Dose-response relationships of LSD-induced subjective experiences in humans

Lysergic acid diethylamide (LSD) is a potent classic serotonergic psychedelic, which facilitates a variety of altered states of consciousness. Here we present the first meta-analysis establishing dose-response relationship estimates of the altered experience induced by LSD. Data extracted from articles identified by a systematic literature review following PRISMA guidelines were obtained from the Altered States Database. The psychometric data comprised ratings of subjective effects from standardized and validated questionnaires: the Altered States of Consciousness Rating Scale (5D-ASC, 11-ASC) and the Mystical Experience Questionnaire (MEQ30). We performed meta-regression analyses using restricted cubic splines for data from studies with LSD doses of up to 200 g base. Most scales revealed a sigmoid-like increase of effects with a plateauing at around 100 g. The most strongly modulated factors referred to changes in perception and illusory imagination, followed by positively experienced ego-dissolution, while only small effects were found for Anxiety and Dread of Ego Dissolution. The partly observed considerable variability of effects points to the importance of non-pharmacological effects on subjective experiences. The established dose-response relationships may be used as general references for future experimental and clinical research on LSD to relate observed with expected subjective effects and to elucidate phenomenological differences between psychedelics.