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    subjective effects hallucinogens psychedelics study ICEERS ayahuasca

    Measuring the Subjective Effects of Hallucinogens


    Measuring the subjective: revisiting the psychometric properties of three rating scales that assess the acute effects of hallucinogens

    José Carlos Bouso, Eduardo José Pedrero-Pérez, Sam Gandy, and Miguel Ángel Alcázar-Córcoles.

    Human Psychopharmacology


    About the study

    The subjective effects of psychedelic drugs are probably their most difficult aspect to measure. Therefore, we used novel psychometric data for the MEQ, HRS, and ARCI questionnaires, proposing preliminary new versions and/or alternative interpretations of the data.

    The questionnaires were administered to a sample of 158 subjects after their participation in ayahuasca ceremonies throughout different parts of Spain. The questionnaires were completed after the end of the ayahuasca ceremony and in the same facilities where it took place.

    This paper proposes a preliminary factor structure for three of the most widely used rating scales in the psychopharmacology of psychedelics. This may allow future researchers to measure the subjective effects of psychedelic drugs in a more confident and precise way.



    Objective: In the present study we explored the psychometric properties of three widely used questionnaires to assess the subjective effects of hallucinogens: the Hallucinogen Rating Scale (HRS), the Mystical Experience Questionnaire (MEQ), and the Addiction Research Center Inventory (ARCI).

    Methods: These three questionnaires were administered to a sample of 158 subjects (100 men) after taking ayahuasca, a hallucinogen whose main active component is N,N-dimethyltryptamine (DMT). A confirmatory factorial study was conducted to check the adjustment of previous data obtained via theoretical proposals. When this was not possible, we used an exploratory factor analysis without restrictions, based on tetrachoric and polychoric matrices and correlations.

    Results: Our results sparsely match the theoretical proposals of the authors, perhaps because previous studies have not always employed psychometric methods appropriate to the data obtained. However, these data should be considered preliminary, pending larger samples to confirm or reject the proposed structures obtained.

    Conclusions: It is crucial that instruments of sufficiently precise measurement are utilized to make sense of the information obtained in the study of the subjective effects of psychedelic drugs.


    Link to the article

    Photo by Greg Rakozy on Unsplash.

    Categories: Studies & papers , Ayahuasca , Psychedelics
    Tags: ayahuasca , scientific research , study , psychoactive , psychedelics , hallucinogens , psychometrics