A Randomized Double-masked Dose-controlled Trial to Assess the Tolerability, Safety, Subjective Experience, and Efficacy of Repeated Administration of Three Different Doses of Psilocybin Whole Mushroom for the Treatment of Obsessive-compulsive Disorder.

The study tries to improve our treatments for people who have obsessive-compulsive disorder (OCD) by testing psilocybin, a mind altering drug that changes activity in brain areas involved in OCD. 30 patients with moderate or more severe OCD who are not taking mind altering medications or street drugs will participate in a 12 week study. Participants will be assigned (by luck of the draw) to take a low, medium, or high dose whole psilocybin mushroom contained in three chocolate pieces, prepared for this study by the Scottsdale Research Institute. Participants will come to the University of Arizona CATS Research Unit in Tucson for assessment, if they are found to be fit for study participation, they will be scheduled for a preparation session with a study therapist and then will participate in a dosing session when they will ingest three pieces of chocolate containing psilocybin mushroom. They will answer questions of how they are feeling, and will be monitored for safety by two study staff members, and their vital signs will be checked every hour on the day they receive the study drug. The will be sent home with a responsible adult selected by the patient after they are felt to be safe once the effects of the drug have resolved. Participants will receive four different doses separated by about three weeks. After they complete the treatment phase, they will be contacted monthly for follow up assessment of efficacy, and safety.