Psilocybin Use Rose in Oregon and Colorado After Decriminalization, JAMA Study Finds
When Oregon decriminalized psilocybin in 2020 and Colorado followed in 2022, proponents argued the moves would bring therapeutic access to people suffering from depression, PTSD, and addiction. Critics warned that loosening restrictions would simply increase recreational use. A new study published in JAMA offers the first real numbers to inform that debate.
The research, led by Joshua C. Black, PhD, at the Rocky Mountain Poison and Drug Safety center, estimated changes in 12-month psilocybin use associated with decriminalization in both states. The findings come at a time when several other states and cities are considering similar policy changes, making the data particularly relevant for legislators and public health officials weighing the evidence.
Tracking use after the policy shift
Psilocybin - the psychoactive compound found in certain mushroom species - has attracted intense scientific interest in recent years. Clinical trials have shown promising results for treatment-resistant depression, end-of-life anxiety, and substance use disorders. Oregon established a regulated therapeutic framework alongside decriminalization, while Colorado created a more limited system focused on supervised use at licensed healing centers.
But clinical trials operate under controlled conditions with carefully screened participants. The question these policies raise is different: what happens to population-level use patterns when a previously illegal substance becomes decriminalized?
The JAMA study used population survey data to estimate changes in self-reported 12-month psilocybin use, comparing trends before and after decriminalization in both states. The specific methodology, effect sizes, and comparison with control states are detailed in the full paper (DOI: 10.1001/jama.2026.1952).
Policy context matters
Oregon and Colorado took meaningfully different approaches. Oregon's Measure 109 created a licensed psilocybin services framework allowing supervised therapeutic sessions, while also decriminalizing personal possession through a separate measure. Colorado's Proposition 122 decriminalized personal use and possession for adults 21 and older while establishing a framework for regulated healing centers.
These differences in regulatory structure may influence use patterns in distinct ways - a nuance that single-number headlines can easily miss. Whether increased use primarily reflects therapeutic applications, supervised sessions, or unsupervised recreational consumption has very different public health implications.
What the data cannot tell us
This study provides population-level estimates, but several important questions remain beyond its scope. Survey-based measures of drug use rely on self-report, which may be affected by changes in social desirability - people may be more willing to report using a substance once it is no longer criminal, regardless of whether their actual use changed.
The study also cannot distinguish between therapeutic and recreational use, between supervised and unsupervised consumption, or between people using psilocybin for the first time and those who previously used it but would not have reported it when the substance was criminalized. These distinctions are critical for evaluating whether decriminalization is achieving its intended goals.
Both states decriminalized psilocybin relatively recently, meaning the data capture only early trends. Longer-term patterns may look quite different as regulatory frameworks mature, therapeutic infrastructure develops, and cultural norms around psychedelic use continue to evolve.
For states considering similar legislation, this study provides a useful baseline - but only a baseline. The harder questions about clinical outcomes, adverse events, and whether regulated access genuinely improves mental health at the population level will require different kinds of studies and considerably more time.