Psychometric Validation of the WHO-5 and WHO-4 Well-Being Index Scales for Assessing Psychological Well-Being and Detecting Depression in Japanese School-Aged Children: A Community-Based Study

Masaki Adachi^1*Michio Takahashi²Hiroyuki Mori³Tomoko Nishimura⁴Makoto Osada⁵Minami Adachi⁵Rei Monden⁶Manabu Wakuta⁷Kazuhiko Nakamura⁵

• ¹Meiji Gakuin University, Tokyo, Japan
• ²Tohoku Daigaku, Sendai, Japan
• ³Saitama Gakuen Daigaku, Kawaguchi, Japan
• ⁴Osaka Daigaku, Suita, Japan
• ⁵Hirosaki Daigaku, Hirosaki, Japan
• ⁶Hiroshima Daigaku, Higashihiroshima, Japan
• ⁷Research Department, Institute of Child Developmental Science Research, Hamamatsu, Japan

The 5-item World Health Organization Well-Being Index (WHO-5) is widely used to assess psychological well-being, but its psychometric properties in younger populations, particularly in nonWestern settings, remain underexplored. This study aimed to assess the validity and reliability of the Japanese version of WHO-5 (WHO-5-J) and a culturally adapted four-item version (WHO-4-J), which excludes a culturally sensitive item ("I have felt cheerful and in good spirits") and uses a simplified four-point Likert scale to minimize cognitive burden among Japanese school-aged children. Data were collected from a large community-based sample of 6,983 students aged 10–15 years (Grades 4–9) in Hirosaki City, Japan. Exploratory and confirmatory factor analyses supported the factorial validity and internal consistency of both WHO-5-J (α = 0.84–0.88; ω = 0.86–0.91) and WHO-4-J (α = 0.82–0.88), confirming the unidimensional structures. Multi-group confirmatory factor analyses demonstrated full scalar measurement invariance across age and gender groups. Receiver operating characteristic analyses determined the optimal cutoff scores for detecting psychological distress, with area under the curve values ranging from 0.80 to 0.85, indicating good diagnostic accuracy. Overall, WHO-4-J demonstrated comparable psychometric properties to WHO-5-J, supporting its practical utility as a culturally appropriate tool for assessing psychological well-being and screening for depression in Japanese youth. These findings underscore the importance of cultural adaptation and developmentally appropriate scaling for accurately assessing psychological well-being in diverse, non-Western child populations.