The SCL-90 factor structure in comorbid substance abusers

Previous research has shown that the SCL-90 predicts response to treatment by substance abusers. However, the construct validity of the subscales has been questioned. The present study assessed the factor structure of the SCL-90 in 740 outpatients with coexisting substance use and nonsubstance use psychiatric disorders. The congruency coefficient and salient similarity index tested factorial invariance across gender. Exploratory factor analyses assessed the scale's empirical factor structure. The pattern of loadings for the first three factors was congruent in each gender. The factor analysis yielded three inter-correlated factors that together accounted for 38% of the variance in ratings from the entire sample. A single higher-order factor was identified that explained 60% of the variance in factor scores. These findings are consistent with previous studies that obtained a single predominant factor, and suggest that the SCL-90 primarily taps general psychiatric distress in comorbid substance abusers.