Integrating the Mystical Experience Questionnaire Into a Broader Psychometric Framework: English Validation of the Psychedelic Experience Scale and Comparison of Psilocybin and LSD Sessions Across Two Controlled Settings

Summary

The Psychedelic Experience Scale (PES48) has an eight-factor structure that includes the well-validated Mystical Experience Questionnaire (MEQ30) plus four additional factors: paradoxicality, connectedness, visual experience, and distressing experience. This study tested whether the full eight-factor structure is valid in English, using data from 280 PES measurements from 145 healthy participants in four placebo-controlled psilocybin studies. Six of the eight subscales showed high internal consistency, one good, and one acceptable. Confirmatory factor analysis indicated acceptable to good model fits for the MEQ30 and MEQ40, with English data showing better fits than the German validation sample. The findings suggest the PES48 is a valid psychometric tool in English, enabling broader measurement of mystical and non-mystical aspects of psychedelic experience.

Study at a glance

Abstract

Objectives: For English, the validated part of Psychedelic Experience Scale (PES48) is a four-factor structure called the Mystical Experience Questionnaire (MEQ30). The other validated part of the PES48 consists of four more factors: two more mystical factors (paradoxicality and connectedness, which together with the MEQ30 form the MEQ40), and two more non-mystical factors (visual experience and distressing experience). However, this latter four-factor part of the PES48 has thus far only been validated for the German version of the PES48. We investigated whether the overall eight-factor structure of the PES48 (which includes the MEQ30 four-factor structure) can also be validated, and thus potentially be put to good use in English. Methods: Data from 280 English PES measurements (145 different healthy participants) from four placebo-controlled studies with low to high doses of psilocybin were included. The reliability of the eight subscales was evaluated using measures of internal consistency. The validity of the factor structure was assessed through model fit indices from confirmatory factor analysis. English results were then also compared with the German PES validation data set from Stocker et al. (2024). Results: Six of the eight subscales (mystical, positive mood, transcendence of time and space, ineffability, connectedness, distressing experience) of the English PES48 show high internal consistency, one subscale (paradoxicality) shows good, and one (visual experience) acceptable internal consistency. Both MEQ models (MEQ30 and MEQ40) show similar fits (acceptable to good model fits). In English, both MEQ models show better fits than in German. All six MEQ40 scale means of the English data are higher compared to German data. Conclusions: The findings suggest that the eight-factor PES48 is also a valid psychometric tool in English. With the MEQ40 part of the PES48, one can measure mystical experience with a still wider conceptual breath than with the MEQ30. Furthermore, one can also measure non-mystical visual and distressing states in an overall more comprehensive and broader conceptualization of the psychedelic experience. Higher MEQ40 scale means for the English than the German study participants could inspire future research into the role of setting in relation to mystical experience.