Rapid Effects of MDMA Administration on Self-Reported Personality Traits and Affect State: A Randomized, Placebo-Controlled Trial in Healthy Adults

Introduction

Maples-Keller and colleagues situate their study within growing interest in MDMA as a psychotherapeutic adjunct and a literature on serotonergic psychedelics producing lasting changes in personality and affect. Earlier research has shown that classic psychedelics (for example, psilocybin and LSD) can increase Five-Factor Model (FFM) Openness and sometimes decrease Neuroticism or increase Extraversion, often assessed months to a year after administration. By contrast, controlled trials specifically testing MDMA’s effects on personality and affect in healthy adults are limited; much prior work has relied on cross-sectional comparisons of recreational users and non-users or clinical samples receiving psychotherapy alongside drug administration, leaving uncertainty about MDMA’s independent, short-term impact on trait and state measures. This pre-registered, secondary analysis tests whether a single 100 mg dose of MDMA, administered in a randomised, placebo-controlled laboratory trial of psychiatrically and medically healthy adults (N = 34), produces rapid changes in FFM domains and affective state at approximately 48 hours post-administration. The investigators specified four directional hypotheses: MDMA (versus placebo) would produce greater decreases in Neuroticism and Negative Affect, and greater increases in Openness and Positive Affect. The study aims to characterise short-term personality and affective shifts that could plausibly operate as mechanisms in MDMA-assisted psychotherapy and to provide effect-size estimates for future work.