About the study
This trial asked two questions at once: whether a single dose of psilocybin reduces OCD symptoms more than an active placebo, and what happens in the brain when it does.
Participants with OCD who had not responded adequately to standard treatment were randomized, double-blind, to 0.25 mg/kg psilocybin or 250 mg niacin — an active comparator chosen because it produces noticeable physical sensations without psychedelic effects, making the blind harder to break. Dosing took place during an inpatient admission of at least three nights, with preparatory and follow-up sessions around it. Resting-state fMRI before dosing and again 48 hours after tested the hypothesis that psilocybin normalizes fronto-striatal connectivity, and that the degree of normalization tracks symptom improvement. Symptoms were assessed to three months. Participants who received niacin were offered open-label psilocybin afterward.
Enrollment for this study is closed.
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 21 to 65
- Primary DSM-5 diagnosis of OCD with a Y-BOCS score of 19 or greater
- At least one prior failed trial of standard OCD treatment, medication or CBT/ERP
- Off SSRIs for at least eight weeks before randomization, and willing to refrain from psychiatric medication through the study period
- Willing to complete an inpatient stay, neuroimaging, and all assessments
- An emergency contact able to transport the participant home at the end of the dosing week
What ruled someone out
- Personal or immediate family history of a schizophrenia spectrum or other psychotic disorder, bipolar I or II, or major depression with psychotic features
- Active suicidal intent
- Unremitted Tourette syndrome, autism spectrum disorder, OCPD, or BPD
- Current substance use disorder other than mild alcohol use disorder
- Unstable neurological or medical conditions, including poorly managed diabetes, hypertension, cardiovascular disease, seizures, or chronic or severe headaches
- Head injury with loss of consciousness beyond 30 minutes
- Any contraindication to MRI, including metal implants or fragments
- Psychedelic use within the prior twelve months
Study team
Study facts
Phase 1 · Randomized, double-blind, active-placebo-controlled · Enrollment 31 · Sponsor: Yale University, with the Heffter Research Institute and NIMH · Site: Connecticut Mental Health Center, New Haven · PI: Benjamin Kelmendi, M.D.
Contact & location
Completed
Data collection is complete. 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: Psilocybin Treatment in Obsessive-Compulsive Disorder: a Preliminary Efficacy Study and Exploratory Investigation of Neural Correlates. View NCT03356483 on ClinicalTrials.gov (opens in a new tab)