What Happens When Countries Regulate Cannabis: Arrests Drop, Adult Use Rises | Research

The takeaway

A systematic review across five jurisdictions found that regulated cannabis supply consistently decreased cannabis arrests and increased adult use, while negative health outcomes were most pronounced in US states.

Cannabis policy researchers, legislators, public health officials, international drug policy advocates

Adult use increased across all jurisdictions; adolescent use did not

What the researchers found

Across the Netherlands, Spain, US legalization states, Uruguay, and Canada, consistent outcomes included decreased cannabis-related arrests, increased adult (but not adolescent) cannabis use, and increased healthcare utilization (not traffic-related). Negative health outcomes were most concentrated in US states. Evidence was limited for non-US jurisdictions.

Why it matters

With more countries considering cannabis regulation, comparing outcomes across different models helps identify which approaches minimize harms while achieving social benefits like reduced criminalization.

The numbers in context

Five jurisdictions compared. Consistent outcomes: decreased arrests, increased adult use (not adolescent), increased non-traffic healthcare utilization. US states showed most negative health outcomes. Other jurisdictions had limited study designs or timeframes.

How the study worked

Three-level systematic literature review assessing nine indicators across three domains (social, cannabis use, health-related) in five jurisdictions with different regulation models. Prioritized quasi-experimental studies and categorized by study design and outcome direction.

What this study cannot tell us

Heterogeneity in regulation models makes direct comparison difficult. US states dominate the evidence base. Non-US jurisdictions had fewer rigorous studies and shorter follow-up periods. Could not fully distinguish between regulation model effects and other country-specific factors.

How to read the evidence

Strong: systematic review across multiple jurisdictions prioritizing quasi-experimental evidence, though limited by heterogeneity in regulation models and evidence quality

When this study was published

Published in 2025

The bigger picture

No single regulation model achieves all desired outcomes. The variation in results across jurisdictions suggests that the specific design of cannabis regulation matters significantly for public health outcomes.

Questions still open

Which specific regulatory features drive the different outcomes? Can countries design hybrid models that capture benefits while minimizing harms? Why do US states show more negative health outcomes?

Common questions

Does cannabis legalization increase teen use?

Across all five jurisdictions reviewed (Netherlands, Spain, US, Uruguay, Canada), regulated cannabis supply was associated with increased adult use but not adolescent use. This is one of the more consistent findings across different regulation models.

Which regulation model works best?

No single model emerged as clearly superior. The review found that different models have different trade-offs. The authors suggest jurisdictions may need to mix elements from different approaches to achieve the best balance of benefits and harms.

Read the original research

Getting "The whole picture": A review of international research on the outcomes of regulated cannabis supply.

The International journal on drug policy, 142, 104796

View on PubMed ↗Publisher’s paper ↗

Citation

Belackova, Vendula; Petruzelka, Benjamin; Cihak, Jakub; Michailidu, Jana; Mravcik, Viktor. (2025). Getting "The whole picture": A review of international research on the outcomes of regulated cannabis supply.. The International journal on drug policy, 142, 104796. https://doi.org/10.1016/j.drugpo.2025.104796