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.
Cannabis policy researchers, legislators, public health officials, and advocacy organizations.
MCLs increase adult use but not adolescent use
What the researchers 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.
Why it 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 numbers in context
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 the study worked
Narrative review of quasi-experimental studies examining how medical and recreational cannabis laws affect cannabis use and related substance use patterns.
What this study cannot 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.
How to read the evidence
Moderate: narrative review of quasi-experimental studies providing causal inference-informed evidence.
When this study was published
Published in 2019.
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.
Questions still open
- 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?
Common questions
Does legalization increase teen cannabis use?
Why might supply regulation matter?
Read the original research
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
Citation
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