Development of Japanese version of King's Stigma Scale and its short version: Psychometric properties of a self-stigma measure.

AIM The study aimed to develop two Japanese versions of King's Stigma Scale, a full version (KSS-J-1) and a short version (KSS-J-2), through psychometric property testing. METHODS The sample included 112 people with mental illness. We tested the constructs of the scales using both confirmatory and exploratory factor analyses. Internal consistency and test-retest reliability were tested. We examined convergent validity with self-esteem or perceived stigma, and different group validity, using the Kessler Psychological Distress Scale (K6). RESULTS Whereas a relatively weak model fit (comparative fit index = 0.66, Tucker-Lewis index = 0.63, root mean square error of approximation = 0.097) of KSS-J-1 (full version: 28 items) was found, KSS-J-2 (short version: 17 items), produced by exploratory factor analysis, had a moderate model fit (comparative fit index = 0.90, Tucker-Lewis index = 0.89, root mean square error of approximation = 0.063). High internal consistency (KSS-J-1, ω = 0.82-0.89; KSS-J-2, ω = 0.86-0.89) and moderate test-retest reliability (KSS-J-1, interclass correlation = 0.56-0.88; KSS-J-2, interclass correlation = 0.45-0.85) were reported. Some subscales and the entire scale of KSS-J-1 were significantly correlated with self-esteem and perceived stigma. Conversely, only two subscales in KSS-J-2 were significantly correlated with self-esteem. The scores of each subscale and the entire score for both KSS-J-1 and KSS-J-2 in the high psychological distress group were higher than the low group (KSS-J-1, d = 0.61-0.83; KSS-J-2, d = 0.47-0.70), except for the Discrimination subscale in KSS-J-2. CONCLUSION Both Japanese versions of King's Stigma Scale can be utilized depending on their intended use.