First Randomized Trial Comparing Legal and Illegal Cannabis Markets

After 6 months, the legal cannabis group showed a trend toward lower cannabis misuse scores compared to the illegal market group (10.1 vs 10.9, p=0.052). Sub-group analysis revealed that the reduction was confined to legal access participants who also used other drugs. No significant changes were found for depression, anxiety, psychotic symptoms, or alcohol use.

Two-arm, parallel group, open-label randomized controlled trial in Basel, Switzerland. 374 adult cannabis users were randomized to receive legal cannabis through pharmacies (with safer use information and voluntary counseling) or to continue purchasing from the illegal market. Follow-up at 6 months.

This is the first randomized controlled trial directly comparing legal and illegal cannabis market effects on health outcomes. While observational studies of legalization exist, experimental evidence has been lacking.

This trial provides experimental evidence that regulated cannabis access, when combined with harm reduction measures, may reduce misuse. The finding that benefits concentrate among polysubstance users suggests that the regulated environment may be especially helpful for higher-risk individuals.

Open-label design means participants knew their group assignment. Conducted in one Swiss city with specific cultural and legal context. Six-month follow-up may be too short to detect longer-term effects. The primary outcome narrowly missed statistical significance.