Obsessive-Compulsive DisorderPhase 1PAP-OCDNCT06299319
Feasibility, Clinical Effects, and Safety of Psilocybin-assisted Psychotherapy for Treatment-resistant OCD
A Phase 1 study testing Psilocybin in people with Obsessive-Compulsive Disorder, run by Centre for Addiction and Mental Health at 1 site in Canada.
Trial summary
Psilocybin, the chemical component of "magic mushrooms", has been administered with psychotherapy in several randomized clinical trials (RCTs) showing large and sustained antidepressant effects. There is interest to see if similar effects may be provided in those with obsessive compulsive disorder (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
- 10 participants
- Where
- 1 siteCanada
- Study dates
- 1 Sep 2024to 4 Sep 2026
- Phase
- Phase 1
- Are there results?
- None posted in the registry
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
- Adults 18 to 65 years old;
- Are outpatients
- Must be deemed to have capacity to provide informed consent;
- Must sign and date the informed consent form;
- Stated willingness to comply with all study procedures;
- Ability to read and communicate in English, such that their literacy and comprehension is sufficient for understanding the consent form and study questionnaires, as evaluated by study staff obtaining consent;
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- Primary The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) diagnosis of obsessive compulsive disorder (OCD) based on medical records and assessment using the Structured Clinical Interview for DSM-5 (SCID-5) administered at the first screening visit;
- Participants diagnosed with treatment-resistant OCD defined as individuals with a score of ≥ 16 on the YBOCS (i.e. moderate symptom severity) and that have not responded to two or more separate pharmacological interventions and one or more trials of cognitive behavioural therapy (CBT); there is no upper limit on the number of treatment failures;
- Individuals with an estimated glomerular filtration rate (eGFR) above 40mL/min/1.73m2 and all blood work within normal limits as assessed by clinical laboratory tests at Screening (V1)
- Ability to take oral medication;
- Individuals who are capable of becoming pregnant: use of highly effective contraception for at least 1 month prior to screening and agreement to use such a method during study participation;
- Individuals who are willing to and have tapered off current OCD medications for a minimum of 2-weeks prior to Baseline (V2) and whose physician confirms that it is safe for them to do so;
- Individuals who are willing to and have tapered off current inhibitors of 5'-diphospho-glucuronosyltransferase (UGT)1A9 and 1A10, aldehyde dehydrogenase inhibitors (ALDHs) and alcohol dehydrogenase inhibitors (ADHs) for a minimum of 2-weeks (or more depending on the medication) prior to Baseline (V2) and for the duration of the study and whose physician confirms that it is safe for them to do so; and
- Agreement to adhere to Lifestyle Considerations (section 4.5) throughout study duration.
Who cannot join
- Pregnant as assessed by a urine pregnancy test at Screening (V1) and Baseline (V2) or individuals that intend to become pregnant during the study or are breastfeeding;
- Treatment with another investigational drug or other intervention within 30 days of Screening (V1);
- Have initiated psychotherapy in the preceding 12 weeks prior to Screening (V1);
- Have a DSM-5 diagnosis of substance use disorder (use of tobacco and prescribed opioids are permitted) within the preceding 6 months;
- Have active suicidal ideation as determined by the C-SSRS and/or clinical interview. Significant suicide risk is defined by suicidal ideation as endorsed by items 4 or 5 of the C-SSRS;
- Any DSM-5 lifetime diagnosis of a schizophrenia-spectrum disorder; psychotic disorder (unless substance induced or due to a medical condition), bipolar I or II disorder, paranoid personality disorder, borderline personality disorder, or neurocognitive disorder as determined by medical history and the SCID-5 clinical interview;
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- Any first-degree relative with a diagnosis of schizophrenia-spectrum disorder; psychotic disorder (unless substance-induced or due to a medical condition); or bipolar I or II disorder as determined by the family medical history form and discussions with the participant;
- Have contraindications to transcranial magnetic stimulation (TMS) as determined by the transcranial magnetic stimulation adult safety screen (TASS) questionnaire;
- Have a history of seizures;
- Are taking anticonvulsants or benzodiazepines (Lorazepam up to 2mg/day is acceptable);
- Presence of a relative or absolute contraindication to psilocybin, including a drug allergy, recent stroke history, uncontrolled hypertension, low or labile blood pressure, recent myocardial infarction, cardiac arrhythmic, severe coronary artery disease, or moderate to severe renal or hepatic impairment;
- Use of classic psychedelic drugs within the previous 12 months; OR
- Any other clinically significant physical illness including chronic infectious diseases or any other major concurrent illness that, in the opinion of the investigator, may interfere with the interpretation of the study results or constitute a health risk for the participant if they take part in the study.
