About the study
Nearly every psilocybin trial in OCD has tested a single dose. This one tests two, asking whether repeated dosing produces greater symptom reduction than a single administration — and whether the psychological mechanisms often invoked to explain psilocybin's effects actually mediate improvement.
Participants are randomized to immediate treatment or to a waitlist with treatment delayed seven weeks. The first dose is fixed at 25 mg. The second, given a week later, is either the same or increased to 30 mg depending on response measured four days after the first. Ratings are made by independent assessors blinded to condition. The study runs entirely on an outpatient basis, with dosing sessions occupying a full day and follow-up extending to twelve months.
Enrollment for this study is closed. People interested in OCD research can ask to be notified about future studies.
Is this study a fit?
The study team makes the final decision after screening. Final eligibility is determined in clinical screening, never by this page.
Who was eligible
- Adults 18 to 65
- Primary DSM-5 diagnosis of OCD with a Y-BOCS-II score of 26 or greater
- At least one prior failed trial of standard OCD treatment, medication or therapy
- Off psychotropic medication for OCD or comorbid conditions for at least eight weeks before randomization, and not in current CBT or ERP
- An adult emergency contact able to provide transport and comment on changes in mood or behavior
- Willing to sign a medical release and adhere to lifestyle and medication restrictions
What ruled someone out
- Personal or first-degree family history of schizophrenia, another psychotic disorder, or bipolar I/II — or no knowledge of biological family history
- Active suicidal intent, or suicidal or self-injurious behavior
- Unremitted Tourette syndrome, or a lifetime diagnosis of autism spectrum disorder
- Current substance use disorder other than mild alcohol use disorder
- Any neurological condition, including seizures or chronic or severe headaches
- Head injury with loss of consciousness beyond 30 minutes
- Classic psychedelic use within the prior twelve months
- Tobacco or THC use more than twice weekly on average over the prior 30 days
- Medical conditions making study procedures unsafe, including hypertension, cardiovascular disease, moderate-to-severe hepatic or renal impairment, diabetes, or thyroid disease
Study team
Study facts
Phase 1 · Randomized, waitlist-controlled, blinded independent ratings · Target enrollment 28 · Sponsor: Yale University, with the Steven & Alexandra Cohen Foundation · Sites: ENACT (40 Temple St.) and the Yale Program for Psychedelic Research, New Haven · PI: Benjamin Kelmendi, M.D. · Co-I Terence Ching, Ph.D.
Contact & location
No longer recruiting
This study is no longer recruiting. Follow-up, data collection, or analysis is ongoing. There is no application on this page. Other ENACT studies are actively recruiting.
Contact the study team
- Phone
- (203) 444-1795
- Location
- Enact Research Collaborative
40 Temple St., 4th Floor, Suite 4C
New Haven, CT 06510
Registry title: Effects of Repeated Dosing of Psilocybin on Obsessive-Compulsive Disorder: A Randomized, Waitlist-Controlled Study. View NCT05370911 on ClinicalTrials.gov (opens in a new tab)