Randomised, blinded Phase I study (n=15) comparing low-dose (100 µg/kg) and high-dose (300 µg/kg) psilocybin to lorazepam (1 mg) in participants with moderate–severe OCD; dosing weekly with masked exposure across phases.
This two-phase, randomized study enrolls symptomatic OCD patients not taking psychoactive medications to evaluate safety, tolerability, and therapeutic effects of psilocybin versus lorazepam; all participants receive psilocybin at some point during participation in a blinded fashion.
Phase One is double-blind for participants and investigators; Phase Two is single-blind. Participants attend eight weekly dosing sessions (approximately 12 hours on-site per session); primary analyses compare low and high psilocybin doses and assess repeated-dose effects versus lorazepam.
Outcomes include symptom change, safety/tolerability, and mechanistic measures to explore how psilocybin alters brain activity relevant to OCD.
Psilocybin 100 µg/kg once per week for 8 weeks (blinded exposure across phases).
Psilocybin 300 µg/kg once per week for 8 weeks.
Lorazepam 1 mg once per week for 8 weeks used as an active comparator/masking agent.
Lorazepam 1 mg (Ativan) used as active comparator and masking agent.