Development and validation of the somatic symptom disorder scale: A multicenter study

This study developed and validated the Somatic Symptom Disorder Scale (SSDS) to assess Somatic Symptom Disorder (SSD)–related psychological symptom severity consistent with DSM-5. Psychometric analyses were conducted using three samples: (a) an outpatient clinical group ( N = 314), (b) a matched nonclinical sample for known-groups validity ( N = 80), and (c) a separate nonclinical university sample for test–retest reliability ( N = 73). Reliability, Exploratory Factor Analysis (EFA), Confirmatory Factor Analysis (CFA), and convergent and known-groups validity were evaluated. The SSDS demonstrated excellent internal consistency ( α = 0.94 total; 0.89–0.93 subscales). Test–retest reliability conducted in a nonclinical university sample ( N = 73) indicated strong temporal stability over a two-week interval for the total score ( r = 0.83, p < .001) and the Cognitive ( r = 0.83, p < .001), Affective ( r = 0.77, p < .001), and Behavioral ( r = 0.76, p < .001) subscales. EFA supported a three-factor, 33-item structure, which CFA confirmed with acceptable fit ( χ 2 / df = 2.2, RMSEA = 0.063, CFI = 0.90, SRMR = 0.059). Convergent validity was supported through significant correlations with PHQ-15, PHQ-9, GAD-7, WI-7, and SSAS ( r = 0.32–0.58, p < .001). Known-groups validity indicated that outpatients had significantly higher SSDS scores than nonclinical university students ( t (39) = −8.84, p < .001). The SSDS showed promising reliability and validity for assessing DSM-5–consistent psychological features of SSD. Its overall psychometric properties suggest that it may be useful in both clinical and research contexts. • A new scale was developed to assess DSM-5 Criterion B symptoms of SSD. • The SSDS demonstrated a stable three-factor structure confirmed by EFA and CFA. • The scale showed strong reliability and convergent validity across samples. • Data were obtained from SSD outpatients across multiple clinical settings. • The SSDS provides a brief tool for assessing psychological symptom burden in SSD.