Background Lysergic acid diethylamide (LSD) is a potent serotonergic hallucinogen or psychedelic that modulates consciousness in a marked and novel way. This study sought to examine the acute and mid-term psychological effects of LSD in a controlled study. Method A total of 20 healthy volunteers participated in this within-subjects study. Participants received LSD (75 µ g, intravenously) on one...