What we know about how cannabis legalization affects substance use: a policy review
Medical cannabis laws appear to increase adult cannabis use without affecting adolescent use, and may reduce some opioid harms, while recreational law effects on adolescent use also appear minimal so far.
Quick Facts
What This Study Found
MCLs increase adult but not adolescent cannabis use. Less regulated supply provisions may increase adult cannabis use disorders. Some evidence suggests MCLs reduce opioid-related harms. Effects on alcohol and tobacco are uncertain. RCLs show little impact on adolescent prevalence but may increase college student use. Effects of RCLs on other substance use are unknown.
Key Numbers
MCLs increase adult cannabis use but not adolescent use. MCLs may increase adult CUD when supply is less regulated. RCLs show little impact on adolescent prevalence. College student use may increase under RCLs.
How They Did This
Narrative review of quasi-experimental studies examining how medical and recreational cannabis laws affect cannabis use and related substance use patterns.
Why This Research Matters
As cannabis legalization spreads globally, understanding its effects on population-level substance use is critical for policy design. This review highlights the importance of law specifics, not just legalization status.
The Bigger Picture
The heterogeneity of cannabis laws matters enormously. Lumping all "legalization" together obscures the fact that specific provisions (supply regulation, dispensary rules, advertising restrictions) drive different outcomes.
What This Study Doesn't Tell Us
Narrative review. Many studies treat MCLs or RCLs as binary when they vary significantly in implementation. Long-term effects of RCLs are largely unknown as most are recently enacted.
Questions This Raises
- ?Which specific policy provisions most affect cannabis use patterns?
- ?Will the long-term effects of recreational legalization differ from the early evidence?
- ?How should policymakers balance access with harm prevention?
Trust & Context
- Key Stat:
- MCLs increase adult use but not adolescent use
- Evidence Grade:
- Moderate: narrative review of quasi-experimental studies providing causal inference-informed evidence.
- Study Age:
- Published in 2019.
- Original Title:
- Early evidence of the impact of cannabis legalization on cannabis use, cannabis use disorder, and the use of other substances: Findings from state policy evaluations.
- Published In:
- The American journal of drug and alcohol abuse, 45(6), 644-663 (2019)
- Authors:
- Smart, Rosanna(5), Pacula, Rosalie Liccardo(18)
- Database ID:
- RTHC-02298
Evidence Hierarchy
Summarizes existing research on a topic.
What do these levels mean? →Frequently Asked Questions
Does legalization increase teen cannabis use?
Current evidence suggests neither medical nor recreational cannabis laws have significantly increased adolescent cannabis use prevalence, though this could change as markets mature and products diversify.
Why might supply regulation matter?
Laws with less regulated supply (more dispensaries, less oversight) appear to be associated with more adult cannabis use disorders, suggesting that market structure affects public health outcomes.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-02298APA
Smart, Rosanna; Pacula, Rosalie Liccardo. (2019). Early evidence of the impact of cannabis legalization on cannabis use, cannabis use disorder, and the use of other substances: Findings from state policy evaluations.. The American journal of drug and alcohol abuse, 45(6), 644-663. https://doi.org/10.1080/00952990.2019.1669626
MLA
Smart, Rosanna, et al. "Early evidence of the impact of cannabis legalization on cannabis use, cannabis use disorder, and the use of other substances: Findings from state policy evaluations.." The American journal of drug and alcohol abuse, 2019. https://doi.org/10.1080/00952990.2019.1669626
RethinkTHC
RethinkTHC Research Database. "Early evidence of the impact of cannabis legalization on can..." RTHC-02298. Retrieved from https://rethinkthc.com/research/smart-2019-early-evidence-of-the
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.