Adverse reactions among psychedelic users: Norwegian validation of the Challenging Experience Questionnaire

Kristoffer A A Andersen; Bjørn Holmøy; Tor-Morten Kvam; Matthew W Johnson

doi:10.1016/j.jpsychires.2025.05.062

Adverse reactions among psychedelic users: Norwegian validation of the Challenging Experience Questionnaire

J Psychiatr Res. 2025 May 26:189:18-25. doi: 10.1016/j.jpsychires.2025.05.062. Online ahead of print.

Authors

Kristoffer A A Andersen¹, Bjørn Holmøy², Tor-Morten Kvam³, Matthew W Johnson⁴

Affiliations

¹ Section for Clinical Addiction Research, Division of Mental Health and Addiction, Oslo University Hospital, Norway. Electronic address: kranan@ous-hf.no.
² Division of Clinical Mental Health and Addiction, Akershus University Hospital, Norway.
³ Institute of Clinical Medicine, University of Oslo, Oslo, Norway; Nordre Østfold DPS, Østfold Hospital Trust, Grålum, Norway.
⁴ Sheppard Pratt Center of Excellence for Psilocybin Research and Treatment, MD, USA.

PMID: 40466556
DOI: 10.1016/j.jpsychires.2025.05.062

Abstract

Psychedelic drugs, known for their potent psychoactive effects, have gained attention for their potential therapeutic benefits in treating mental disorders. However, distressing experiences induced by psychedelics can lead to adverse long-term effects. To better assess these experiences, we aimed to provide a Norwegian translation and psychometric validation of the Challenging Experience Questionnaire (CEQ), a key tool for evaluating adverse psychedelic experiences. Our study employed an anonymous online survey targeting Norwegian recreational psychedelic users, focusing on their most memorable psychedelic encounter. A sample of 729 participants, predominantly male (73 %) and aged between 26 and 35 years (41 %), with 90 % having used LSD or psilocybin, was analyzed. Half of the participants had completed a university degree, and 48 % reported a diagnosed mental disorder. The CEQ underwent a rigorous seven-stage translation process and was included in the survey to validate the original 7-factor structure. Our findings revealed excellent internal consistency (alpha = 0.94) and robust overall model fit (χ²[278] = 1451.80, RMSEA = 0.076, SRMR = 0.051, CFI = 0.913) for the 7-factor model, with evidence of factorial invariance across gender and psychiatric status. Further, the relationship between reported difficulty and CEQ factors such as fear, grief, insanity, and death underscored its convergent validity. In conclusion, our study confirms the 7-factor structure of the CEQ while demonstrating its reliability and validity. This provides Norwegian researchers with a culturally adapted, psychometrically valid tool for assessing complex adverse reactions to psychedelic use.

Keywords: Bad trip; CEQ; Challenging experiences Questionnaire; Norwegian; Psychedelic; Psychometric.