Obsessive-Compulsive DisorderPhase 1NCT05370911
Effects of Repeated Psilocybin Dosing in OCD
A Phase 1 study testing Psilocybin in people with Obsessive-Compulsive Disorder, run by Yale University at 2 sites in United States.
Trial summary
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. Read more about this study
- Who is it for?
- Ages 18 to 65 years
- Conditions the study is for
- Obsessive-Compulsive Disorder
- What is being tested?
- Psilocybin
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 28 participants
- Where
- 2 sitesUnited States
- Study dates
- 20 Jul 2023to Feb 2027
- Phase
- Phase 1
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 65 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Primary DSM-5 diagnosis of OCD, with Y-BOCS-II score of 26 or greater at screening
- Failed at least one medication and/or therapy trial of standard care treatment for OCD
- English fluency
- Agree to sign a medical release for investigators to communicate directly with participants' providers to confirm medication and psychotherapy histories or arrange contingencies in event of crises.
- Agree to provide an adult contact (relative, spouse, close friend or other caregiver) who is willing and able to be reached by the PI and/or study personnel in the event of an emergency, and who can provide transportation for study visits and independently comment on any changes in the participant's mood or behavior after each administration of psilocybin.
- Agree to commit to all study procedures.
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- Ability to orally ingest pills for psilocybin dosing visits.
- Agree to adhere to lifestyle and medication modifications.
- Must not be on psychotropic medications for OCD or comorbid psychiatric conditions for at least 8 weeks at the time of randomization, and agree to refrain from taking or starting any psychiatric medications until after 4 weeks post-second dose.
- Must not be in current psychotherapy (CBT or ERP) and must not start new course of psychotherapy (CBT or ERP) for OCD or comorbid psychiatric conditions until after 4 weeks post-second dose.
- If participant is of childbearing potential, must have a negative pregnancy test at study entry and prior to each dosing session.
- If participant is of childbearing potential, agree to use adequate birth control and not attempt to become pregnant during study up to 4 weeks post-second dose.
Who cannot join
- Personal or immediate (first-degree relative) family history of formally diagnosed schizophrenia or other psychotic disorders, or bipolar I/II disorder
- Lack of knowledge about biological families' medical history, due to adoption or other circumstance
- Active suicidal intent or suicidal or non-suicidal self-injurious behaviors
- Unremitted Tourette syndrome
- Lifetime diagnosis of autism spectrum disorder
- Current substance use disorder (except for mild alcohol use disorder)
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- Any neurological condition, including history of seizure(s) or chronic/severe headaches
- Any history of head injury with loss of consciousness for more than 30 min
- Any use of classic psychedelic substances within the prior 12 months
- Unwillingness to abstain from use of classic psychedelics outside of the study up to 4 weeks post-second dose.
- Use of tobacco products or a THC-containing product more than 2 times per week on average over the past 30 days at screening.
- Unwilingness or inability to abstain from use of tobacco or THC-containing products from 1 week prior to randomization up to 4 weeks post-second dose.
- Positive urine drug test for any prohibited substance at screening or days of dosing, or positive breathalyzer test for alcohol on days of dosing
- Unwillingness or inability to abstain from alcohol use at least 24 hours prior to the days of dosing, up to 24 hours after each dosing day (or corresponding intervals for waitlist group).
- Any medical conditions that may render study procedures unsafe, including hypertension, history of cardiovascular disease, moderate-to-severe hepatic or renal impairment, diabetes, and hypo- or hyperthyroidism.
Trial locations and contacts
2 sites in 1 country.
United States2 sites
Enact Research Collaborative (40 Temple St, 4th Floor)
New Haven, Connecticut, 06510
Yale Program for Psychedelic Research
New Haven, Connecticut, 06510
About this study
Official title: Effects of Repeated Dosing of Psilocybin on Obsessive-Compulsive Disorder: A Randomized, Waitlist-Controlled Study
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.
