Somatic Symptom Disorder-B criteria scale (SSD-12): Psychometric properties of the French version and associations with health outcomes in a population-based cross-sectional study.

OBJECTIVE:The 12-item Somatic Symptom Disorder-B Criteria Scale (SSD-12) is a self-reported questionnaire designed to assess the B criteria of the DSM-5 somatic symptom disorder. In this cross-sectional study, we aimed to examine the psychometric properties of the SSD-12 French version and associated health outcomes. METHODS:Participants were volunteers from the population-based CONSTANCES cohort who reported at least one new symptom that occurred between March 2020 and January 2021. Depressive symptoms were measured with the Center for Epidemiologic Studies-Depression scale (CES-D). RESULTS:A total of 18,796 participants completed the SSD-12. The scree plot was consistent with a 1-factor structure, while goodness-of-fit indices of the confirmatory factorial analyses and clinical interpretability were consistent with a 3-factor structure (excluding the item 7): 'Perceived severity', 'Perceived impairment', 'Negative expectations'. The Cronbach's α coefficients of the total and factors scores were 0.90, 0.88, 0.84 and 0.877, respectively. The total score was associated with depressive symptoms (Spearmann's rho: 0.32), self-rated health (-0.46), the number of persistent symptoms (0.32), and seeking medical consultation (odds ratio [95% confidence interval] for one interquartile range increase: 1.51 [1.48-1.54]). Among participants seeking medical consultation, those with higher SSD-12 scores were more likely to have their symptoms attributed to "stress/anxiety/depression" (1.32 [1.22-1.43]) and "psychosomatic origin" (1.25 [1.20-1.29]), and less to "COVID-19" (0.89 [0.85-0.93]). CONCLUSION:While the SSD-12 French version can be used as a unidimensional tool, it also has a 3-factor structure, somewhat different from the DSM-5 theoretical structure, with high internal consistency and clinically meaningful associations with other health outcomes.