 and
2015
Pre-REC cohort
Self-reported
cannabis use
in adolescents
REC
REC enactment
to
implementation
Two cohorts of 8th/9th
graders (n = 444);
multivariate linear regression
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TECHNICAL REPORT
I
Monitoring and evaluating changes in cannabis policies: insights from the Americas
Reference
Smart et al.
(2017)
Location and
years evaluated
Washington
July 2014-
September 2016
Control measures
None
Outcome
Changes in
price, potency
and product
Independent
variable(s)
REC
REC-specific
policy change
Post REC
implementation
only
Data and methods
Transaction sale data from
regulators
Findings
Traditional cannabis flowers still account for
the majority of spending (66.6 %), but the
market share of extracts for inhalation
increased by 145.8 % between October
2014 and September 2016, now comprising
21.2 % of sales. The average THC-level for
cannabis extracts is more than triple that
for cannabis flowers (68.7 % compared to
20.6 %). For flower products, there is a
statistically significant relationship between
price per gram and both THC [coefficient =
0.012; 95 % confidence interval (CI) =
0.011–0.013] and CBD (coefficient = 0.017;
CI = 0.015–0.019).
The estimated discount elasticity is +0.06
(CI = +0.07 to +0.05). Traditional cannabis
flowers still account for the majority of
spending (66.6 %), but the market share of
extracts for inhalation increased by
145.8 % between October 2014 and
September 2016, now accounting for
21.2 % of sales. The average THC level for
cannabis extracts is more than triple that
for cannabis flowers (68.7 % compared
with 20.6 %). For flower products, there is a
statistically significant relationship between
price per gram and both THC
(coefficient = 0.012; 95 % CI 0.011 to
0.013) and CBD (coefficient = 0.017; 95 %
CI 0.015 to 0.019). The estimated discount
elasticity is –0.06 (95 % CI –0.07 to –0.05).
Subbaraman
and Kerr
(2016)
Washington
January-October
2014
Pre/post
Support for
legalisation
Demographic
variable
Post REC
implementation
Random digit dialling of
residents (n = 2007);
bivariate tests and
multivariate regressions
Less than 5 % of those who voted for
marijuana legalisation would change their
vote, whereas 14 % of those who voted
against legalisation would change their
vote. In multivariable models controlling for
demographics, substance use and
marijuana-related opinions, those who
voted for legalisation had half the odds of
changing their vote than those who voted
against it. Among past-year non-marijuana
users, almost 10 % were somewhat/very
likely to use marijuana if they could buy it
from a legal store.
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TECHNICAL REPORT
I
Monitoring and evaluating changes in cannabis policies: insights from the Americas
Reference
Sokoya et al.
(2018)
Location and
years evaluated
Denver, Colorado
2012-15
Control measures
Pre/post
Outcome
ED visits
Independent
variable(s)
REC
REC-specific
policy change
Pre REC to
MED/REC
enactment and
implementation
Data and methods
Hospital data from the
University of Colorado
Hospital and Denver Health
Medical Centre;
non-parametric hypothesis
test
Wang et al.
(2016)
Colorado
2009-15
Pre/post
Paediatric
exposures to
marijuana
MED
REC
Pre REC to
MED/REC
enactment and
implementation
Retrospective cohort study
of hospital child admissions
at Children’s Hospital
Colorado and cannabis
exposure incidents reported
to poison control;
Poisson regression
Findings
Maxillary and skull base fracture
proportions significantly increased following
legalisation (p < 0.001 and
p
< 0.001,
respectively). No significant differences
were seen in the proportion of patients who
lived in urban and rural counties before and
after legalisation (p > 0.05).
The mean rate of marijuana-related visits to
the children’s hospital increased from 1.2
per 100 000 population 2 years prior to
legalisation to 2.3 per 100 000 population 2
years after legalisation (p = 0.02). Annual
poison control paediatric marijuana cases
increased more than fivefold from 2009 (9)
to 2015 (47). Colorado had an average
increase in poison control cases of 34 %
(p < 0 .001) per year, while the remainder
of the US had an increase of 19 %
p
<  0.001).
From 2000 to 2015, hospitalisation rates
with marijuana-related billing codes
increased from 274 per 100 000
hospitalisations to 593. Overall, the
prevalence of mental illness among ED
visits with marijuana-related codes was five
times higher (5.07, 95 % CI 5.0 to 5.1) than
the prevalence of mental illness among ED
visits without marijuana-related codes.
Poison control calls remained constant
from 2000 to 2009. However, in 2010, after
local medical marijuana policy
liberalisation, the number of marijuana
exposure calls significantly increased, from
42 to 93; in 2014, after recreational
legalisation, calls significantly increased by
79.7 %, from 123 to 221 (p < 0.0001).
