Monitoring somatic symptoms in patients with mental disorders: Sensitivity to change and minimal clinically important difference of the Somatic Symptom Scale-8 (SSS-8)

Objective: The SSS-8 is a brief questionnaire for the assessment of somatic symptom burden. This study examines its sensitivity to change and the minimal clinically important difference (MCID) in patients with mental disorders. Method: 55 outpatients with mental disorders completed the SSS-8 and measures of anxiety, depression, and disability before and after receiving treatment. Effect sizes and correlations between the change scores were calculated. The MCID was estimated using a one standard error of measurement threshold and the change in disability as an external criterion. Results: There was a medium decline in somatic symptom burden for the complete sample (n = 55, d(z) = 0.53) and a large decline in a subgroup with very high somatic symptom burden at baseline (n = 11, d(z)=0.94). Decreases in somatic symptom burden were associated with decreases in anxiety (r = 0.68, p < 0.001), depression (r = 0.62, p < 0.001) and disability (r = 0.51, p < 0.001). The MCID was estimated as a 3-point decrease. Conclusion: The SSS-8 is sensitive to change. A 3-point decrease reflects a clinically important improvement. Due to its brevity and sound psychometric properties, the SSS-8 is useful for monitoring somatic symptom burden.