Validation of the revised Mystical Experience Questionnaire in experimental sessions with psilocybin

Abstract

The 30-item revised Mystical Experience Questionnaire (MEQ30) was previously developed within an online survey of mystical-type experiences occasioned by psilocybin-containing mushrooms. The rated experiences occurred on average eight years before completion of the questionnaire. The current paper validates the MEQ30 using data from experimental studies with controlled doses of psilocybin. Data were pooled and analyzed from five laboratory experiments in which participants (n=184) received a moderate to high oral dose of psilocybin (at least 20 mg/70 kg). Results of confirmatory factor analysis demonstrate the reliability and internal validity of the MEQ30. Structural equation models demonstrate the external and convergent validity of the MEQ30 by showing that latent variable scores on the MEQ30 positively predict persisting change in attitudes, behavior, and well-being attributed to experiences with psilocybin while controlling for the contribution of the participant-rated intensity of drug effects. These findings support the use of the MEQ30 as an efficient measure of individual mystical experiences. A method to score a "complete mystical experience" that was used in previous versions of the mystical experience questionnaire is validated in the MEQ30, and a stand-alone version of the MEQ30 is provided for use in future research.

Keywords: Psilocybin; entheogen; factor analysis; hallucinogens; mystical experience; psychedelic; psychometrics; spiritual; structural equation modeling.

Conflict of interest statement

Declaration of Conflicting Interests The authors declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Dr Griffiths is on the board of directors of the Heffter Research Institute, a funding sponsor for some of the studies included in this report.

© The Author(s) 2015.

Figures

Figure 1

Confirmatory factor structure and factor correlations for the four-factor, 30-item Mystical Experience Questionnaire (MEQ30). For each factor loading, 95% confidence intervals were estimated using bootstrapping in the lavaan toolbox in the R statistical package, and are presented in square brackets next to each factor loading. The States of Consciousness Questionnaire (SOCQ) item number and the MEQ30 item number for each item is presented at the end of the text for that item. Factor loadings are standardized.

Figure 2

Retrospective ratings of the spiritual significance of psilocybin sessions are predicted by MEQ30 “mystical” factor scores. Retrospective ratings were provided three to eight weeks after each psilocybin session. MEQ30 ratings were provided seven hours after capsule administration. The line of best fit is plotted through the scatterplot. The standardized regression coefficient (B) from the structural equation model and the associated z- and p-values for this relationship are superimposed on the figure.

Figure 3

Retrospective ratings of psilocybin sessions are predicted by the MEQ-total factor score. Retrospective ratings were provided three to eight weeks after each psilocybin session. MEQ30 ratings were provided seven hours after capsule administration. Lines of best fit are plotted through each scatterplot. Standardized regression coefficients (B) from the structural equation model and their associated z and p values are superimposed on each axis. (A and B) Retrospective ratings of the (A) meaningfulness and (B) spiritual significance of psilocybin sessions are plotted against standardized MEQ30-total scores. (C and D) Retrospective ratings of (C) change in well-being and (D) positive behavior change attributed to psilocybin sessions are plotted against standardized MEQ30-total scores.