Trial locations and contacts
1 site in 1 country.
About this study
Official title: Evaluating the Feasibility, Clinical Effects, and Safety of Psilocybin-assisted Psychotherapy for Treatment-resistant Obsessive-compulsive Disorder: An Open-label Clinical Trial
Psilocybin, the chemical component of "magic mushrooms", has been administered with psychotherapy in several randomized clinical trials (RCTs) showing large and sustained antidepressant effects. There is interest to see if similar effects may be provided in those with obsessive compulsive disorder (OCD).
The purpose of this study is to evaluate the safety, feasibility, and clinical effects of psilocybin administration in those with OCD. Ten participants with treatment-resistant OCD will receive two doses of 25mg of psilocybin under supportive conditions, two weeks apart. The investigators hypothesize that two sessions of psilocybin 25mg administered under supportive conditions to participants with treatment-resistant OCD will lead to significant reductions in OCD symptoms.
Read the detailed description
Literature suggests that up to 40 percent of individuals with OCD do not respond to conventional treatment and experience treatment resistant OCD (TROCD) (1, 2). Psilocybin, the chemical component of "magic mushrooms", has been administered with psychotherapy in several randomized clinical trials (RCTs) showing large and sustained antidepressant effects (3). Results of these trials have led to growing calls for transition to clinical use, as well as increased research for other mental health disorders. It is presumed that psilocybin's therapeutic effects are induced by the psychedelic "trip", which is dependent on serotonin 2A receptor (5-HT2AR) activation (4, 5). All studies have used psilocybin in conjunction with psychotherapy involving two therapists present during full-day dosing sessions. There is a need for more data in the TROCD population as there is only one clinical trial published for this specific population, followed by various case reports.
Using a proof-of-concept, open-label, clinical trial approach, 10 participants with TROCD will receive 2 doses of 25mg of psilocybin, with two weeks between each dosing day. The objectives of this study are as follows:
- To assess the safety, and feasibility, of psilocybin, administered with psychological support to adult participants with TROCD. Hypothesis 1: The investigators will be able to recruit and retain ten participants with TROCD for the duration of the trial and that psychedelic-assisted psychotherapy for obsessive compulsive disorder (PAP-OCD) will be safe in those with TROCD, as measured by monitoring adverse events and using the Columbia Suicide Severity Rating Scale (C-SSRS).
- To assess the clinical effects of PAP in those with TROCD. Hypothesis 2: Two sessions of psilocybin (25mg) administered under supportive conditions to participants with TROCD will lead to significant reductions in OCD symptoms as measured by the Yale-Brown Obsessive Compulsive Scale (YBOCS) when comparing baseline to Week 3.
- Provide pilot data on the effect of psilocybin and supportive therapy on TROCD in preparation of a future larger RCT.
Overview of Study Design:
All 10 participants will follow the same study design. Each participant will undergo a screening assessment where they will complete lab tests, and clinical and psychiatric assessments to determine eligibility. Following the screening visit, participants will undergo a washout period where they will be tapered off concomitant medications over a medication the participant is being tapered off (based on the half-life of the medication) and the participant's preference for the length of the tapering period. All medications will require a minimum of a 2-week tapering period with the exception of fluoxetine which will require a minimum of 4-weeks. Additional time may be added at the discretion of the study investigator. During this period, there will be weekly check-ins with the study physician.
At study Visit 2 (Baseline, V2), participants will complete a series of questionnaires and assessments, preparatory therapy with trained study therapists, and undergo a brain functional magnetic resonance imaging (fMRI). The preparatory therapy sessions will build a therapeutic alliance, and provide psychoeducation about, and set intentions for, the psilocybin session. To reduce participant burden, baseline can be broken up into multiple days, however all assessments must be completed within 7-days of the first dose. At study Visit 3 (V3), neurophysiological measurements will be performed.
