Pilot Study on the Effects of Psilocybin on Belief Updating and Insight Formation

NCT07818564 | Not Yet Recruiting Phase 1 FDA Drug

• 1 other identifier: STUDY00001310
• Study Type: interventional
• Target: 24
• Locations: 1 country
• Sites: 1

Brief Summary

The primary aim of this phase I mechanistic pilot study is to evaluate the effects of psilocybin on aspects of cognition in healthy adult volunteers. Up to 24 participants will receive a single dose of either psilocybin or inert placebo, and they will be asked to complete several computer-based behavioral tasks measuring features of learning, belief updating, and abstraction. Participants will also complete measures of subjective experience and expectancy, as well as semi-structured interviews at follow up, to assess whether experience correlates with behavior. This is a Voluntary Submission.

Conditions

Phase I

Keywords

psilocybin; psychedelic; cognition; learning; healthy volunteers

Outcome Measures

Primary Outcomes (2)

• Reinforcement Learning and Abstraction Task

  Custom computer-based behavioral task requiring participants to complete a series of puzzles to complete game levels. This task requires working memory and reinforcement learning, and it also includes a measure of state abstraction.

  During dosing session and 1 day after the dosing session

• Belief Updating Task

  Custom computer-based behavioral task in which participants must dynamically adjust predictions on each trial. This task measures trial to trial belief updating.

  1 day before dosing, during dosing, and 1 day after the dosing session

Secondary Outcomes (18)

• Altered States of Consciousness Questionnaire (ASC)

  During dosing session

• Mystical Experience Questionnaire (MEQ)

  During dosing session

• Psychological Insight Questionnaire (PIQ)

  During dosing session

• Emotional Breakthrough Inventory (EBI)

  During dosing session

• Challenging Experience Questionnaire (CEQ)

  During dosing session

Study Arms (2)

Psilocybin

EXPERIMENTAL

Psilocybin 25 mg oral capsule

Drug: Psilocybin (Usona Institute)

Inert Placebo

PLACEBO COMPARATOR

Microcrystalline cellulose 25 mg oral capsule

Drug: Inactive Placebo (Usona Institute)

Interventions

Psilocybin (Usona Institute) DRUG

1 dose of psilocybin 25 mg oral capsule

Psilocybin

Inactive Placebo (Usona Institute) DRUG

1 dose of Microcrystalline Cellulose (MCC) 25 mg capsule

Inert Placebo

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• be at least 18 years old at time of signing informed consent
• be fluent in speaking and reading English
• be able to swallow pills (capsules)
• agree to use highly effective birth control for at least one month prior to enrollment, and for the duration of study enrollment, whether male or female assigned at birth. Acceptable methods include: copper or hormonal coil intrauterine device (IUD), implanted or injected hormonal method, documented permanent sterilization, documented not able to become pregnant, or oral/intravaginal/transdermal hormones plus a barrier contraception. Two forms of contraception are required with any barrier method or with any oral, intravaginal, or transdermal hormonal method due to these methods not being considered highly effective alone. Abstinence alone is not an acceptable contraceptive method for this study.
• be healthy and psychologically stable as determined by screening for medical and psychiatric problems via a clinical interview, a medical questionnaire, a physical examination, an electrocardiogram (ECG), and routine laboratory tests
• agree to inform investigators within 48 hours of any new medical conditions, treatments, or procedures
• agree to refrain from using any psychoactive or recreational drugs, including cannabis, for the duration of study enrollment (with the exception of limited alcohol, nicotine, and caffeine as below)
• agree to refrain from drinking alcohol within 24 hours of all experimental sessions
• agree to consume approximately the same amount of caffeine and nicotine as on a usual day before experimental sessions, but to not consume any nicotine or caffeine closer than 1 hour prior to the scheduled dosing time. If the participant does not routinely consume caffeine or nicotine, they must agree not to do so for the duration of the study.
• agree to refrain from taking any "as needed" or "over the counter" medications (e.g., medications for pain, insomnia, or allergies) within 24 hours of all experimental sessions, unless previously approved by a study physician
• agree to store their phone and car keys in a locked storage locker for the duration of the experimental dosing session, and agree to stay on site for at least 6 hours after drug administration and until a physician agrees they are safe to leave the premises
• be able to identify two trusted support people (e.g. friend or family member, at least age 18 years of age), who are willing and able to serve as an emergency contact, and to pick the participant up and transport them home after the dosing session. One of these will be designated the primary support person, and the second will be backup to pick the person up in the event that the primary becomes unavailable.
• agree to not drive a motor vehicle or heavy machinery for 24 hours after the dosing session
• have used a classical psychedelic (5-HT2A agonist, such as psilocybin, LSD, DMT, 5-MeO-DMT, ayahuasca, mescaline) at least once in lifetime without clinically significant adverse effects

