March 12, 2026
As states across the country consider psychedelic policy reform, new peer-reviewed research conducted by Denver Health’s Rocky Mountain Poison & Drug Safety (RMPDS) provides the most current evidence-based insights on how decriminalization has affected the use of psilocybin.
Appearing in the Journal of the American Medical Association (JAMA), the study is the first to show that recent increases in the use of psilocybin, commonly known as magic mushrooms, are independently linked to state policy changes. Rising reports of psychedelic use have coincided with both new decriminalization policies and a surge in cultural and media attention — making it difficult to know which was actually responsible for the increase. This study shows for the first time that decriminalization itself is driving the increase, separate from other trends.
RMPDS researchers used national survey data and applied advanced statistical methods to create a scenario of what would have happened in Colorado and Oregon without decriminalization but with the other potential factors still present. By comparing actual outcomes in these states with this “what-if” scenario, the team isolated the independent effect of policy change.
“This study answers the question policymakers actually face: How many additional people used a substance because the law changed?” said Joshua Black, PhD, MS, Senior Statistical Scientist at RMPDS. “Answering that question requires causal inference methodology, not just trend reporting.”
- In Oregon, decriminalization was associated with a 2.1-percentage-point increase in 12-month psilocybin use, representing between 70,000 and 90,000 additional people annually.
- In Colorado, use increased by 1.8 percentage points. The direction was similar, though not statistically significant due to a shorter post-policy observation period. This represents an estimated 85,000 to 110,000 additional people annually.
In Oregon, the estimated increase in overall use exceeded participation in regulated service systems. This finding suggests that a substantial portion of policy-attributable use occurred outside licensed clinical settings.
The research represents a significant methodological advancement in psychedelic policy evaluation. By accounting for demographic, socioeconomic and health-related factors, controlling for national trends and quantifying uncertainty, this approach produced evidence about the effects of psychedelic decriminalization for regulators, health agencies and legislators across drug classes.
As other states explore decriminalization or regulated access models for psychedelics, policymakers must weigh potential therapeutic benefits, such as treatment for severe mental health conditions, alongside public health risks, such as impaired cognition and cardiac concerns that may occur outside of clinical settings. This study demonstrates that rigorous, policy-attributable evaluation is feasible to guide responsible reform across drug classes, not just psychedelics.
“These findings underscore a critical reality for policymakers and public health leaders,” said Kate Reynolds, MPH, Director of Research at RMPDS. “As psychedelic policies evolve, the greatest public health impacts are likely happening outside regulated systems. RMPDS is uniquely positioned to help governments understand and anticipate those impacts with independent, data-driven evidence.”