Marijuana-related visits increased from 1.8
per 1 000 visits in 2009 to 4.9 in 2015
(p = <  0.0001).
Wang et al.
(2017)
Colorado
2000-15
Pre/post
Annual rates
of
hospitalisation
s, ED events
and poison
control calls
for marijuana
MED
REC
Pre REC to
MED/REC
enactment and
implementation
Univariate Poisson
regression
Wang et al.
(2018)
Colorado
2005-15
Pre/post
Children ED
visits for
cannabis
REC
MED
Pre REC to
MED/REC
enactment and
implementation
Retrospective review of
annual number of marijuana-
related visits to ED
(n = 4 202)
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TECHNICAL REPORT
I
Monitoring and evaluating changes in cannabis policies: insights from the Americas
Reference
Wen and
Hockenberry
(2018)
Location and
years evaluated
Alaska, Colorado,
Oregon and
Washington
Q1 2011 to Q2
2016
Control measures
Non-REC states
Outcome
State-level
opioid
prescribing
rates covered
by Medicaid
Independent
variable(s)
MED
REC
REC-specific
policy change
REC
implementation
Data and methods
State drug utilisation data
from the Centres for
Medicare and Medicaid
Services;
difference-in-difference
approach, two-way fixed
effects
Findings
The state implementation of medical
marijuana laws was associated with a
5.88 % lower rate of opioid prescribing
(95 % CI
−11.55
% to approximately
−0.21
%). Moreover, the implementation of
adult-use marijuana laws, which all
occurred in states with existing medical
marijuana laws, was associated with a
6.38 % lower rate of opioid prescribing
(95 % CI
−12.20
% to approximately
−0.56
%).
Regardless of store type, marijuana stores
were more likely to be located in
neighbourhoods that had a lower proportion
of young people, a larger racial and ethnic
minority population, a lower household
income, a higher crime rate or a greater
density of on-premise alcohol outlets. The
availability of medical and recreational
marijuana stores was differentially
correlated with household income and
racial and ethnic composition.
Shi et al.
(2016)
Census tracts in
Colorado
2015
REC and MED
store density
MED
REC
Cross-sectional ecological
study of all census tracts in
the state (n = 1 249);
parametric hypothesis
testing
Working papers
Hansen et al.
(2017b)
Washington
2015
Pre/post
Inter-state
trafficking after
REC
implementatio
n in Oregon
REC (opening
of retail stores
in Oregon)
REC
implementation
in Oregon
Washington retail
transaction data;
regression discontinuity
design
Washington retailers situated along the
Oregon border experienced a 41 % decline
in sales immediately following Oregon’s
cannabis market opening. In counties that
are the closest crossing point for the
majority of the neighbouring population, the
estimated decline in sales has grown to
58 % and is the largest for the biggest
transactions.
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TECHNICAL REPORT
I
Monitoring and evaluating changes in cannabis policies: insights from the Americas
Reference
Hansen et al.
(2018)
Location and
years evaluated
Washington and
Colorado
2000-16
Control measures
Non-REC states in
the US
Outcome
Motor vehicle
crash fatality
Independent
variable(s)
REC
REC-specific
policy change
REC
implementation
in 2014
Data and methods
Annual number of motor
vehicle fatalities reported in
the Fatality Analysis
Reporting System; synthetic
control approach
Findings
Between 2013 and 2016, the number of
drivers who tested positive for THC
increased in Colorado and Washington, by
92 % and 28 % respectively. However,
identifying a causal effect is difficult
because of the presence of significant
confounding factors. Hansen et al. found
that ‘the synthetic control groups saw
similar changes in marijuana-related,
alcohol-related and overall traffic fatality
rates despite not legalising recreational
marijuana’.
There is no conclusive evidence that
marijuana sale/manufacture arrests, DUI
arrests or opium/cocaine possession
arrests in border states are affected by
REC. The NSDUH data show that self-
reported marijuana use in states that
border REC states increased after REC,
compared with those states that do not
share borders with REC states.
Results from single-state analyses as well
as the combination of the three states
indicate that collision claim frequencies
increased significantly when retail sales
commenced. When states are examined
individually, the frequency of collision
claims increases by between 4.5 % and
13.9 %. A single analysis that combined the
three states with legal recreational use
found a smaller yet significant increase of
2.7 %.
Hao and
Cowan (2017)
Counties in
Washington and
Colorado
2009-14
Counties in
neighbouring states
just over the border
Arrests and
self-reported
marijuana use
REC
Pre REC to REC
enactment
FBI Uniform Crime
Reporting Data at county
level; NSDUH state-level
prevalence data; difference-
in-difference approach,
synthetic controls for
robustness check
Highway Loss
Data Institute
(2017)
Colorado,
Washington and
Oregon
January 2012 to
October 2016
Neighbouring states:
Nebraska, Utah,
Wyoming, Montana,
Idaho and Nevada
Auto
insurance
collision claim
rates
REC
REC
implementation
Monthly insurance collision
claims; Poisson regression
and non-parametric
hypothesis testing
REC, recreational marijuana law; MED, medical marijuana law; SD, standard deviation; ANOVA, analysis of variance; OLS, ordinary least squares.
