Development and cross-cultural validation of the Japanese version of the Adjustment Disorder-New Module-20

Adjustment disorder (AjD) is a prevalent mental disorder with evolving definitions in the International Classification of Diseases, 11th Revision (ICD-11). The Adjustment Disorder-New Module-20 (ADNM-20) assesses six AjD symptom clusters based on the ICD-11 criteria and has demonstrated strong psychometric validity. This study aimed to develop and validate a Japanese version of the ADNM-20 in the general population.

A forward-backward translation approach was used to develop the Japanese version of the ADNM-20. Psychometric properties were assessed through a web-based survey of 1314 participants, examining factorial validity, construct validity, and internal consistency.

Confirmatory factor analysis supported the theoretical six-factor model (comparative fit index = 0.923, root-mean-square error of approximation = 0.079), with strong correlations between the ADNM-20 subscales and external measures (e.g., depression PHQ-9, r = 0.71; anxiety GAD-7, r = 0.72). The total ADNM-20 showed excellent internal consistency (Cronbach's α = 0.953).

The Japanese ADNM-20 is a valid and reliable scale for assessing AjD symptoms in the Japanese general population. Further studies involving clinical populations are warranted to confirm its applicability in clinical settings.