Subjective Experience Following Psilocybin

The overall goal of this clinical trial is to systematically explore the relationship between the subjective psychedelic experience, improvements in well-being, and the stress response following psilocybin administration.

The investigators aim to determine whether blocking the acute subjective effects (via risperidone) will influence the acute or protracted effects of psilocybin as measured via self-report, biochemical, or psychophysiological measures. The study also aims to determine if individual variability in stress reactivity or regulation predicts acute (day of dosing) or protracted (1-week later) effects of psilocybin.

A single site will recruit 128 participants aged 18 to 65 who do not meet criteria for any psychiatric diagnoses. A series of questionnaires, blood labs, and medical exams including electrocardiogram will determine inclusion into the study. Once accepted into the study, participants will complete baseline measures assessing biomarkers such as cortisol and brain-derived neurotrophic factor (BDNF) levels, cognitive flexibility, mood, well-being, personality traits, and anxiety levels.

Participants will then be randomly assigned into one of the following groups:

i) high dose psilocybin in combination with placebo pretreatment ii) high dose psilocybin in combination with risperidone pretreatment iii) low dose psilocybin in combination with placebo pretreatment iv) low dose psilocybin in combination with risperidone pretreatment

Outcome measures will be assessed at 1-week and 1-month after each dosing session.

Inclusion criteria

• Individuals of all sexes, gender identities, and ethnicities
• Ages 18 to 65 years of age at the time of screening
• Ability to read/write in English
• Agree not to consume psychoactive drugs 24 hours before dosing sessions or consume psychedelics during duration of study participation

Exclusion criteria

• Any notable abnormality on electrocardiogram or routine medical blood or urinalysis laboratory tests
• Current psychiatric diagnoses, such as: major depressive disorder, generalized anxiety disorder, panic disorder, social anxiety disorder, obsessive compulsive disorder, moderate to severe substance use disorders, eating disorders, personality disorders, post-traumatic stress disorder
• Lifetime or current psychiatric diagnoses of: psychosis, schizophrenia, bipolar disorder
• Family history: a first- or second degree relative with a history of schizophrenia or other psychotic disorders, bipolar I or II
• Medication: Any medication with the potential to interact with the investigational medicinal products, especially those with serotonergic mechanisms of actions like SSRIs, SNRIs or MAO-Inhibitors as well as other antipsychotics
• Currently pregnancy or nursing, trying to become pregnant, or unwilling to use acceptable method of contraception during the study
• Current or recent (within 12 weeks) participation in a clinical trial involving medication administration
• Cognitive impairment (Folsetin Mini Mental State Exam score < 24)
• A disorder that may interfere with drug absorption, distribution, metabolism, or excretion (including gastrointestinal surgery).
• Suffered a traumatic brain injury with one of the following symptoms Loss of consciousness >30min Alteration of consciousness/mental state >24h Post-traumatic amnesia >1 day Glasgow Coma Scale (best available score in first 24 hours) <13
• Any other circumstances that, in the opinion of the investigators, compromises participant safety