You may not qualify if:

• have used any psychedelic, hallucinogen, or entactogen, including 3,4-methylenedioxymethamphetamine (MDMA) and ketamine/esketamine, but not including cannabis, within the past 3 months
• unwilling or unable to stop using cannabis a minimum of one week prior to enrollment and to refrain from cannabis use for the duration of the study enrollment, to be tested with urine drug screens
• history of traumatic brain injury, or history of seizure disorder in adulthood
• history of any clinically significant cardiovascular condition, or condition that could make receiving the study drug harmful because of increases in blood pressure and heart rate. This includes, but is not limited to, uncontrolled hypertension, coronary artery disease, heart failure, stroke, myocardial infarction, artificial heart valve, aneurism, or clinically significant arrhythmia. Uncontrolled hypertension is defined here as repeated blood pressure readings of \>= 140 mmHg systolic or \>= 90 mmHg diastolic.
• baseline QTc \> 450 milliseconds (QTc is defined as the QT interval corrected for heart rate, either machine-read or manually over-read)
• current poorly controlled or insulin dependent diabetes mellitus (type I or type II)
• current clinically significant respiratory condition (supplemental oxygen requirement, or requiring hospitalization within the last year)
• current clinically significant liver or biliary disease, including recent laboratory abnormalities (AST or ALT \> 3x institutional upper limit of normal (ULN); total bilirubin \> 1.5 x ULN or direct bilirubin \< 35%), or based on the presence of ascites, encephalopathy, jaundice, esophageal varices, or coagulopathy
• clinically significant renal disease, including but not limited to CKD stage 3 or greater
• history of ever meeting Diagnostic and Statistical Manual, version 5 (DSM-5) criteria for any schizophrenia spectrum disorder, bipolar spectrum disorder, major depressive disorder with psychotic features, or any other psychotic disorder, including substance-induced psychotic disorders ever in lifetime
• have a first or second-degree relative with history of schizophrenia spectrum disorder, bipolar spectrum disorder, major depressive disorder with psychotic features, or other psychotic disorder including substance-induced psychotic disorders ever in lifetime
• clinically significant suicide risk, as determined by clinician judgment and the C-SSRS. Participants will be excluded if any current active suicidal ideation, including intent to kill oneself or preparatory behavior, or a lifetime history of suicide attempts including aborted or interrupted.
• history within last 5 years of inpatient psychiatric hospitalization for any reason
• lifetime history of hallucinogen persisting perception disorder
• current or history within the last 1 year of meeting DSM-5 criteria for an alcohol or substance use disorder, excluding caffeine and nicotine; or a lifetime history of hallucinogen use disorder

Sponsors & Collaborators

• Brown University: lead

Study Sites (1)

Brown University School of Public Health

Providence, Rhode Island, 02903, United States

Location

Related Publications (2)

• Lehnert L, Littman ML, Frank MJ. Reward-predictive representations generalize across tasks in reinforcement learning. PLoS Comput Biol. 2020 Oct 15;16(10):e1008317. doi: 10.1371/journal.pcbi.1008317. eCollection 2020 Oct.

  PMID: 33057329 BACKGROUND

• Nassar MR, Wilson RC, Heasly B, Gold JI. An approximately Bayesian delta-rule model explains the dynamics of belief updating in a changing environment. J Neurosci. 2010 Sep 15;30(37):12366-78. doi: 10.1523/JNEUROSCI.0822-10.2010.

  PMID: 20844132 BACKGROUND

MeSH Terms

Interventions

Psilocybin

Intervention Hierarchy (Ancestors)

Indole Alkaloids; Alkaloids; Heterocyclic Compounds; Indoles; Heterocyclic Compounds, 2-Ring; Heterocyclic Compounds, Fused-Ring; Tryptamines; Indolizidines; Indolizines

Study Design

• Study Type: interventional
• Phase: phase 1
• Allocation: RANDOMIZED
• Masking: TRIPLE
• Who Masked: PARTICIPANT, INVESTIGATOR, OUTCOMES ASSESSOR
• Purpose: BASIC SCIENCE
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: September 8, 2026
• First Posted: September 14, 2026
• Study Start (Estimated): November 1, 2026
• Primary Completion (Estimated): November 1, 2027
• Study Completion (Estimated): November 1, 2027
• Last Updated: September 14, 2026

Record last verified: 2026-08

Locations

US (1)