Read the detailed description
Aim 1: To examine the effects of two doses of psilocybin on OCD symptoms among participants in the immediate treatment condition, compared to participants in the waitlist control/delayed treatment condition. The investigators hypothesize that participants in the immediate treatment group will report statistically significantly greater symptom improvement from baseline 4 days post-second dose, compared to participants in the waitlist control/delayed treatment group at the same interval during their waitlist phase.
Aim 2: To examine the effects of two doses of psilocybin on OCD symptoms, compared to one dose. The investigators hypothesize that two doses of oral psilocybin will reduce OCD symptoms to a statistically significantly greater extent than one dose.
This study aims to investigate the effects of repeated dosing of oral psilocybin on OCD symptomatology and assess psychological mechanisms that may mediate psilocybin's therapeutic effects on OCD. This study will employ a randomized, waitlist-controlled design with blinded independent ratings, with participants randomized to receive either immediate treatment (two doses oral psilocybin separated by one week) or delayed treatment (7 weeks post-randomization). An adaptive dose selection strategy will be implemented, with the first dose being standardized at 25 mg of psilocybin, and the second dose being either the same or a higher dosage (i.e., 30 mg) on the basis of a clinically significant response from baseline or not, respectively, 4 days post-first dose.
This study is conducted entirely on an outpatient basis with the possibility of remote/virtual follow-up visits after each dosing session. The dosing sessions last the entire day, and participants will be medically cleared prior to being permitted to return home with assistance (e.g., driven by a family member or friend, or ride share).
- Conditions
- Obsessive-Compulsive Disorder
- Being tested
- Psilocybin
- Keywords
- Psilocybin
- Medical subject headings
- Obsessive-Compulsive Disorder
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
PsilocybinDrug
The first oral dose will be 25 mg, and the second dose will be either 25 mg or 30 mg, depending on response to first dose.
Psilocybin is a naturally occurring hallucinogenic ingredient found in some varieties of mushrooms that can be produced synthetically. It is considered to be a serotonergic psychedelic. We will use synthetically produced oral psilocybin in this study.
Other Names:
"Magic Mushrooms"
| Study group | Role | What they receive |
|---|---|---|
| Immediate Treatment | Experimental | Participants randomized to this condition will receive treatment immediately, facilitated by two study staff members, and which consists of two preparatory sessions, followed by the first dosing session and two integration sessions, then the second dosing session and two integration sessions. This is followed by follow-up and long-term follow-up visits up to 12 months post-second dose. Receives: Drug: Psilocybin |
| Waitlist Control/Delayed Treatment | No intervention | Participants randomized to this condition will first enter a waitlist phase that lasts for 7 weeks, after which rater unblinding will occur, and participants will be rescreened. If participants remain eligible at this time, they will begin their treatment phase. During their treatment phase, participants in this condition will receive the same treatment as described for participants in the immediate treatment group. This is followed by follow-up and long-term follow-up visits up to 12 months post-second dose. |
What is being measured
The primary outcome is the main question the study is designed to answer.
Change in Yale-Brown Obsessive-Compulsive Scale-Second Edition (Y-BOCS-II) Severity Scale total score from baseline at 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.
Measured: Baseline & 4 days post-second dose
Secondary outcomes (29)
Change in Montgomery-Asberg Depression Scale (MADRS) total score from baseline at 4 days post-second dose
Clinician-administered assessment of severity of depressive symptoms over past month. Total scores range from 0 to 60, with higher scores indicating greater severity of depressive symptoms.
Measured: Baseline & 4 days post-second dose
Change in Dimensional Obsessive-Compulsive Scale (DOCS) total score from baseline at 4 days post-second dose
Self-report measure of various OCD symptoms over the modified time frame of the past week. Total scores range from 0 to 140, with higher scores indicating greater severity of OCD symptoms.
