Abstract

Background: For one century, psychedelics have been carrying a paradoxical history. On the one hand, they have been examined as a psychosis model for sharing a similar neurophenomenology with psychotic experiences. On the other hand, they have been utilized as a therapeutic model for treating depression, anxiety and substance use disorders. This study sought to explore this paradoxical relationship by investigating the effects of LSD on basic parameters related to psychotic experiences and psychotherapy and connecting them to the psychedelic experience.

Methods: In a randomized, double‐blind, placebo‐controlled, crossover design, 24 healthy volunteers received a low dose of 50μg lysergic acid diethylamide ﴾LSD﴿ or inactive placebo. The psychotic experience was assessed by self‐reported aberrant salience ﴾Aberrant Salience Inventory, ASI﴿, the therapeutic potential by a suggestibility task ﴾Creative Imagination Scale, CIS﴿ and mindfulness questionnaires ﴾Five Facet Mindfulness Questionnaire, FFMQ; Mindful Attention Awareness Scale, MAAS; Experiences Questionnaire, EQ﴿ and the psychedelic experience by several questionnaires ﴾Altered State of Consciousness Questionnaire, ASC; Mystical Experiences Questionnaire, MEQ; Challenging Experiences Questionnaire, CEQ; Ego‐Dissolution Inventory, EDI﴿. Correlations between LSD‐induced effects were examined.

Results: The low dose of LSD induced profound psychedelic experiences, including alterations of consciousness, mystical experiences and, to a lesser extent, ego‐dissolution and challenging experiences. LSD, compared to placebo, increased aberrant salience and suggestibility but not mindfulness. LSD‐induced aberrant salience correlated highly with ego‐dissolution, experience of unity, complex imagery and mystical experiences. LSD‐induced suggestibility correlated with no other effects. Individual LSD‐induced changes in mindfulness correlated moderately with aberrant salience and psychedelic experience.

Conclusions: Low psychedelic doses are poorly explored in modern research but might exert remarkable effects. The results indicate that a low dose of LSD induces a psychotic‐like experience and offers a tool for healing. The link between psychosis model and therapeutic model seems to lie in mystical and ego‐dissolution experiences. The results point to the importance of meaning attribution for the LSD psychosis model and indicate that psychedelic‐assisted psychotherapy might benefit from therapeutic suggestions fostering mystical experiences.