Assessment of the acute subjective psychedelic experience: A review of patient-reported outcome measures in clinical research on classical psychedelics

Classical psychedelics such as psilocybin, peyote, ayahuasca, and LSD can temporarily alter consciousness, affecting perception, mood, and sense of self. Reliable measurement tools are needed because the acute subjective experience may influence treatment outcomes. A review of 93 trials identified 17 different rating scales used to assess these altered states. The five most common instruments were the Five-Dimensional Altered States of Consciousness Questionnaire, visual analog or Likert scales developed for specific trials, the Hallucinogen Rating Scale, the States of Consciousness Questionnaire, and the Abnormer Psychischer Zustand. The authors recommend developing a core set of outcome measures to allow comparisons across different psychedelics, participants, and settings, and suggest designing instruments that assess the setting of the experience.

Study at a glance

Abstract

Background: The classical psychedelics psilocybin, peyote, ayahuasca/ N, N-dimethyltryptamine, and lysergic acid diethylamide can temporarily produce altered states of consciousness, characterized by changes in sensory perception, thought, mood, and the sense of self-reality and meaning. It is important to have reliable instruments for quantifying these altered states in trials, due to a plausible link between the acute subjective experience and treatment outcome. Methods: We conducted a review of outcome measures applied in research on classical psychedelics to assess one or more dimensions of the acute subjective psychedelic experience. Three relevant databases were searched electronically. Two reviewers independently conducted article selection and data extraction regarding the instruments, dimensions, geography, population, and psychedelic substance investigated in the included studies. We identified the five most utilized instruments for the most recent 6 years, as well as the five most utilized instruments for each psychedelic. Results: We included 93 papers, which reported on 93 unique trials and utilized 17 different rating scales. Of these, the most utilized were the Five-Dimensional Altered States of Consciousness Questionnaire, visual analog or Likert scales specially developed for the trials, the Hallucinogen Rating Scale, the States of Consciousness Questionnaire, and the Abnormer Psychischer Zustand. Discussion: Considerable variability was found in the instruments utilized in clinical trials on classical psychedelics. We advise and encourage the development of a core outcome set for psychedelic research to enable altered state comparisons across compounds, participants, and settings. We further advise that instruments be designed to assess the “setting” of a psychedelic experience.