Measured: Baseline & 4 days post-second dose
Change in Obsessive Beliefs Questionnaire-44 (OBQ-44) total score from baseline at 4 days post-second dose
Self-report measure of various obsessive beliefs implicated in OCD in general. Total scores range from 44 to 308, with higher scores indicating greater severity of obsessive beliefs.
Measured: Baseline & 4 days post-second dose
Change in Acceptance and Action Questionnaire for Obsessions and Compulsions (AAQ-OC) total score from baseline at 4 days post-second dose
Self-report measure of experiential avoidance and psychological flexibility in the context of OCD symptoms in general. Total scores range from 13 to 91, with higher scores indicating greater psychological inflexibility.
Measured: Baseline & 4 days post-second dose
Change in Tolerance of Uncontrollability Questionnaire (TOUQ) total score from baseline at 4 days post-second dose
Self-report measure of ability to tolerate uncontrollability (or inversely need for control) in general. Total scores range from 19 to 133, with higher scores indicating greater tolerance of uncontrollability.
Measured: Baseline & 4 days post-second dose
Change in White Bear Suppression Inventory (WBSI) total score from baseline at 4 days post-second dose
Self-report measure of thought suppression tendencies in general. Total scores range from 15 to 75, with higher scores indicating stronger thought suppression tendencies.
Measured: Baseline & 4 days post-second dose
Change in Difficulties in Emotion Regulation Scale (DERS) total score from baseline at 4 days post-second dose
Self-report measure of emotion regulation difficulties in general. Total scores range from 36 to 180, with higher scores indicating greater difficulties with regulating emotions.
Measured: Baseline & 4 days post-second dose
Change in Southampton Mindfulness Questionnaire (SMQ) total score from baseline at 4 days post-second dose
Self-report measure of trait mindfulness in regards to distressing thoughts and images. Total scores range from 0 to 96, with higher scores indicating greater trait mindfulness.
Measured: Baseline & 4 days post-second dose
Toronto Mindfulness Scale (TMS)
Self-report measure of state mindfulness during dosing session. Total scores range from 0 to 52, with higher scores indicating greater state mindfulness.
Measured: Up to 3 weeks for immediate treatment condition, and up to 10 weeks for waitlist condition
Set, Setting, and Intentions (SSI) Scale
Self-report measure of set, setting, and clarity of intentions just prior to dosing session. Total mean scores range from 0 to 100 (after reverse-scoring two items), with higher scores indicating greater preparedness for the dosing session.
Measured: Up to 3 weeks for immediate treatment condition, and up to 10 weeks for waitlist condition
Mystical Experience Questionnaire (MEQ)
Self-report measure of acute mystical experiences during dosing. Total mean scores range from 0 to 5, with higher scores indicating greater mystical experiences.
Measured: Up to 3 weeks for immediate treatment condition, and up to 10 weeks for waitlist condition
Psychological Insight Questionnaire (PIQ)
Self-report measure of acute psychological insights during dosing. Total mean scores range from 0 to 5, with higher scores indicating greater insightful experiences.
Measured: Up to 3 weeks for immediate treatment condition, and up to 10 weeks for waitlist condition
Challenging Experience Questionnaire (CEQ)
Self-report measure of acute challenging experiences during dosing. Total mean transformed scores range from 0 to 1, with higher scores indicating greater challenging experiences.
Measured: Up to 3 weeks for immediate treatment condition, and up to 10 weeks for waitlist condition
Ego Dissolution Inventory (EDI)
Self-report measure of acute experiences of ego dissolution during dosing. Total mean scores range from 0 to 100, with higher scores indicating greater ego dissolution.
Measured: Up to 3 weeks for immediate treatment condition, and up to 10 weeks for waitlist condition
Emotional Breakthrough Inventory (EBI)
Self-report measure of different experiences of emotional breakthroughs during dosing. Total mean scores range from 0 to 100, with higher scores indicating greater emotional breakthrough.
