Riassunto dello studio

Twenty-four healthy participants were included in this double-blind, randomized, counterbalanced, cross-over study investigating the effect of lysergic acid diethylamide (LSD) on social influence processing as well as the role of the serotonin system in these processes. Participants received three different combination treatment protocols (placebo plus placebo, placebo plus LSD, Ketanserin plus LSD) across three sessions with a washout period of at least two weeks between sessions. Subjective drug effects were assessed with the Altered States of Consciousness (5D-ASC) and Positive and Negative Affect Schedule (PANAS) questionnaires, and brain scans were obtained using fMRI while participants completed a social influence paradigm. Results reveal that LSD increases social adaptation but only if the opinions of others are similar to the individual’s own. These increases were also associated with increased activity in the medial prefrontal cortex. Additionally, pretreatment with Ketanserin fully blocked LSD-induced changes during feedback processing, indicating a key role of the 5-HT2A system in social feedback processing.