NCT05370911

Effects of Repeated Dosing of Psilocybin on Obsessive-Compulsive Disorder: A Randomized, Waitlist-Controlled Study

Active, enrolled Phase 1 Last updated 2 June 2026

What this trial tests

Phase 1 trial testing Psilocybin in Obsessive-Compulsive Disorder in 28 participants. Participants enrolled and being followed up; not accepting new ones.

Timeline

20 July 2023

Primary endpoint
17 February 2026

1 February 2027

Quick facts

Lead sponsor	Yale University
Phase	Phase 1
Status	Active, enrolled
Study type	INTERVENTIONAL
Allocation	randomized
Design	parallel
Masking	single
Primary purpose	treatment
Enrollment	28
Start date	20 July 2023
Primary completion	17 February 2026
Estimated completion	1 February 2027
Sites	2 locations across United States

Drugs / interventions tested

• Psilocybin — full drug profile →

Conditions studied

• Obsessive-Compulsive Disorder — all drugs for Obsessive-Compulsive Disorder →

Sponsor

Yale University

Who can join

Adults 18 to 65, any sex, with Obsessive-Compulsive Disorder. Patients with the condition only — healthy volunteers not accepted.

What's being measured

Primary outcomes are the specific endpoints the trial is designed to prove or disprove.

• Change in Yale-Brown Obsessive-Compulsive Scale-Second Edition (Y-BOCS-II) Severity Scale total score from baseline at 4 days post-second dose
  Time frame: Baseline & 4 days post-second dose
  Clinician-administered assessment of severity of OCD symptoms over the past seven days. The most prominent obsessions and compulsions are rated on the Severity Scale from 0 to 4. Total Y-BOCS-II scores range from 0 to 40, with higher scores indicating greater severity of OCD symptoms.

Sponsor's own description

This study aims to investigate the effects of repeated dosing of oral psilocybin on obsessive-compulsive disorder (OCD) symptomatology in a randomized, waitlist-controlled design with blinded independent ratings, and assess psychological mechanisms that may mediate psilocybin's therapeutic effects on OCD.

Publications & conference data

8 peer-reviewed publications reference this trial (live from Europe PMC):

1. Psychedelic therapies reconsidered: compounds, clinical indications, and cautious optimism.
   Mitchell JM, Anderson BT. · · 2024 · cited 32× · PMID 37479859 · DOI 10.1038/s41386-023-01656-7
2. Psychedelics for the Treatment of Obsessive-Compulsive Disorder: Efficacy and Proposed Mechanisms.
   Collins HM. · · 2024 · cited 8× · PMID 39611453 · DOI 10.1093/ijnp/pyae057
3. Safety, feasibility, tolerability, and clinical effects of repeated psilocybin dosing combined with non-directive support in the treatment of obsessive-compulsive disorder: protocol for a randomized, waitlist-controlled trial with blinded ratings.
   Ching THW, Amoroso L, Bohner C, D'Amico E, et al · · 2023 · cited 5× · PMID 38264632 · DOI 10.3389/fpsyt.2023.1278823
4. Hereditary Patterns and Genetic Associations in Obsessive-Compulsive Disorder (OCD): Neuropsychiatric Insights, Genetic Influences, and Treatment Perspectives.
   Dhiman A, Mehan S, Khan Z, Tiwari A, et al · · 2025 · cited 4× · PMID 39219434 · DOI 10.2174/0115665232316708240828063527
5. Artificial Intelligence in Obsessive-Compulsive Disorder: A Systematic Review.
   Kim J, Pacheco JPG, Golden A, Aboujaoude E, et al · · 2025 · cited 2× · PMID 40524733 · DOI 10.1007/s40501-025-00359-8
6. Psilocybin in pharmacotherapy of obsessive-compulsive disorder.
   Owe-Larsson M, Kamińska K, Buchalska B, Mirowska-Guzel D, et al · · 2024 · cited 1× · PMID 39088105 · DOI 10.1007/s43440-024-00633-1
7. Mechanisms of therapeutic change after psychedelic treatment in OCD.
   Maloney G, Ching T, Kichuk SA, Pittenger C, et al · · 2024 · cited 1× · PMID 38615521 · DOI 10.1016/j.psychres.2024.115907
8. Yale Program for Psychedelic Science (YPPS) Manual for Psilocybin Combined with Non-Directive Support in the Treatment of OCD
   Ching THW, Grazioplene R, Pittenger C, Kelmendi B. · · 2023 · DOI 10.31234/osf.io/ba42z