Upon completion of V2 and V3, participants will undergo the first psilocybin dosing session at Visit 4 (V4) where they will receive an active dose (25mg) of psilocybin in conjunction with supportive therapy. The psilocybin session will last 5 to 6 hours and will be conducted in the existing psychedelic treatment suite developed at the Centre for Addiction and Mental Health (CAMH). Two trained study therapists will be supporting each participant during the dosing session. After 5 hours of dose administration, participants will be evaluated for safety by the study psychiatrist and discharged home in the company of a caregiver or a family member.
On the day after the dosing session (Visit 5, V5) and one-week after the dosing session (Visit 6, V6), participants will be asked to complete the same questionnaires that were done at Baseline (V2) and will undergo an integrative therapy session with the trained study therapist.
Between Visit 5 (V5) and Visit 7 (V7), during study Visit 6 (V6), the same neurophysiological measurements will be performed as during Visit 3 (V3). Follow-up assessments will also occur at 3, 6, 9 and 12 weeks (Visit 7, 8, 9 and 10) after the second psilocybin dosing session. The same questionnaires administered at Baseline (V2) will be repeated at each of these study visits.
- Conditions
- Obsessive-Compulsive Disorder
- Being tested
- Psilocybin
- Keywords
- psilocybin, psychedelics, obsessive-compulsive disorder, clinical trial
- 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
Also called PEX010
The psilocybin used in this study meets quality specifications suitable for human research use. The active drug is encapsulated using a hydroxypropyl methylcellulose (HPMC) capsule and contains 25 mg of psilocybin. The psilocybin will be administered twice during the trial, in conjunction with supportive therapy.
| Study group | Role | What they receive |
|---|---|---|
| Experimental: Psilocybin 25 mg | Experimental | Participants will receive a 25 mg dose of psilocybin, twice throughout the trial, with two weeks in between doses. Receives: Drug: Psilocybin |
What is being measured
The primary outcome is the main question the study is designed to answer.
Feasibility of administering psilocybin (25 mg) in adults with treatment-resistant OCD
Percentage of participants recruited and retained
Measured: Screening Period, Intervention (2 weeks), Follow-up after 2nd dosing session (up to 10 weeks after 2nd dose)
Incidence of adverse events (Safety and Tolerability)
Frequency of dropouts attributed to adverse effects or serious adverse events
Measured: Screening Period, Intervention (2 weeks), Follow-up after 2nd dosing session (up to 10 weeks after 2nd dose)
Change in the Yale-Brown Obsessive-Compulsive Scale (YBOCS) total score from baseline
The Yale-Brown Obsessive-Compulsive Scale is a test to rate the severity of obsessive-compulsive disorder symptoms. It is a 10-item scale, with questions 1-5 regarding obsessions, and questions 6-10 regarding compulsions. Each item is scored from 1-4, for a total possible score of 40.
Higher scores represent a more severe condition.
Measured: Baseline (Day -1) to Week 3 (Day 21)
Secondary outcomes (7)
Proportion of participants who respond to treatment
Response to treatment defined as a 35 percent or more reduction of the Yale-Brown Obsessive-Compulsive Scale (YBOCS) total score, and remission defined as a score of less than or equal to 7 on the YBOCS.
The Yale-Brown Obsessive-Compulsive Scale is a test to rate the severity of obsessive-compulsive disorder symptoms. It is a 10-item scale, with questions 1-5 regarding obsessions, and questions 6-10 regarding compulsions. Each item is scored from 1-4, for a total possible score of 40.
Higher scores represent a more severe condition.
Measured: Baseline (Day -1) to Week 3 (Day 21)
Changes in Patient Health Questionnaire (PHQ-9) from Baseline to Week 3
The PHQ-9 is a multipurpose instrument for screening, diagnosing, monitoring and measuring the severity of depression.
It is a 9-item scale, with each item score ranging from 0 ("Not at all") to 3 ("Nearly every day") for a total possible score of 27.
Higher scores represent a more severe condition.
Measured: Baseline (Day -1) to Week 3 (Day 21)
Change in the Clinical Global Impression (CGI) scale from Baseline to Week 3
The Clinical Global Impression (CGI) scale is a 3-item observer-rated scale that measures illness severity, global improvement or change, and therapeutic response. The "Severity" and "Global Improvement or Change" items are scored on a 7-point scale, ranging from 0-7. The "Therapeutic Response" item is scored from 1-16.
