A systematic review of 61 longitudinal studies found mixed effects of recreational cannabis legalization, with some increases in young adult use and cannabis-related healthcare visits but minimal impact on adolescent use.
Read this if you want an evidence-based overview of what actually happens when recreational cannabis is legalized.
61 studiesLongitudinal studies reviewed on recreational cannabis legalization impacts
What the researchers found
Five outcome categories emerged: (1) Cannabis/substance use: some evidence of increased young adult use, minimal change in adolescent rates; (2) Attitudes: mixed evidence on changing perceptions; (3) Healthcare: increased cannabis-related visits; (4) Driving: some evidence of increased impaired driving; (5) Crime: mixed findings. The overall pattern shows some negative consequences but no large-magnitude short-term impacts. Most studies were from the US (66.2%).
Why it matters
As more jurisdictions consider legalization, policymakers need evidence on actual outcomes. This review shows the effects are more nuanced than either side of the legalization debate suggests.
The numbers in context
- 61 longitudinal studies included (2016-2022)
- 66.2% from the United States
- 5 outcome categories identified
- Some increase in young adult cannabis use
- Minimal change in adolescent use rates
- Increased cannabis-related healthcare visits
- Some evidence of increased impaired driving
How the study worked
Systematic review of longitudinal studies evaluating recreational cannabis legalization impacts, published 2016-2022. Comprehensive bibliographic search strategy.
Who was studied
General population across jurisdictions with recreational cannabis legalization (primarily US)
What this study cannot tell us
Most studies from the US, limiting generalizability. Short follow-up periods in many studies. Difficulty isolating legalization effects from other concurrent changes. Heterogeneity in legalization models across jurisdictions.
How to read the evidence
Systematic review of predominantly quasi-experimental studies. Strong synthesis methodology but limited by the quality and geographic concentration of underlying evidence.
When this study was published
Published in 2023. Covers the first wave of legalization outcome research.
The bigger picture
The cannabis legalization experiment is still young, and long-term outcomes remain unknown. The mixed findings highlight that legalization is not a single intervention — the details of implementation (pricing, retail access, advertising rules) likely matter more than the binary legal status.
Questions still open
- Will negative consequences grow as legal markets mature and prices drop?
- Do different legalization models (public vs private retail) produce different outcomes?
- What is the long-term trajectory of adolescent use in legalized jurisdictions?
Read the original research
The Impact of Recreational Cannabis Legalization on Cannabis Use and Associated Outcomes: A Systematic Review.
Substance abuse : research and treatment, 17, 11782218231172054
Citation
Farrelly, Kyra N; Wardell, Jeffrey D; Marsden, Emma; Scarfe, Molly L; Najdzionek, Peter; Turna, Jasmine; MacKillop, James. (2023). The Impact of Recreational Cannabis Legalization on Cannabis Use and Associated Outcomes: A Systematic Review.. Substance abuse : research and treatment, 17, 11782218231172054. https://doi.org/10.1177/11782218231172054