Monitoring and Evaluating Cannabis Legalisation

What is the issue?

The past decade has witnessed dramatic changes to the cannabis policy landscape in the Americas. While individual U.S. states began introducing medical cannabis laws as far back as the 1990s, the 2012 passing of nonmedical or ‘recreational’ legalisation laws in Colorado and Washington State was followed by a succession of similar laws being passed in more than 20 other states over the next 12 years. Outside of the U.S., Uruguay and Canada passed national-level recreational cannabis laws in 2013 and 2018 respectively.

While this project focused on the Americas, there have also been recent noteworthy changes to recreational cannabis policies in Europe and Australia. In Europe, Germany, Luxembourg and Malta laws were passed to legalise home cultivation for adults, and Germany and Malta introduced regulation for cannabis social clubs. In Australia, the Australian Capital Territory legalised home production and possession of cannabis for personal use. Other European jurisdictions are considering or experimenting with changes to their recreational cannabis laws (e.g., Czech Republic, Switzerland and the Netherlands).

There has been extensive research exploring the impacts of such legal changes on a range of public health, social, economic, crime and justice, and other outcomes. In this review, the researchers examined and summarised this evidence, producing one of the most comprehensive reviews of the impact of nonmedical cannabis policies in the Americas to date.

How did we help?

RAND was commissioned by the EU Drugs Agency (EUDA) to update a previous report, released in 2020 which covered research up to July 2018: Monitoring and evaluating changes in cannabis policies: insights from the Americas. In the updated review, RAND researchers conducted a rapid evidence assessment of research published between July 2018 and October 2023 to explore and monitor the impact of recreational cannabis policies—such as legalisation and the opening of retail markets—on any outcome.

Due to the large number of eligible studies, the researchers only included those that 1) used a quasi-experimental design with a control group (e.g., difference-in-differences methods) or an interrupted time series analysis where the pre-period was the control group; 2) included pre- and post- time periods; and 3) had representative samples (or weighted to become representative).

The literature encountered in this study explored the impact of these policies on a diverse range of outcomes, including:

• Perceptions and attitudes towards cannabis
• Cannabis use-related outcomes (e.g., prevalence of use, frequent use, initiation, and cannabis use disorders)
• Other substance use (e.g., alcohol, tobacco) and behaviours
• Traffic collisions and fatalities
• Healthcare-related outcomes (e.g., cannabis-related emergency department visits, cannabis hyperemesis)
• Cannabis market-related outcomes (e.g., medical cannabis market indicators, illegal market indicators and legal market indicators)
• Crime and criminal justice outcomes
• Labour market and economic outcomes.

What did we find?

RAND researchers extracted data from 178 studies from the U.S., Canada and Uruguay. Most studies used data from the U.S. (80%). Select findings from the review include:

Nonmedical cannabis legalisation policies were associated with statistically significant increases in past year and past month prevalence of cannabis use among U.S. adults. The literature also generally pointed towards positive statistically significant associations with cannabis use initiation, again when focusing on the U.S. context. Findings pertaining to other use-related outcomes, including use frequency, use initiation and cannabis use disorder (CUD) rates were mixed.

Nonmedical legalisation in the U.S. was associated with statistically significant reductions in prescriptions for opioid analgesic prescriptions. A smaller subset of literature indicated potential additional associations between these policies and decreases in overdose fatalities and hospital admissions related to these substances. However, it's important to acknowledge that these findings should be interpreted with caution, considering the specific context of the U.S., where many studies included data from periods coinciding with broader initiatives aimed at curbing the prescription and misuse of analgesic opioids.

Nonmedical cannabis legalisation was associated with statistically significant reductions in cannabis-specific arrests among adults. This outcome may not be surprising, as such policies typically remove the criminal status of most cannabis possession offenses. However, certain studies have also observed that cannabis-related arrest rates were already on a downward trend before legalisation, which could be indicative of broader changes in attitudes of law enforcement towards cannabis-specific offences.

The evidence on the impact of nonmedical cannabis policies on traffic fatalities or collisions differed depending on how legalisation polices were operationalised. There did not seem to be much support for the argument that the effective date of nonmedical legalisation in the U.S. was associated with motor vehicle fatality rates; however, U.S. studies that focused on the presence of nonmedical retail stores found a positive and statistically significant association with traffic fatalities.

The evidence base on nonmedical cannabis legalisation has grown dramatically since the EUDA published the first edition of this review (EUDA, 2020). Not only has the number of studies increased, the quality of the empirical methods used has also improved. Despite the increased number of publications, there remains a lot of uncertainty about the consequences of these policy changes, particularly with non-commercial markets, such as the ones emerging in Europe (e.g., cannabis social clubs).

Project team