Higher scores represent a worse outcome.
Measured: Baseline (Day -1) to Week 3 (Day 21)
Change in the World Health Organization Quality of Life Short Version (WHOQOL-BREF) score from Baseline to Week 3
The World Health Organization Quality of Life Short Version (WHOQOL-BREF) is a 26-item instrument consisting of four domains: physical health (7 items), psychological health (6 items), social relationships (3 items), and environmental health (8 items); it also contains quality of life and general health items. Each individual item of the WHOQOL-BREF is scored from 1 to 5.
Higher scores represent worse quality of life.
Measured: Baseline (Day -1) to Week 3 (Day 21)
Change in World Health Organization Disability Assessment Schedule (WHODAS 2.0) from Baseline to Week 3
WHODAS 2.0 is an instrument that assesses functioning. The instrument produces domain-specific scores for six different functioning domains - cognition, mobility, self-care, getting along, life activities (household and work) and participation.
Measured: Baseline (Day -1) to Week 3 (Day 21)
Change in Generalized Anxiety Disorder (GAD-7) scores from Baseline to Week 3
The GAD-7 measures severity of anxiety symptoms. It is a 7-item scale, with each item ranging from 0 ("Not at all") to 3 ("Nearly every day"), for a total possible score of 21.
Higher scores represent a more severe condition.
Measured: Baseline (Day -1) to Week 3 (Day 21)
Changes in behavioural assessments for well-being (Warwick-Edinburgh Mental Wellbeing Scale; WEMWBS) from Baseline to Week 3
WEMWBS is a scale which has been validated for the measurement of mental wellbeing. It is a 14-item scale consisting of positively worded statements, ranging from 1 ("None of the time") to 5 ("All of the time").
Higher scores represent greater wellbeing.
Measured: Baseline (Day -1) to Week 3 (Day 21)
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted7 Mar 2024
- Study start1 Sep 2024
- Primary completion4 Sep 2026
- Study completion4 Sep 2026
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 Centre for Addiction and Mental HealthThe 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
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Enrolment
- 10 participants (actual)
Sponsor and investigators
- Lead sponsor
- Centre for Addiction and Mental Health
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
- Investigators
- Gwyneth Zai, MD, MSc, PhD, Principal investigator, Centre for Addiction and Mental Health
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06299319
- Sponsor's protocol ID
- 149-2021
- Acronym
- PAP-OCD
- Status last verified
- Mar 2026
- First submitted
- 15 Feb 2024
- Last updated
- 24 Sep 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Publications
Bloch MH, Landeros-Weisenberger A, Kelmendi B, Coric V, Bracken MB, Leckman JF. A systematic review: antipsychotic augmentation with treatment refractory obsessive-compulsive disorder. Mol Psychiatry. 2006 Jul;11(7):622-32. doi: 10.1038/sj.mp.4001823. Epub 2006 Apr 4.
PubMed 16585942Pallanti S, Quercioli L. Treatment-refractory obsessive-compulsive disorder: methodological issues, operational definitions and therapeutic lines. Prog Neuropsychopharmacol Biol Psychiatry. 2006 May;30(3):400-12. doi: 10.1016/j.pnpbp.2005.11.028. Epub 2006 Feb 28.
PubMed 16503369Perkins D, Sarris J, Rossell S, Bonomo Y, Forbes D, Davey C, Hoyer D, Loo C, Murray G, Hood S, Schubert V, Galvao-Coelho NL, O'Donnell M, Carter O, Liknaitzky P, Williams M, Siskind D, Penington D, Berk M, Castle D. Medicinal psychedelics for mental health and addiction: Advancing research of an emerging paradigm. Aust N Z J Psychiatry. 2021 Dec;55(12):1127-1133. doi: 10.1177/0004867421998785. Epub 2021 Mar 21.
PubMed 33745287Halberstadt AL, Koedood L, Powell SB, Geyer MA. Differential contributions of serotonin receptors to the behavioral effects of indoleamine hallucinogens in mice. J Psychopharmacol. 2011 Nov;25(11):1548-61. doi: 10.1177/0269881110388326. Epub 2010 Dec 8.
