INTRODUCTION: The renewal of psychedelic medicine has garnered significant scientific interest, with large efforts dedicated to the understanding of the complex subjective experiences induced by these substances. The Altered States of Consciousness (ASC) questionnaire represents the most comprehensive instrument for measuring such experiences yet lacks a validated French translation despite its centrality to research.
MATERIALS AND METHODS: A psychometric validation of the French 5D-ASC and 11 OAV subscales was conducted using data from 777 participants recruited through online platforms. Participants completed the 94-item questionnaire based on a past naturalistic psychedelic experience induced by a classical or non-classical psychedelic substance. Confirmatory factor analysis (CFA) of established factorial structures, multiple-indicator multiple-cause (MIMIC) modeling assessing measurement invariance across substance categories, and comprehensive reliability analyses were used.
RESULTS: The 11-subscale solution demonstrated better fit compared to higher-order structures (CFI = 0.882, RMSEA = 0.051, SRMR = 0.061), though comparative fit indices remained marginally below conventional thresholds. Internal consistency was excellent for global scores (α = 0.95) and satisfactory across individual subscales (α = 0.63-0.84). Construct validity was supported by theoretically consistent inter-scale correlations and convergent validity with single-item validators. MIMIC modeling revealed modest differential item functioning but confirmed measurement invariance, with latent factor differences aligning with known pharmacological profiles.
CONCLUSION: This study provides preliminary evidence for the psychometric validity of the French 5D-ASC. These findings enable future research examining the relationship between subjective experience and therapeutic outcomes in francophone contexts, contributing to the international standardization of psychedelic research instruments.
