Case Studies in Psilocybin Research and Therapy

What Case Studies Can and Cannot Tell Us

Limitations of n=1 studies

A single case study cannot establish whether an intervention caused an outcome. Without a control condition, natural recovery, placebo effect, regression to the mean, and expectancy effects cannot be ruled out.

• Selection bias: People who report positive outcomes are more likely to submit case studies than those with neutral or negative experiences, creating systematic bias toward positive narratives.
• Recall bias: Retrospective accounts are filtered through memory. What people report may differ from what they experienced or scored on validated measures at the time.
• Generalisability: What was true for one person cannot be assumed true for others. Individual variation in pharmacology, psychology, and context is enormous.
• Attribution errors: Change may be attributed to psilocybin when it was actually driven by other concurrent factors — other therapy, life circumstances, or natural course of the condition.
• Dose uncertainty: In non-research contexts, dose and species are often estimated rather than precisely measured, limiting pharmacological interpretation.

What case studies do contribute

• Hypothesis generation: Case studies suggest patterns and mechanisms that controlled trials then test. Many important research questions first appeared as clinical observations.
• Rare event detection: Adverse effects occurring in fewer than 1 in 100 people may not appear in small trials. Case report networks are often the first to identify them.
• Mechanism illumination: The specific cognitive, emotional, and interpersonal changes through which improvement occurred — invisible in trial outcome data — are visible in case narratives.
• Population diversity: Controlled trials typically exclude many groups (psychiatric comorbidities, medication use, age extremes). Case studies capture real-world populations.
• Longitudinal depth: Case reports can follow a person for years, capturing how effects evolve in ways that standard trial follow-up windows cannot.

How case studies contribute to research

Case studies feed the research pipeline in several ways. When Moreno et al. observed marked OCD symptom reductions in nine psilocybin participants, this observation drove a hypothesis that could then be tested in controlled trials. When Johnson et al. noticed incidental reductions in smoking in early psilocybin study participants, this seeded a dedicated smoking cessation research programme. Details from case reports inform therapeutic protocol design — which aspects of preparation mattered most, how facilitators handled difficult experiences, what integration approaches helped — information that flows directly into the design of clinical trials.

Case Studies by Condition

Depressive Disorder

Depression — including major depressive disorder and treatment-resistant depression — has become the most extensively studied indication. The case literature encompasses rapid-onset effects appearing within days of a session (before neuroplastic changes could fully develop); long-duration remission lasting months or years after a single or paired session even in people who had been depressed for many years; and accounts highlighting recovery of anhedonia (the capacity for pleasure) as the most notable change. Case reports also document cases where concurrent SSRI use appeared to blunt both the experience and the therapeutic benefit — contributing to research interest in SSRI wash-out before psilocybin sessions. See Research Case Studies for the Davis et al. (2020) open-label MDD trial and related series.

Addiction Treatment

The tobacco cessation literature (Johnson, Griffiths) is striking for effect size. The NYU alcohol literature (Bogenschutz, Ross) is notable for trial quality. Individual case accounts from participants in these studies describe dramatic shifts in the perceived identity associated with the addictive behaviour — a new sense of self as a non-smoker, or alcohol feeling incompatible with one's values — alongside emotional processing of underlying drivers. Early case reports exist for opioid use disorder, though controlled trial data are limited and should be interpreted cautiously. The severity of opioid use disorder and the availability of medical support significantly affect outcomes.

End-of-Life Anxiety

End-of-life anxiety — existential distress, fear of death, and demoralisation in people facing terminal illness — was among the first indications explored in the modern psilocybin renaissance. Studies by Griffiths et al. (2016) and Ross et al. (2016, Journal of Psychopharmacology) involving over 80 cancer patients in randomised designs showed large effect sizes for reductions in depression and anxiety, with clinically meaningful decreases in death anxiety specifically. Participant accounts describe not the elimination of awareness that death is approaching, but a fundamental change in how they relate to that awareness. Many describe feeling less identified with their bodies and more aware of continuity with something larger — described in spiritual, existential, or philosophical terms depending on individual worldview. Integration in this population benefits from involving family members where the participant is open to this.

OCD

Moreno et al. (2006, Journal of Clinical Psychiatry) administered psilocybin to nine adults with treatment-resistant OCD in an open-label design with four dose conditions. All nine showed marked, dose-dependent reductions in OCD symptoms (Yale-Brown Obsessive Compulsive Scale); improvements were observed even at sub-psychedelic doses and lasted beyond the acute drug effects. No serious adverse events occurred. Proposed mechanisms involve 5-HT2A receptor activity in habit formation circuits and psilocybin's promotion of cognitive flexibility disrupting rigid thought patterns. Individual case accounts from the OCD community describe changed relationships with obsessive thoughts — viewing them as less urgent, less real, or less threatening. Larger controlled trials are needed and are underway.

PTSD

PTSD is an emerging indication with multiple open-label trials now underway. Case accounts describe experiences in which traumatic memories surfaced with reduced emotional charge — "seeing the memory without being in it" — a quality consistent with the reconsolidation model of trauma treatment. Veterans with combat-related PTSD and moral injury are represented in community case accounts, with descriptions of experiences involving forgiveness, compassion, and shifted sense of responsibility. Challenges include the risk that psilocybin's effects on emotional processing can temporarily worsen hyperarousal without adequate support — making trauma-informed facilitation essential. See Research Case Studies for current trial status.

Microdosing Outcomes

The microdosing case literature is primarily observational and self-report. Szigeti et al. (2021, eLife) conducted a self-blinded citizen-science study finding that although expectancy explained much of the reported benefit, genuine pharmacological effects on wellbeing and psychopathology were detected at a population level. Case accounts range from reported improvements in creativity, focus, and emotional regulation to accounts of increased anxiety, emotional volatility, and perceptual disturbance with more frequent dosing. Negative experiences in the microdosing context are underrepresented due to reporting bias — this library actively seeks submissions documenting both positive and negative outcomes.