Background: Only one open-label psilocybin trial has been published to date on OCD (Moreno et al., 2006). We present results from a single-site study investigating the safety and clinical effects of psilocybin on OCD with a randomized (1:1), double-blind, placebo-controlled design.

Methods: We compared single-dose psilocybin (0.25 mg/kg) vs. active placebo (250 mg niacin) in this trial. Non-directive psychological support was provided by trained facilitator pairs during preparatory, dosing, and integration visits. We recruited 26 adult participants with a primary diagnosis of OCD, a Y-BOCS score of at least 19, and failure of at least one trial of standard-of-care treatment for OCD. Efficacy was evaluated on the AY-BOCS and self-reported VAS at the primary endpoint of 48 hours post-dosing, and other measures up to 12-week follow-up. Safety was assessed by monitoring AEs, C-SSRS, vitals, SUDs, and medication changes. Twelve completers completed a qualitative interview assessing pre-dosing, dosing, and post-dosing experiences, and the data was analyzed via interpretative phenomenological analysis (IPA).

Results: Enrollment is nearly complete, and final results will be presented at the conference. Preliminary results are encouraging; current completers tend to report rapid and clinically significant reductions in OCD symptoms at primary endpoint, with a good safety profile. IPA also yielded various themes linking acute and post-dosing effects, revealing possible psychological mechanisms underlying psilocybin’s efficacy in treating OCD.

Conclusion: Psilocybin combined with non-directive psychological support is currently being investigated as an intervention for OCD in a rigorous, controlled trial, with promising preliminary results.