PubMed 21148021Madsen MK, Fisher PM, Burmester D, Dyssegaard A, Stenbaek DS, Kristiansen S, Johansen SS, Lehel S, Linnet K, Svarer C, Erritzoe D, Ozenne B, Knudsen GM. Psychedelic effects of psilocybin correlate with serotonin 2A receptor occupancy and plasma psilocin levels. Neuropsychopharmacology. 2019 Jun;44(7):1328-1334. doi: 10.1038/s41386-019-0324-9. Epub 2019 Jan 26.
PubMed 30685771
Study at a glance
From the registry record, last updated by the sponsor on 24 Sep 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Evaluating the Feasibility, Clinical Effects, and Safety of Psilocybin-assisted Psychotherapy for Treatment-resistant Obsessive-compulsive Disorder: An Open-label Clinical Trial
- ClinicalTrials.gov ID
- NCT06299319
- Acronym / sponsor ID
- PAP-OCD / 149-2021
- Conditions
- Obsessive-Compulsive Disorder
- Keywords
- psilocybin, psychedelics, obsessive-compulsive disorder, clinical trial
- Phase
- Phase 1
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 10 participants (actual)
- Lead sponsor
- Centre for Addiction and Mental HealthUniversity, hospital or other
- Study start
- 1 Sep 2024 (actual)
- Primary completion
- 4 Sep 2026 (actual)
- Study completion
- 4 Sep 2026 (actual)
- First posted
- 7 Mar 2024 (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.
Psilocybin, the chemical component of "magic mushrooms", has been administered with psychotherapy in several randomized clinical trials (RCTs) showing large and sustained antidepressant effects. There is interest to see if similar effects may be provided in those with obsessive compulsive disorder (OCD).
The purpose of this study is to evaluate the safety, feasibility, and clinical effects of psilocybin administration in those with OCD. Ten participants with treatment-resistant OCD will receive two doses of 25mg of psilocybin under supportive conditions, two weeks apart. The investigators hypothesize that two sessions of psilocybin 25mg administered under supportive conditions to participants with treatment-resistant OCD will lead to significant reductions in OCD symptoms.
Detailed description
Literature suggests that up to 40 percent of individuals with OCD do not respond to conventional treatment and experience treatment resistant OCD (TROCD) (1, 2). Psilocybin, the chemical component of "magic mushrooms", has been administered with psychotherapy in several randomized clinical trials (RCTs) showing large and sustained antidepressant effects (3). Results of these trials have led to growing calls for transition to clinical use, as well as increased research for other mental health disorders. It is presumed that psilocybin's therapeutic effects are induced by the psychedelic "trip", which is dependent on serotonin 2A receptor (5-HT2AR) activation (4, 5). All studies have used psilocybin in conjunction with psychotherapy involving two therapists present during full-day dosing sessions. There is a need for more data in the TROCD population as there is only one clinical trial published for this specific population, followed by various case reports.
Using a proof-of-concept, open-label, clinical trial approach, 10 participants with TROCD will receive 2 doses of 25mg of psilocybin, with two weeks between each dosing day. The objectives of this study are as follows:
- To assess the safety, and feasibility, of psilocybin, administered with psychological support to adult participants with TROCD. Hypothesis 1: The investigators will be able to recruit and retain ten participants with TROCD for the duration of the trial and that psychedelic-assisted psychotherapy for obsessive compulsive disorder (PAP-OCD) will be safe in those with TROCD, as measured by monitoring adverse events and using the Columbia Suicide Severity Rating Scale (C-SSRS).
- To assess the clinical effects of PAP in those with TROCD. Hypothesis 2: Two sessions of psilocybin (25mg) administered under supportive conditions to participants with TROCD will lead to significant reductions in OCD symptoms as measured by the Yale-Brown Obsessive Compulsive Scale (YBOCS) when comparing baseline to Week 3.
- Provide pilot data on the effect of psilocybin and supportive therapy on TROCD in preparation of a future larger RCT.
Overview of Study Design:
All 10 participants will follow the same study design. Each participant will undergo a screening assessment where they will complete lab tests, and clinical and psychiatric assessments to determine eligibility. Following the screening visit, participants will undergo a washout period where they will be tapered off concomitant medications over a medication the participant is being tapered off (based on the half-life of the medication) and the participant's preference for the length of the tapering period. All medications will require a minimum of a 2-week tapering period with the exception of fluoxetine which will require a minimum of 4-weeks. Additional time may be added at the discretion of the study investigator. During this period, there will be weekly check-ins with the study physician.