Measured: Up to 3 weeks for immediate treatment condition, and up to 10 weeks for waitlist condition
Change in Self-Compassion Scale (SCS) total mean score from baseline at 4 days post-second dose
Self-report measure of self-compassion in general. Total mean scores range from 1 to 5 (after reverse-scoring 13 items), with higher scores indicating greater self-compassion.
Measured: Baseline & 4 days post-second dose
Change in Ten-Item Personality Inventory (TIPI) total score from baseline at 4 days post-second dose
Brief self-report measure of Big Five personality dimensions. Total scores range from 10 to 70 (after reverse-scoring 5 items), with higher scores indicating more positive personality traits.
Measured: Screening, 4 days and 12 months post-second dose
Change in Persisting Effects Questionnaire (PEQ) subscale scores from 4 weeks post-second dose at 12 months post-second dose
Self-report measure of persisting effects from dosing in general. Subscale scores range from a minimum of 0 to a maximum of 5 to 85, with higher scores indicating greater positive or negative persisting changes since dosing.
Measured: 4 weeks post-second dose & 12 months post-second dose
Change in Alcohol Use Disorders Identification Test (AUDIT) total score from baseline at 4 weeks post-second dose
Self-report measure of alcohol use severity. Total scores range from 0 to 40, with higher scores indicating greater alcohol use severity.
Measured: Baseline & 4 weeks post-second dose
Change in Drug Use Disorders Identification Test (DUDIT) total score from baseline at 4 weeks post-second dose
Self-report measure of illicit substance use. Total scores range from 0 to 44, with higher scores indicating greater illicit substance use severity.
Measured: Baseline & 4 weeks post-second dose
Change in Fagerstrom Test for Nicotine Dependence (FTND) total score from baseline at 4 weeks post-second dose
Self-report measure of nicotine use. Total scores range from 0 to 10, with higher scores indicating greater nicotine use severity.
Measured: Baseline & 4 weeks post-second dose
Change in World Health Organization Disability Assessment Scale, v2.0 (WHODAS-2.0) 12-item, self-administered version total score from baseline at 4 days post-second dose
Self-report measure of symptom-related functional impairment in general. Total scores range from 12 to 60, with higher scores indicating greater functional impairment.
Measured: Baseline & 4 weeks post-second dose
Change in Quality of Life Enjoyment & Satisfaction Questionnaire - Short Form (Q-LES-Q-SF) percentage maximum score from baseline at 4 days post-second dose
Self-report measure of life satisfaction over the past week. Percentage maximum scores range from 0% to 100%, with higher percentages indicating greater life satisfaction.
Measured: Baseline & 4 weeks post-second dose
Writing task
Online writing task in which participants describe their perceptions of their OCD symptoms with a short written essay
Measured: Baseline & 4 days post-second dose
Columbia Suicide Severity and Risk Scale (C-SSRS) Since Last Visit version
Clinician-administered assessment of suicidal ideation and behaviors since the last study visit
Measured: Every study visit through study completion, an average of 12 months and 3 weeks for immediate treatment condition, and an average of 12 months and 10 weeks for waitlist condition
Theoretical Orientation Profile Scale-Revised (TOPS-R)
Clinician-reported measure of theoretical orientation over 11 subscales, each corresponding to a different theoretical orientation. Subscale scores range from 1 to 30, with higher scores indicating greater affiliation with a particular theoretical orientation.
Measured: Baseline
Working Alliance Inventory-Short Revised (WAI-SR)
Self-report measure of perceived working alliance with study clinicians. Total scores range from 0 to 60, with higher scores indicating stronger perceived working alliance.
Measured: Up to 4 days post-second dose
Change in Symptom Provocation Task (SPT) ratings from baseline at 4 days post-second dose
Behavioral measure of OCD symptoms when provoked with idiosyncratic questions. Scores for compulsive urges range from 0-10 in terms of VAS ratings, with higher VAS ratings indicating greater compulsive urges.
Measured: Baseline & 4 days post-second dose
Stanford Expectations of Treatment Scale (SETS)
Self-report measure of treatment expectancy over 2 subscales, corresponding to positive and negative expectancy. Subscale scores range from 7 to 21, with higher scores indicating more positive or negative expectancy.
