Somatic Symptom Scale – 8

Psychometric properties

Internal consistency is supported by a Cronbach's α of 0.81, based on a representative German general population sample. Content validity is considered high because the items derive from the well-validated PHQ-15 and cover the four domains recommended for a valid measure of somatic symptom burden: cardiopulmonary (including autonomic symptoms), gastrointestinal, musculoskeletal, and general symptoms. The SSS-8 shows positive associations with measures of depression and anxiety, consistent with the known comorbidity of somatic, depressive, and anxious symptoms. Higher scores are also linked to poor self-reported general well-being and frequent health care use.

The instrument has a higher order general factor structure with four lower order facets: gastrointestinal symptoms, pain, cardiopulmonary symptoms, and fatigue; this structure is invariant for age and gender. The scoring algorithm is straightforward, and interpretation can be done via severity categories or gender- and age-specific percentiles, contributing to high objectivity. In a sample of patients with mental disorders receiving evidence-based treatment, the SSS-8 demonstrated sensitivity to change, with a decrease of 3 points representing a minimal clinically important difference.