Date of Degree


Document Type


Degree Name





Paul Wachtel

Committee Members

Diana Diamond

Steve Tuber

Elliot Jurist

Diana Punales

Subject Categories

Clinical Psychology


psychedelic, hallucinogen, psilocybin, personality


As classic psychedelics are increasingly legalized and reintroduced into the psychotherapeutic frame, a deeper understanding of their effect on personality and overall wellbeing - as well as their clinical contraindications and potential pitfalls - will prove essential. As a result, this study represents a preliminary investigation into the effect of psilocybin exposure on a range of personality constructs.

Methods: Data was collected through a collaboration with The Psychedelic Society, an organization that legally administers psilocybin truffles in the Netherlands to self-selecting retreat attendees who have been screened for mental health disorders in accordance with Johnson et al.’s (2008) widely accepted safety guidelines. Participants completed the following measures via online questionnaire the day before psilocybin exposure, two days after psilocybin exposure, and at a one-month follow-up: Brief Symptom Inventory (BSI), Experiences in Close Relationships-Revised (ECR-R), Mentalization Scale (MentS), Inventory of Personality Organization (IPO), Pathological Narcissism Inventory (PNI), Pro-Environmental Behavior (PEB) and the Ryff Scale of Psychological Well-Being (Ryff). As rigorous double-blind clinical studies have linked psychedelic-occasioned mystical experiences to sustained improvement in personality-related domains (Maclean et al., 2011; Griffiths et al., 2006; Griffiths et al., 2008, Griffiths et al., 2011), the Mystical Experience Questionnaire (MEQ) was also administered. Lastly, participants provided self-report responses to open-ended questions regarding subjective experiences following psilocybin exposure.

Results: Due to the Covid-19 pandemic, data collection was prematurely cut short, and only preliminary conclusions can be drawn. Those provisional conclusions include significantly improved overall symptomatology (BSI GSI), identity diffusion (IPO-ID) and reality testing (IPO-RT) following psilocybin exposure. Significant interactions were also identified for primitive defenses (IPO-PD) and narcissistic grandiosity (PNI-G), with the non-mystical experience group trending toward improvement, and the mystical-experience group remaining largely unchanged over time. Due to methodological constraints encountered, these findings remain preliminary. Nevertheless, the presence of multiple significant findings (however nascent) within the context of so few participants suggests the possibility of more robust findings in the context of a larger sample size.