Measured: Baseline
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted12 May 2022
- Study start20 Jul 2023
- Primary completion17 Feb 2026
- Study completionFeb 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (5)Papers the sponsor has linked to this study.
- Other trials for Obsessive-Compulsive DisorderStudies of the same condition, open and under way.
- More trials run by Yale UniversityThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 1
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- In the study, participants will be randomized to receive either immediate treatment with two doses of oral psilocybin separated by one week (n = 15) or enter a waitlist control/delayed treatment group and receive the same treatment 7 weeks post-randomization (n = 15).
- Masking
- Single blind
- Who is masked
- Outcomes assessor
- Enrolment
- 28 participants (actual)
Sponsor and investigators
- Lead sponsor
- Yale University
- Sponsor type
- University, hospital or other
- Collaborators
- Steven & Alexandra Cohen Foundation
- Responsible party
- Principal investigator, Benjamin Kelmendi, MD, Yale University
- Investigators
- Benjamin Kelmendi, MD, Principal investigator, Yale UniversityTerence Ching, PhD, Principal investigator, Yale University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05370911
- Sponsor's protocol ID
- 2000032623
- Status last verified
- Jun 2026
- First submitted
- 19 Apr 2022
- Last updated
- 4 Jun 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No
Publications
Moreno FA, Wiegand CB, Taitano EK, Delgado PL. Safety, tolerability, and efficacy of psilocybin in 9 patients with obsessive-compulsive disorder. J Clin Psychiatry. 2006 Nov;67(11):1735-40. doi: 10.4088/jcp.v67n1110.
PubMed 17196053Davis AK, Barrett FS, May DG, Cosimano MP, Sepeda ND, Johnson MW, Finan PH, Griffiths RR. Effects of Psilocybin-Assisted Therapy on Major Depressive Disorder: A Randomized Clinical Trial. JAMA Psychiatry. 2021 May 1;78(5):481-489. doi: 10.1001/jamapsychiatry.2020.3285.
PubMed 33146667Ross S, Bossis A, Guss J, Agin-Liebes G, Malone T, Cohen B, Mennenga SE, Belser A, Kalliontzi K, Babb J, Su Z, Corby P, Schmidt BL. Rapid and sustained symptom reduction following psilocybin treatment for anxiety and depression in patients with life-threatening cancer: a randomized controlled trial. J Psychopharmacol. 2016 Dec;30(12):1165-1180. doi: 10.1177/0269881116675512.
PubMed 27909164Griffiths RR, Johnson MW, Carducci MA, Umbricht A, Richards WA, Richards BD, Cosimano MP, Klinedinst MA. Psilocybin produces substantial and sustained decreases in depression and anxiety in patients with life-threatening cancer: A randomized double-blind trial. J Psychopharmacol. 2016 Dec;30(12):1181-1197. doi: 10.1177/0269881116675513.
PubMed 27909165Ching THW, Amoroso L, Bohner C, D'Amico E, Eilbott J, Entezar T, Fitzpatrick M, Fram G, Grazioplene R, Hokanson J, Kichuk SA, Martins B, Patel P, Schaer H, Shnayder S, Witherow C, Pittenger C, Kelmendi B. 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. Front Psychiatry. 2024 Jan 9;14:1278823. doi: 10.3389/fpsyt.2023.1278823. eCollection 2023.
