Measurement Invariance of Scores on the Somatic Symptom Scale-8: National Sample of Non-Clinical Adults in the United States.

Objective: The aim of the present study was to test the factorial invariance and convergent validity evidence of scores on the Somatic Symptom Scale (SSS)-8 with a national sample of adults living in the United States.

Method: A data collection contracting service was hired to recruit a national, non-clinical sample ( = 821) of adults in the United States stratified by the census data for age, gender, ethnicity, and geographic location.

Results: Factorial invariance testing via multiple-group confirmatory factor analysis revealed strong factorial invariance evidence (configural, metric, and scalar) of SSS-8 scores across gender, ethnicity, help-seeking history, education, and income.