Developing a comprehensive scale for measuring explanatory models of mental disorders among Japanese adults.

Introduction: Individuals differ in their understanding of the causes of illnesses or problems and the appropriate methods for addressing them. Mental disorders can be interpreted from multiple perspectives shaped by cultural backgrounds and personal experiences. The conceptual framework through which individuals recognize and interpret illnesses or problems is referred to as an explanatory model. This study aimed to develop the Explanatory Model Scale for Mental Disorders (EMS-MD), based on Haslam's (2003) explanatory styles-"Medicalizing," "Moralizing," and "Psychologizing"-with the addition of "Socializing" and "Spiritualizing," and to examine its reliability and validity among Japanese adults. Methods: An online survey was administered to 928 Japanese adults aged 18 years and older using five mental disorder vignettes (depression, schizophrenia, alcohol use disorder, anorexia nervosa, and social anxiety disorder). A split-sample approach was used to conduct exploratory and confirmatory factor analyses. Internal consistency, test-retest reliability, convergent and discriminant validity, and measurement invariance across gender and vignette contexts were also examined. Results: The analyses suggested a 24-item, 6-factor structure comprising "Socializing," "Spiritualizing," "Biologizing," "Medicalizing," "Moralizing," and "Psychologizing." Notably, "Biologizing" and "Medicalizing" emerged as distinct factors, although this distinction was exploratory because both had originally been conceptualized as part of a broader "Medicalizing" category. Most subscales demonstrated adequate internal consistency, and all exhibited good test-retest reliability. However, "Psychologizing" showed low internal consistency, indicating that this subscale should be interpreted cautiously and requires further item refinement of its item pool. Correlations with measures of the Attribution of Responsibility Process and the Japanese Health Locus of Control subscales were generally consistent with predictions, providing preliminary evidence for convergent validity. The Fornell-Larcker criterion provided preliminary evidence for discriminant validity. Multigroup analyses indicated that the measurement structure was generally stable across gender; however, measurement invariance across vignette contexts was limited. Discussion: Overall, the EMS-MD shows promise as a preliminary measure of explanatory styles for mental disorders among Japanese adults. Nevertheless, limitations related to model fit, the internal consistency of "Psychologizing," and measurement equivalence across vignettes highlight the need for further item refinement and validation in other cultural contexts.