The Afterglow Inventory (AGI) – Validation of A New Instrument for Measur-ing Subacute Effects of Classic Serotonergic Psychedelics

Abstract

Tomislav Majic, Timo Torsten Schmidt, Anna Groticke and Peter Gasser

Background Classic psychedelics such as psilocybin and LSD are anecdotally associated with the phenomenon of "psychedelic afterglow," a set of predominantly pleasant, temporary psychological effects reported after the acute effects have subsided. Since post-acute effects are crucial for the therapeutic use of psychedelics, an instrument to systematically assess subacute "afterglow" effects is needed.

Aims To create and validate a questionnaire to quantify subacute "afterglow" effects of psychedelics.

Methods An international online survey was conducted in English and German. Participants who had consumed a psychedelic (N = 1,323) or another non-psychedelic substance (control group, N = 157) within the past four weeks were included. An initial list of 97 items was progressively reduced to 24 items.

Results A 5-factor structure best fit the data and showed high internal consistency. The factors included 1) Vitality, 2) Transpersonal Aspects, 3) Inspiration/Creativity, 4) Interpersonal Relationships, and 5) Relationship to Nature. The final 24-item version of the Afterglow Inventory (AGI) effectively differentiated between the psychedelic group and the control group. The overall AGI score positively correlated with the intensity (r = 0.165; p < 0.001) and positive valence (r = 0.251; p < 0.001) of the acute psychedelic effects.

Conclusions The AGI is a novel scale for quantifying positive subacute ("afterglow") effects of psychedelics. The use of the AGI could lead to a better understanding of the interplay between acute, subacute, and long-term effects of psychedelics. Insights could also be gained into how different substances, dosages, and extra-pharmacological factors, such as psychotherapy, might influence outcomes.

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