At study Visit 2 (Baseline, V2), participants will complete a series of questionnaires and assessments, preparatory therapy with trained study therapists, and undergo a brain functional magnetic resonance imaging (fMRI). The preparatory therapy sessions will build a therapeutic alliance, and provide psychoeducation about, and set intentions for, the psilocybin session. To reduce participant burden, baseline can be broken up into multiple days, however all assessments must be completed within 7-days of the first dose. At study Visit 3 (V3), neurophysiological measurements will be performed.
Upon completion of V2 and V3, participants will undergo the first psilocybin dosing session at Visit 4 (V4) where they will receive an active dose (25mg) of psilocybin in conjunction with supportive therapy. The psilocybin session will last 5 to 6 hours and will be conducted in the existing psychedelic treatment suite developed at the Centre for Addiction and Mental Health (CAMH). Two trained study therapists will be supporting each participant during the dosing session. After 5 hours of dose administration, participants will be evaluated for safety by the study psychiatrist and discharged home in the company of a caregiver or a family member.
On the day after the dosing session (Visit 5, V5) and one-week after the dosing session (Visit 6, V6), participants will be asked to complete the same questionnaires that were done at Baseline (V2) and will undergo an integrative therapy session with the trained study therapist.
Between Visit 5 (V5) and Visit 7 (V7), during study Visit 6 (V6), the same neurophysiological measurements will be performed as during Visit 3 (V3). Follow-up assessments will also occur at 3, 6, 9 and 12 weeks (Visit 7, 8, 9 and 10) after the second psilocybin dosing session. The same questionnaires administered at Baseline (V2) will be repeated at each of these study visits.
Study design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| Experimental: Psilocybin 25 mg | Experimental | Drug: PsilocybinParticipants will receive a 25 mg dose of psilocybin, twice throughout the trial, with two weeks in between doses. |
Who may qualify
- Ages
- 18 to 65 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (14 listed)
- Adults 18 to 65 years old;
- Are outpatients
- Must be deemed to have capacity to provide informed consent;
- Must sign and date the informed consent form;
- Stated willingness to comply with all study procedures;
Key exclusion criteria (13 listed)
- Pregnant as assessed by a urine pregnancy test at Screening (V1) and Baseline (V2) or individuals that intend to become pregnant during the study or are breastfeeding;
- Treatment with another investigational drug or other intervention within 30 days of Screening (V1);
- Have initiated psychotherapy in the preceding 12 weeks prior to Screening (V1);
- Have a DSM-5 diagnosis of substance use disorder (use of tobacco and prescribed opioids are permitted) within the preceding 6 months;
- Have active suicidal ideation as determined by the C-SSRS and/or clinical interview. Significant suicide risk is defined by suicidal ideation as endorsed by items 4 or 5 of the C-SSRS;
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 |
|---|---|---|
| PsilocybinAlso: PEX010The psilocybin used in this study meets quality specifications suitable for human research use. The active drug is encapsulated using a hydroxypropyl methylcellulose (HPMC) capsule and contains 25 mg of psilocybin. The psilocybin will be administered twice during the trial, in conjunction with supportive therapy. | Drug | Experimental: Psilocybin 25 mg |
Primary outcome
Feasibility of administering psilocybin (25 mg) in adults with treatment-resistant OCD
Time frame: Screening Period, Intervention (2 weeks), Follow-up after 2nd dosing session (up to 10 weeks after 2nd dose)
Percentage of participants recruited and retained
Incidence of adverse events (Safety and Tolerability)
Time frame: Screening Period, Intervention (2 weeks), Follow-up after 2nd dosing session (up to 10 weeks after 2nd dose)
Frequency of dropouts attributed to adverse effects or serious adverse events
Change in the Yale-Brown Obsessive-Compulsive Scale (YBOCS) total score from baseline
Time frame: Baseline (Day -1) to Week 3 (Day 21)
The Yale-Brown Obsessive-Compulsive Scale is a test to rate the severity of obsessive-compulsive disorder symptoms. It is a 10-item scale, with questions 1-5 regarding obsessions, and questions 6-10 regarding compulsions. Each item is scored from 1-4, for a total possible score of 40. Higher scores represent a more severe condition.
