Development of the Japanese version of the 30-item Mystical Experience Questionnaire

Psychedelics have garnered increased attention as potential therapeutic options for various mental illnesses. Previous studies reported that psychedelics cause psychoactive effects through mystical experiences induced by these substances, including an altered state of consciousness. While this phenomenon is commonly assessed by the Mystical Experiences Questionnaire (MEQ30), a Japanese version of the MEQ30 has not been available. The aim of this study was to develop the Japanese version of the MEQ30.

We adhered to the "Principles of Good Practice for the Translation and Cultural Adaptation Process for Patient-Reported Outcomes (PRO) Measures: Report of the ISPOR Task Force for Translation and Cultural Adaptation" in our translation process. Two Japanese psychiatrists independently performed forward translations, from which a unified version was derived through reconciliation. This version was subsequently back-translated into English and reviewed by the original authors for equivalency. The iterative revision process was carried out through ongoing discussions with the original authors until they approved the final back-translated version.

The final, approved back-translated version of the MEQ30 is presented in the accompanying figure. Additionally, the authorized Japanese version of the MEQ30 is included in the Appendix A.

In this study, we successfully developed a Japanese version of the MEQ30. This scale will facilitate the assessment of mystical experiences associated with psychedelic-assisted therapy among Japanese speakers. Further research is warranted to evaluate the reliability and validity of this newly translated scale.