Two doses of psilocybin, given alongside psychotherapy, substantially reduced heavy drinking in people with alcohol use disorder compared to an active placebo (diphenhydramine) plus psychotherapy. Over 32 weeks, heavy drinking days averaged 9.7% in the psilocybin group versus 23.6% in the placebo group—a mean difference of 13.9 percentage points. Daily alcohol consumption was also lower with psilocybin. No serious adverse events occurred in the psilocybin group. The findings support further research into psilocybin-assisted treatment for alcohol use disorder.
Classic psychedelics like psilocybin may help people change their behavior in substance use disorders. This paper describes the protocol for a multi-site, double-blind, randomized controlled trial that tested psilocybin-assisted psychotherapy in 96 alcohol-dependent volunteers. Participants received either psilocybin or an active placebo (diphenhydramine) during two dosing sessions, alongside a structured 12-week psychotherapy platform. The primary outcome was the proportion of heavy drinking days over 32 weeks after the first dose. Secondary outcomes included safety, abstinence, craving, and self-efficacy. The primary results are reported elsewhere; this paper focuses on the rationale and design decisions.