7 secondary outcomes
Proportion of participants who respond to treatment
Time frame: Baseline (Day -1) to Week 3 (Day 21)
Changes in Patient Health Questionnaire (PHQ-9) from Baseline to Week 3
Time frame: Baseline (Day -1) to Week 3 (Day 21)
Change in the Clinical Global Impression (CGI) scale from Baseline to Week 3
Time frame: Baseline (Day -1) to Week 3 (Day 21)
Change in the World Health Organization Quality of Life Short Version (WHOQOL-BREF) score from Baseline to Week 3
Time frame: Baseline (Day -1) to Week 3 (Day 21)
Change in World Health Organization Disability Assessment Schedule (WHODAS 2.0) from Baseline to Week 3
Time frame: Baseline (Day -1) to Week 3 (Day 21)
Change in Generalized Anxiety Disorder (GAD-7) scores from Baseline to Week 3
Time frame: Baseline (Day -1) to Week 3 (Day 21)
Changes in behavioural assessments for well-being (Warwick-Edinburgh Mental Wellbeing Scale; WEMWBS) from Baseline to Week 3
Time frame: Baseline (Day -1) to Week 3 (Day 21)
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 24 Sep 2026.
- Background: PubMed 16585942Bloch MH, Landeros-Weisenberger A, Kelmendi B, Coric V, Bracken MB, Leckman JF. A systematic review: antipsychotic augmentation with treatment refractory obsessive-compulsive disorder. Mol Psychiatry. 2006 Jul;11(7):622-32. doi: 10.1038/sj.mp.4001823. Epub 2006 Apr 4.
- Background: PubMed 16503369Pallanti S, Quercioli L. Treatment-refractory obsessive-compulsive disorder: methodological issues, operational definitions and therapeutic lines. Prog Neuropsychopharmacol Biol Psychiatry. 2006 May;30(3):400-12. doi: 10.1016/j.pnpbp.2005.11.028. Epub 2006 Feb 28.
- Background: PubMed 33745287Perkins D, Sarris J, Rossell S, Bonomo Y, Forbes D, Davey C, Hoyer D, Loo C, Murray G, Hood S, Schubert V, Galvao-Coelho NL, O'Donnell M, Carter O, Liknaitzky P, Williams M, Siskind D, Penington D, Berk M, Castle D. Medicinal psychedelics for mental health and addiction: Advancing research of an emerging paradigm. Aust N Z J Psychiatry. 2021 Dec;55(12):1127-1133. doi: 10.1177/0004867421998785. Epub 2021 Mar 21.
- Background: PubMed 21148021Halberstadt AL, Koedood L, Powell SB, Geyer MA. Differential contributions of serotonin receptors to the behavioral effects of indoleamine hallucinogens in mice. J Psychopharmacol. 2011 Nov;25(11):1548-61. doi: 10.1177/0269881110388326. Epub 2010 Dec 8.
- Background: PubMed 30685771Madsen MK, Fisher PM, Burmester D, Dyssegaard A, Stenbaek DS, Kristiansen S, Johansen SS, Lehel S, Linnet K, Svarer C, Erritzoe D, Ozenne B, Knudsen GM. Psychedelic effects of psilocybin correlate with serotonin 2A receptor occupancy and plasma psilocin levels. Neuropsychopharmacology. 2019 Jun;44(7):1328-1334. doi: 10.1038/s41386-019-0324-9. Epub 2019 Jan 26.
- 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.
Gwyneth Zai, MD, MSc, PhD principal investigator
Centre for Addiction and Mental Health
1 site 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 Centre for Addiction and Mental Health at 1 site in Canada.
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 14 inclusion and 13 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: finished, as of the sponsor's last update on 24 Sep 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Canada. 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?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
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?
Feasibility of administering psilocybin (25 mg) in adults with treatment-resistant OCD (time frame: Screening Period, Intervention (2 weeks), Follow-up after 2nd dosing session (up to 10 weeks after 2nd dose)). The study lists 3 primary outcomes in all. 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 NCT06299319, 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 24 Sep 2026.