Effects of psilocybin on personality, psychiatric symptoms, and values: Exploring mediating effects of the acute psychedelic experience

A single dose of psilocybin, compared to an inert placebo, did not alter personality traits, psychiatric symptoms, or cognitive flexibility in healthy participants. However, both the 10 mg and 25 mg psilocybin groups reported greater changes in personal values at both short-term (day 8) and long-term follow-up (day 85). The acute psychedelic experience, particularly the feeling of oceanic boundlessness, partially explained these value changes, with auditory alterations also playing a role in one subscale. These exploratory findings are tentative and require replication in larger samples.

Study at a glance

Abstract

Background: Changes in well-being, personality, and personal values have been documented post-psilocybin; however, evidence from placebo-controlled trials is limited. Aims: To examine the effects of psilocybin versus placebo on psychiatric symptoms, personality, and personal values in healthy participants. Potential mediators were also explored. Methods: This secondary analysis used data from a phase I, double-blind, randomised, placebo-controlled trial testing a single dose of 10 mg ( n = 30) or 25 mg psilocybin ( n = 30) versus an inert placebo ( n = 29) in 89 healthy participants. Effects of psilocybin on personality (Neo Five-Factor Inventory; NEO-FFI), psychiatric symptoms (Symptom Checklist-90; SCL-90), and values (Life Changes Inventory; LCI) at short- (day 8) and long-term follow-up (day 85) were analysed using mixed-effects models. Group differences in cognitive flexibility (Intra-Extra Dimensional Set Shift task; IED) at day 8 were analysed using a Kruskal–Wallis test. Potential mediating effects of the acute psychedelic experience (Five-Dimensional Altered States of Consciousness Questionnaire; 5D-ASC) were explored. Results: No between-group differences were found on the NEO-FFI, SCL-90, or IED. Both psilocybin groups showed greater LCI absolute change scores at both follow-up points compared to placebo. The 5D-ASC oceanic boundlessness subscale partially mediated these changes. Oceanic boundlessness also fully or partially mediated differences across several LCI subscales, and auditory alterations mediated differences on one subscale. Conclusions: The acute psychedelic experience, namely oceanic boundlessness and, to a lesser extent, auditory alterations, mediates self-reported changes in values in healthy volunteers. Findings from this exploratory study are tentative and should be replicated in larger samples.