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 (χ²/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.