PubMed 38264632
Study at a glance
From the registry record, last updated by the sponsor on 4 Jun 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Effects of Repeated Dosing of Psilocybin on Obsessive-Compulsive Disorder: A Randomized, Waitlist-Controlled Study
- ClinicalTrials.gov ID
- NCT05370911
- Acronym / sponsor ID
- 2000032623
- Conditions
- Obsessive-Compulsive Disorder
- Keywords
- Psilocybin
- Phase
- Phase 1
- Study type
- Interventional
- Recruitment status
- Active, not recruiting
- Enrolment
- 28 participants (actual)
- Lead sponsor
- Yale UniversityUniversity, hospital or other
- Collaborators
- Steven & Alexandra Cohen Foundation
- Study start
- 20 Jul 2023 (actual)
- Primary completion
- 17 Feb 2026 (actual)
- Study completion
- Feb 2027 (estimated)
- First posted
- 12 May 2022 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Detailed description
Aim 1: To examine the effects of two doses of psilocybin on OCD symptoms among participants in the immediate treatment condition, compared to participants in the waitlist control/delayed treatment condition. The investigators hypothesize that participants in the immediate treatment group will report statistically significantly greater symptom improvement from baseline 4 days post-second dose, compared to participants in the waitlist control/delayed treatment group at the same interval during their waitlist phase.
Aim 2: To examine the effects of two doses of psilocybin on OCD symptoms, compared to one dose. The investigators hypothesize that two doses of oral psilocybin will reduce OCD symptoms to a statistically significantly greater extent than one dose.
This study aims to investigate the effects of repeated dosing of oral psilocybin on OCD symptomatology and assess psychological mechanisms that may mediate psilocybin's therapeutic effects on OCD. This study will employ a randomized, waitlist-controlled design with blinded independent ratings, with participants randomized to receive either immediate treatment (two doses oral psilocybin separated by one week) or delayed treatment (7 weeks post-randomization). An adaptive dose selection strategy will be implemented, with the first dose being standardized at 25 mg of psilocybin, and the second dose being either the same or a higher dosage (i.e., 30 mg) on the basis of a clinically significant response from baseline or not, respectively, 4 days post-first dose.
This study is conducted entirely on an outpatient basis with the possibility of remote/virtual follow-up visits after each dosing session. The dosing sessions last the entire day, and participants will be medically cleared prior to being permitted to return home with assistance (e.g., driven by a family member or friend, or ride share).
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Single blind (outcomes assessor)
- Number of arms
- 2
- Model description
- In the study, participants will be randomized to receive either immediate treatment with two doses of oral psilocybin separated by one week (n = 15) or enter a waitlist control/delayed treatment group and receive the same treatment 7 weeks post-randomization (n = 15).
| Arm | Type | Receives |
|---|---|---|
| Immediate Treatment | Experimental | Drug: PsilocybinParticipants randomized to this condition will receive treatment immediately, facilitated by two study staff members, and which consists of two preparatory sessions, followed by the first dosing session and two integration sessions, then the second dosing session and two integration sessions. This is followed by follow-up and long-term follow-up visits up to 12 months post-second dose. |
| Waitlist Control/Delayed Treatment | No intervention | –Participants randomized to this condition will first enter a waitlist phase that lasts for 7 weeks, after which rater unblinding will occur, and participants will be rescreened. If participants remain eligible at this time, they will begin their treatment phase. During their treatment phase, participants in this condition will receive the same treatment as described for participants in the immediate treatment group. This is followed by follow-up and long-term follow-up visits up to 12 months post-second dose. |
Who may qualify
- Ages
- 18 to 65 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (12 listed)
- Primary DSM-5 diagnosis of OCD, with Y-BOCS-II score of 26 or greater at screening
- Failed at least one medication and/or therapy trial of standard care treatment for OCD
- English fluency
- Agree to sign a medical release for investigators to communicate directly with participants' providers to confirm medication and psychotherapy histories or arrange contingencies in event of crises.
- Agree to provide an adult contact (relative, spouse, close friend or other caregiver) who is willing and able to be reached by the PI and/or study personnel in the event of an emergency, and who can provide transportation for study visits and independently comment on any changes in the participant's mood or behavior after each administration of psilocybin.