REC adoption: when an initiative was passed by voters but was not in effect.
REC enactment: when laws were put into place to effect a legal change.
REC implementation: when the laws were fully operational and stores were open. Note: advocate-produced reports are not included.
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TECHNICAL REPORT
I
Monitoring and evaluating changes in cannabis policies: insights from the Americas
Appendix C: Additional trend data
Prevalence
In the figures below, we plot prevalence rates reported by the NSDUH for various age cohorts and states.
To help the reader, we also include a reference table of legal MED/REC dates of adoption and
implementation, the latter referring to when qualified patients or adults were able to access and use
cannabis. Keep in mind that many early MED states did not have any dispensaries or commercial store
fronts for several years after adopting or implementing MED.
TABLE AC1
Dates of MED/REC adoption and implementation
Medical cannabis
State
Alaska
Colorado
District of Columbia
Oregon
Washington
Adoption
November 1998
November 2000
November 1998
November 1998
November 1998
Year that stores
legally opened
NA
2005
2010
2009
NA
Adoption
November 2014
November 2012
November 2014
November 2014
November 2012
Recreational cannabis
Implementation
October 2016
January 2014
February 2015
October 2015
July 2014
The series of charts below plot the past-month prevalence rate of use of cannabis among the general
population (aged 12 and over) in Alaska, Colorado, DC, Oregon, Washington and the US as a whole
between 2003 and 2017. State estimates were taken from the NSDUH’s 2-year pooled estimates,
assigning the latter year for each of the year (e.g. pooled estimates for 2016 to 2017 represent 2017). To
show the change in prevalence rates relative to policy changes, we have plotted vertical dashed/dotted
lines to indicate the year in which MED dispensaries opened (a dotted line, where applicable), when REC
was adopted (i.e. voted into law; this is represented by a light-grey dashed line) and when REC was
implemented (i.e. when stores started opening; this is represented by a dark-grey dashed line). Because
we are using annual data, these vertical lines roughly approximate the timing of a policy change. For
example, voters of a state may have adopted REC in November 2014, even though the year was nearly
over after the law passed.
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 REU, Alm.del - 2023-24 - Endeligt svar på spørgsmål 746: Spm. om indhentning af erfaringer fra de stater i USA og Canada, som har legaliseret cannabis
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TECHNICAL REPORT
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
FIGURE AC1
Past-month cannabis use prevalence (%) in Alaska among those aged 12 years and older
20
15
10
5
0
2003
2004
2005
2006
Alaska
2007
2008
US
2009
2010
2011
2012
2013
2014
2015
2016
2017
REC Adoption
REC Implement
Source: NSDUH
FIGURE AC2
Past-month cannabis use prevalence (%) in Colorado among those aged 12 years and older
20
15
10
5
0
2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017
Colorado
US
REC Adoption
REC Implement
MED store
Source: NSDUH
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 REU, Alm.del - 2023-24 - Endeligt svar på spørgsmål 746: Spm. om indhentning af erfaringer fra de stater i USA og Canada, som har legaliseret cannabis
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TECHNICAL REPORT
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
FIGURE AC3
Past-month cannabis use prevalence (%) in DC among those aged 12 years and older
20
15
10
5
0
2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017
DC
US
REC Adopt
REC Implement
MED store
Source: NSDUH
FIGURE AC4
Past-month cannabis use prevalence (%) in Oregon among those aged 12 years and older
20
15
10
5
0
2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017
Oregon
US
REC Adopt
REC Implement
MED store
Source: NSDUH
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 REU, Alm.del - 2023-24 - Endeligt svar på spørgsmål 746: Spm. om indhentning af erfaringer fra de stater i USA og Canada, som har legaliseret cannabis
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TECHNICAL REPORT
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
FIGURE AC5
Past-month cannabis use prevalence (%) in Washington state among those aged 12 years and
older
20
15
10
5
0
2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017
Washington
US
REC Adopt
REC Implement
Source: NSDUH
Data from the MTF survey show little change in past-month cannabis use among 8th, 10th and 12th
graders (pooled) between 2009 and 2017. In 2009, 13.8 % of respondents reported using cannabis at
least once in the past month. This rate peaked in 2013, at 15.6 %, declining to 14.5 % in 2017. However,
past-month use rates have steadily increased among college students. In 2009, 18.5 % of respondents
reported using cannabis at least once in the past month. By 2016, the rate had climbed to 22.2 %.
