Validation of the Japanese version of the Patient Health Questionnaire-4 (PHQ-4-J) to screen for depression and anxiety.

Objective: We aimed to validate the Japanese version of the Patient Health Questionnaire-4 (PHQ-4-J). People in Japan, especially healthcare workers (HCWs) suffer from high rates of mental health symptoms. The PHQ-4 is an established ultra-brief mental health measure used in various settings, populations and languages. The Japanese version of the PHQ-4 has not been validated.

Methods: Two hundred eighty people in Japan (142 HCWs and 138 from the general public) responded to the PHQ-4-J. Internal consistency, and factorial validity were assessed using confirmatory factor analysis (CFA) and Multiple Indicators Multiple Causes (MIMIC) models.

Results: Internal consistency was high (α = 0.70-0.86). CFA yielded very good fit indices for a two-factor solution (RMSEA = 0.04, 95% CI 0.00-0.17) and MIMIC models indicated the performance differed between HCWs and the general population.

Conclusions: The PHQ-4-J is a reliable ultra-brief scale for depression and anxiety in Japanese, which can be used to meet current needs in mental health research and practice in Japan. Disaster research and gerontology research can benefit from this scale, enabling mental health assessment with little participant burden. In practice, early detection and personalised care can be facilitated by using the scale. Future research should target specific populations in Japan during a non-emergency time.