Key exclusion criteria (15 listed)
- Personal or immediate (first-degree relative) family history of formally diagnosed schizophrenia or other psychotic disorders, or bipolar I/II disorder
- Lack of knowledge about biological families' medical history, due to adoption or other circumstance
- Active suicidal intent or suicidal or non-suicidal self-injurious behaviors
- Unremitted Tourette syndrome
- Lifetime diagnosis of autism spectrum disorder
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| PsilocybinThe first oral dose will be 25 mg, and the second dose will be either 25 mg or 30 mg, depending on response to first dose. Psilocybin is a naturally occurring hallucinogenic ingredient found in some varieties of mushrooms that can be produced synthetically. It is considered to be a serotonergic psychedelic. We will use synthetically produced oral psilocybin in this study. Other Names: "Magic Mushrooms" | Drug | Immediate Treatment |
Primary outcome
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.
29 secondary outcomes
Change in Montgomery-Asberg Depression Scale (MADRS) total score from baseline at 4 days post-second dose
Time frame: Baseline & 4 days post-second dose
Change in Dimensional Obsessive-Compulsive Scale (DOCS) total score from baseline at 4 days post-second dose
Time frame: Baseline & 4 days post-second dose
Change in Obsessive Beliefs Questionnaire-44 (OBQ-44) total score from baseline at 4 days post-second dose
Time frame: Baseline & 4 days post-second dose
Change in Acceptance and Action Questionnaire for Obsessions and Compulsions (AAQ-OC) total score from baseline at 4 days post-second dose
Time frame: Baseline & 4 days post-second dose
Change in Tolerance of Uncontrollability Questionnaire (TOUQ) total score from baseline at 4 days post-second dose
Time frame: Baseline & 4 days post-second dose
Change in White Bear Suppression Inventory (WBSI) total score from baseline at 4 days post-second dose
Time frame: Baseline & 4 days post-second dose
Change in Difficulties in Emotion Regulation Scale (DERS) total score from baseline at 4 days post-second dose
Time frame: Baseline & 4 days post-second dose
Change in Southampton Mindfulness Questionnaire (SMQ) total score from baseline at 4 days post-second dose
Time frame: Baseline & 4 days post-second dose
Toronto Mindfulness Scale (TMS)
Time frame: Up to 3 weeks for immediate treatment condition, and up to 10 weeks for waitlist condition
Set, Setting, and Intentions (SSI) Scale
Time frame: Up to 3 weeks for immediate treatment condition, and up to 10 weeks for waitlist condition
Mystical Experience Questionnaire (MEQ)
Time frame: Up to 3 weeks for immediate treatment condition, and up to 10 weeks for waitlist condition
Psychological Insight Questionnaire (PIQ)
Time frame: Up to 3 weeks for immediate treatment condition, and up to 10 weeks for waitlist condition
Challenging Experience Questionnaire (CEQ)
Time frame: Up to 3 weeks for immediate treatment condition, and up to 10 weeks for waitlist condition
Ego Dissolution Inventory (EDI)
Time frame: Up to 3 weeks for immediate treatment condition, and up to 10 weeks for waitlist condition
Emotional Breakthrough Inventory (EBI)
Time frame: Up to 3 weeks for immediate treatment condition, and up to 10 weeks for waitlist condition
Change in Self-Compassion Scale (SCS) total mean score from baseline at 4 days post-second dose
Time frame: Baseline & 4 days post-second dose
Change in Ten-Item Personality Inventory (TIPI) total score from baseline at 4 days post-second dose
Time frame: Screening, 4 days and 12 months post-second dose
Change in Persisting Effects Questionnaire (PEQ) subscale scores from 4 weeks post-second dose at 12 months post-second dose
Time frame: 4 weeks post-second dose & 12 months post-second dose
Change in Alcohol Use Disorders Identification Test (AUDIT) total score from baseline at 4 weeks post-second dose
Time frame: Baseline & 4 weeks post-second dose
Change in Drug Use Disorders Identification Test (DUDIT) total score from baseline at 4 weeks post-second dose
