m-DASC: Measuring Subjective Effects of Very Low Doses of Psychedelic Drugs

Background: There has been great interest in the use of very low doses of psychedelic drugs like lysergic acid diethylamide (LSD) to improve mood and cognition. However, controlled studies have thus far provided little support for their efficacy. One challenge is that the subjective effects are subtle and on the threshold of detectability, whereas the questionnaires used to assess the drugs’ effects were designed for very high, psychedelic doses. Using confirmatory factor analyses, we showed that both the Five-Dimensional Altered States of Consciousness Questionnaire (5D-ASC) and the 11-factor Altered States of Consciousness Rating Scale do not represent the underlying structure of responses to very low doses of LSD. Methods: To address this gap, we conducted a principal component analysis to identify items from previous questionnaires suited to low doses, using data from 199 healthy volunteers who received 6.5, 13, and 26 µg doses of LSD under controlled conditions. Using items from the 5D-ASC, we developed the micro -dimensional Altered States of Consciousness (m-DASC), consisting of four components corresponding to Transcendent Experience, Auditory Somatic Disturbance, Animated Intoxication, and Synesthesia. Results: The m-DASC is substantially shorter than existing questionnaires (31 items). It accounted for 44% of the variance in the dataset used, showed significant effects of LSD at the 26 and 13 µg doses, and was highly correlated with the original longer questionnaires. Conclusions: The m-DASC is likely to be of value in future studies investigating the subjective effects of very low doses of psychedelic drugs.