Data from biennial state surveys add additional information to the changes in prevalence rates among
high school students post REC. These state surveys randomly sample students from selected middle
schools and high schools. The HKCS sampled about 17 000 students from 157 schools across the state
in 2015. The Washington state’s HYS surveyed over 230 000 students in over 1 000 schools in 2016. In
Table AC2 we report available prevalence estimates for high school students and adults reported in state
surveys in recent years, along with estimates from the Behaviour Risk Factor Surveillance System
(BRFSS) of the Centers for Disease Control and Prevention. However, past-month prevalence rates
among high school students or 12th graders have remained flat or declined in both states.
72
 REU, Alm.del - 2023-24 - Endeligt svar på spørgsmål 746: Spm. om indhentning af erfaringer fra de stater i USA og Canada, som har legaliseret cannabis
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TECHNICAL REPORT
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
TABLE AC2
Surveys and reported past-month cannabis prevalence rates for Colorado and Washington
Survey
Colorado, past-month (18+) BRFSS
Colorado, daily/near-daily (18+) BRFSS
Colorado, past-month (high school) HKCS*
Washington, past-month (12th grade) HYS
Washington, heavy past-month (12th grade) HYS**
*Estimates are for odd years; otherwise they are even.
**Heavy use is defined as using on 10+ days in the last 30.
25
26
22
27
9
2009/10
2011/12
2013/14
13.6
6
20
27
10
2015/16
13.5
6.35
21
26
11
Hospital and poison control centres
Data from hospitals and poison control centres allow researchers to gauge the initial public health
incidents associated with post-REC implementation. Below we plot the rate of ED events and
hospitalisations involving cannabis. ED episodes have increased since 2011 but not as rapidly as
hospitalisations. Rates remained relatively flat until 2013, when they started to rise just prior to REC
enactment. Data for 2015 are an estimated annual rate, as only counts from January to September are
publicly available. We were unable to find ED or hospitalisation data from Washington state.
FIGURE AC6
Adverse events involving cannabis per 100 000 population in Colorado
4000
3000
2000
1000
0
2009
2010
2011
ED
2012
Hospitalizations
2013
2014
2015
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 REU, Alm.del - 2023-24 - Endeligt svar på spørgsmål 746: Spm. om indhentning af erfaringer fra de stater i USA og Canada, som har legaliseret cannabis
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TECHNICAL REPORT
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
The figure below shows the reported calls to poison control centres involving cannabis per 100 000
residents for both Washington and Colorado. In Colorado since 2011, calls involving cannabis between
2011 and 2014, when they levelled off in 2014 at about 4 per 100 000. Washington saw a similar
increase, with rates rising in 2014, then levelling off for 2 years before rising again in 2016/17 to similar
per capita rates as in Colorado.
FIGURE AC7
Poison control calls per 100 000 population
5
4
3
2
1
0
2009
2010
2011
2012
Colorado
2013
2014
Washington
2015
2016
2017
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 REU, Alm.del - 2023-24 - Endeligt svar på spørgsmål 746: Spm. om indhentning af erfaringer fra de stater i USA og Canada, som har legaliseret cannabis
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TECHNICAL REPORT
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
Traffic fatalities
The National Highway Traffic Safety Administration’s Fatality Analysis Reporting System (FARS) reports
data on the number of traffic fatalities per 100 million vehicle miles travelled. The rate of traffic fatalities in
most states analysed was fairly linear between 2009 and 2017 (the obvious exceptions are DC, which is
mostly urban, and Alaska, which is mostly rural; both may suffer from extreme year-to-year variability).
However, starting around 2013, Oregon, Colorado and Washington show a marked increase compared
with the rest of the US.
FIGURE AC8
Traffic fatality rate per 100 million vehicle miles travelled
2.0
1.5
1.0
0.5
0.0
2009
2010
Alaska
2011
Colorado
2012
DC
2013
2014
Oregon
2015
Washington
2016
US
2017
Source: FARS
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 REU, Alm.del - 2023-24 - Endeligt svar på spørgsmål 746: Spm. om indhentning af erfaringer fra de stater i USA og Canada, som har legaliseret cannabis
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TECHNICAL REPORT
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Monitoring and evaluating changes in cannabis policies: insights from the Americas
Arrests for cannabis possession and supply offences
The figures below show rates of arrest for cannabis offences over time (where available). In all three
states, arrest rates for cannabis offences have declined over the period.
FIGURE AC9
Cannabis possession arrests per 100 000 population
350
300
250
200
150
100
50
0
2012
2013
Alaska
2014
Washington
2015
Colorado
2016
FIGURE AC10
Cannabis supply arrests per 100 000 population
20
15
10
5
0
2012
2013
Alaska
2014
Washington
2015
Colorado
2016
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