Psilocybin Whole Mushroom for the Treatment of Obsessive-compulsive Disorder.

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.