Time frame: Baseline & 4 weeks post-second dose
Change in Fagerstrom Test for Nicotine Dependence (FTND) total score from baseline at 4 weeks post-second dose
Time frame: Baseline & 4 weeks post-second dose
Change in World Health Organization Disability Assessment Scale, v2.0 (WHODAS-2.0) 12-item, self-administered version total score from baseline at 4 days post-second dose
Time frame: Baseline & 4 weeks post-second dose
Change in Quality of Life Enjoyment & Satisfaction Questionnaire - Short Form (Q-LES-Q-SF) percentage maximum score from baseline at 4 days post-second dose
Time frame: Baseline & 4 weeks post-second dose
Writing task
Time frame: Baseline & 4 days post-second dose
Columbia Suicide Severity and Risk Scale (C-SSRS) Since Last Visit version
Time frame: Every study visit through study completion, an average of 12 months and 3 weeks for immediate treatment condition, and an average of 12 months and 10 weeks for waitlist condition
Theoretical Orientation Profile Scale-Revised (TOPS-R)
Time frame: Baseline
Working Alliance Inventory-Short Revised (WAI-SR)
Time frame: Up to 4 days post-second dose
Change in Symptom Provocation Task (SPT) ratings from baseline at 4 days post-second dose
Time frame: Baseline & 4 days post-second dose
Stanford Expectations of Treatment Scale (SETS)
Time frame: Baseline
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 4 Jun 2026.
- Background: PubMed 17196053Moreno FA, Wiegand CB, Taitano EK, Delgado PL. Safety, tolerability, and efficacy of psilocybin in 9 patients with obsessive-compulsive disorder. J Clin Psychiatry. 2006 Nov;67(11):1735-40. doi: 10.4088/jcp.v67n1110.
- Background: PubMed 33146667Davis AK, Barrett FS, May DG, Cosimano MP, Sepeda ND, Johnson MW, Finan PH, Griffiths RR. Effects of Psilocybin-Assisted Therapy on Major Depressive Disorder: A Randomized Clinical Trial. JAMA Psychiatry. 2021 May 1;78(5):481-489. doi: 10.1001/jamapsychiatry.2020.3285.
- Background: PubMed 27909164Ross S, Bossis A, Guss J, Agin-Liebes G, Malone T, Cohen B, Mennenga SE, Belser A, Kalliontzi K, Babb J, Su Z, Corby P, Schmidt BL. Rapid and sustained symptom reduction following psilocybin treatment for anxiety and depression in patients with life-threatening cancer: a randomized controlled trial. J Psychopharmacol. 2016 Dec;30(12):1165-1180. doi: 10.1177/0269881116675512.
- Background: PubMed 27909165Griffiths RR, Johnson MW, Carducci MA, Umbricht A, Richards WA, Richards BD, Cosimano MP, Klinedinst MA. Psilocybin produces substantial and sustained decreases in depression and anxiety in patients with life-threatening cancer: A randomized double-blind trial. J Psychopharmacol. 2016 Dec;30(12):1181-1197. doi: 10.1177/0269881116675513.
- Derived from this study: PubMed 38264632Ching THW, Amoroso L, Bohner C, D'Amico E, Eilbott J, Entezar T, Fitzpatrick M, Fram G, Grazioplene R, Hokanson J, Kichuk SA, Martins B, Patel P, Schaer H, Shnayder S, Witherow C, Pittenger C, Kelmendi B. 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. Front Psychiatry. 2024 Jan 9;14:1278823. doi: 10.3389/fpsyt.2023.1278823. eCollection 2023.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Benjamin Kelmendi, MD principal investigator
Yale University
Terence Ching, PhD principal investigator
Yale University
2 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 1 study testing Psilocybin in people with Obsessive-Compulsive Disorder, run by Yale University at 2 sites in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 12 inclusion and 15 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: under way, not looking for participants, as of the sponsor's last update on 4 Jun 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 2 sites in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
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). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT05370911, which also lists 5 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 4 Jun 2026.