Background: The present study investigated the reliability and validity of a Japanese version of the Internalized Stigma of Mental Illness (ISMI) scale, designed to assess internalized stigma experienced by people with mental illness.
Methods: A survey was conducted with 173 outpatients with mental illness who attended psychiatric clinics on a regular basis. A retest was conducted with 51 participants to evaluate the scale's psychometric properties.
Results: The alpha coefficient for the overall internal consistency was 0.91, and the coefficients of the individual ISMI subscales ranged from 0.57 to 0.81. The test-retest reliability was r = 0.85 (n = 51, P < 0.01). In terms of criterion-related validity, the Japanese version of the ISMI scale was significantly correlated with the Beck Depression Inventory (r = 0.61, P < 0.01), the Rosenberg Self-Esteem Scale (r = -0.53, P < 0.01), and the Empowerment Scale (r = -0.52, P < 0.01). In addition, factor analyses of the ISMI items demonstrated a four-factor solution for the alienation, stereotype endorsement, discrimination experience, and social withdrawal subscales, with the stigma resistance items excluded.
Conclusions: The Japanese version of the ISMI scale demonstrated similar reliability and validity to the original English version. Therefore, the Japanese version of the ISMI scale may be an effective and valid tool to measure internalized stigma among Japanese people who have a mental illness.
Keywords: Internalized stigma; Mental disorders; Mental health; Psychometrics; Validation study.