Reliability and validation of the Japanese version of the somatic symptom disorder-B criteria scale (J-SSD-12)

This study evaluated the reliability and validity of the Japanese version of the Somatic Symptom Disorder-B Criteria Scale (J-SSD-12), which assesses psychological features of somatic symptom disorder (SSD) as defined by the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) Criterion B.

A total of 1148 Japanese internet panel participants completed the J-SSD-12, Patient Health Questionnaire-9 (PHQ-9), Generalized Anxiety Disorder-7 scale (GAD-7), Patient Health Questionnaire-15 (PHQ-15), and Short Health Anxiety Inventory (SHAI). Confirmatory factor analysis (CFA) examined factorial validity, with a correlated error specified between Items 7 and 10 for their shared negative wording and emphasis on others' evaluations. Reliability was assessed using test-retest correlations, intraclass correlation coefficients (ICCs), and Cronbach's alpha (α). Convergent validity was primarily evaluated through correlations with four additional scales.

The mean participant age was 48.8 years (SD = 17.3), and 54.6 % were female. The scree plot and high inter-factor correlations suggested a possible unidimensional structure; however, the one-factor model did not achieve satisfactory fit (Comparative Fit Index [CFI] = 0.94, Root Mean Square Error of Approximation [RMSEA] = 0.107). In contrast, the three-factor structure showed acceptable fit on CFI (0.96) and Tucker-Lewis Index (TLI; 0.95), while RMSEA (0.091) indicated only marginal fit. The J-SSD-12 demonstrated good test-retest reliability (correlation coefficient [r] = 0.72; ICCs = 0.72-0.84) and excellent internal consistency (α = 0.95). Moderate correlations with the PHQ-9, GAD-7, PHQ-15, and SHAI (r = 0.60-0.66) supported convergent validity.

The J-SSD-12 provides evidence supporting the reliability and validity of assessing SSD-related psychological features in a Japanese sample. Despite certain limitations, this measure appears useful for both research and potential clinical applications.