An investigation of acute physiological and psychological moderators of psychedelic-induced personality change among healthy volunteers.

This study investigated the effects of a single high-dose of psilocybin on personality traits in psychedelic-naïve healthy volunteers. These data originate from a larger within-subjects fixed-order design trial, where a single high dose of psilocybin (25 mg) was administered in a psychologically supportive setting and was compared against a (one-month) prior, 1 mg 'placebo' dose. Personality shifts were assessed by the Big Five Inventory and the Big Five Aspect Scale, while the Altered States of Consciousness questionnaire (5D-ASC) and the Psychological Insight Scale gauged the acute psychological effects of the substance. Electroencephalography provided neurophysiological insights, specifically examining alpha power and Lempel-Ziv complexity (LZc). Results indicated significant reductions in neuroticism one month after 25 mg psilocybin administration, a finding consistent with prior studies. Reductions in neuroticism were moderated by the subjective meaningfulness of the psychedelic experience, as well as by the dread of ego dissolution subscale of the 5D-ASC, suggesting a relationship between acute drug effects and enduring personality alterations. Thus, this study substantiates the role of acute psychedelic states in catalysing lasting personality transformations in a generally beneficial direction, with broader implications for therapeutic applications and understanding of personality dynamics.