Therapy and psilocybin for severe obsessive-compulsive disorder

Plain-English translation of NCT04882839 on ClinicalTrials.gov ↗ · Source last updated November 2025 · Translation generated July 2026 · How we translate trials

Phase 2 — Testing in a bigger group (up to a few hundred people) to see if the treatment actually works and is still safe.

What is this trial?

This trial is testing psilocybin—a naturally occurring compound—combined with professional psychotherapy to treat severe obsessive-compulsive disorder (OCD) in people who haven't benefited from standard medications or therapy. The study will carefully monitor whether this medication, given in a controlled setting with trained therapists present, is safe and can reduce the distressing thoughts and repetitive behaviors that define OCD. Researchers hope this approach might help people whose symptoms have persisted despite other treatments.

Most people with OCD improve with standard treatments like SSRIs and cognitive behavioral therapy, but about 25% don't respond at all, and 40–60% see their symptoms return. This trial exists to explore whether the medication could offer relief for these patients who have exhausted conventional options and may be at risk of turning to more invasive interventions.

Do you qualify?

You likely qualify if…

you have been diagnosed with obsessive-compulsive disorder by a trained clinician
your OCD symptoms are severe enough to significantly impact your daily life
you have tried and failed at least one standard medication or therapy for OCD
you are between 18 and 65 years old
you have been off SSRI medications for at least five half-lives of the drug plus 2 weeks
you are willing to commit fully to therapy sessions, medication dosing, and follow-up visits

You likely don't qualify if…

you have a personal or close family history of schizophrenia, bipolar disorder, or other psychotic disorders
you have struggled with substance abuse in the past 12 months
you have current suicidal thoughts or have attempted suicide in the past 12 months
you are pregnant or planning to become pregnant during the study
you have used any psychedelic drugs in the past 12 months

What participation looks like

You would attend multiple therapy sessions with trained psychotherapists and participate in carefully supervised sessions where you receive the medication in a clinical setting. Between sessions, you'll work with your therapist on psychological strategies to manage your OCD. The study involves regular check-ins and assessments to measure whether your symptoms improve. You would need to avoid other psychiatric medications and recreational drugs during the study period and maintain contact with the research team throughout.

Therapy and psilocybin for severe obsessive-compulsive disorder

What is this trial?

Do you qualify?

What participation looks like

Trial locations(1 site)