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

Abstract

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. 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. There was a medium decline in somatic symptom burden for the complete sample (n=55, dz=0.53) and a large decline in a subgroup with very high somatic symptom burden at baseline (n=11, dz=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. 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.