Validity and sensitivity to change of the Somatic Symptom Disorder-B Criteria Scale (SSD-12) in a clinical population

OBJECTIVE: The SSD-12 is a brief self-report questionnaire to measure the psychological criteria of DSM-5 Somatic Symptom Disorder. This study examines its psychometric properties in a German inpatient sample from a psychosomatic rehabilitation setting, and provides evidence to its sensitivity to change.

METHOD: Patients completed the SSD-12 and the Health49-subscale on somatoform complaints before and after receiving inpatient treatment. Therapists evaluated the psychological improvement of their patients at the end of treatment. Effect sizes (ES) and standardized response means (SRM) of pre- and post-SSD-12 mean changes were calculated for subgroups of patients who did or did not improve.

RESULTS: SSD-12 scores at discharge were significantly lower compared to scores at admission for subgroups of patients who improved according to clinicians (t=2976, df=103, p=.004), and for patients who improved according to self-report (t=5.059, df=159, p<.001). Effect sizes of change in SSD-12 scores in the improved subgroups were ES=-0.19 and ES=-0.30, and standardized response means were SRM=-0.29 and SRM=-0.40, respectively.

CONCLUSION: The SSD-12 shows sound psychometric properties and is useful and time-efficient for monitoring psychological burden associated with bothersome somatic symptoms. Its sensitivity to change over time could be documented.