Abstract
BACKGROUND: The Symptom Checklist-90 (SCL-90) is a questionnaire that is widely used to measure subjective psychopathology. In this study we investigated the psychometric properties of the SCL-90 among adolescent inpatients and community youth matched on age and gender. METHODS: The final SCL-90 respondents comprised three subsets: 201 inpatients at admission, of whom 152 also completed the instrument at discharge, and 197 controls. The mean age at baseline was 15.0 years (SD 1.2), and 73 % were female. Differential SCL-90 item functioning between the three subsets was assessed with an iterative algorithm, and the presence of multidimensionality was assessed with a number of methods. Confirmatory factor analyses for ordinal items compared three latent factor models: one dimension, nine correlated dimensions, and a one-plus-nine bifactor model. Sensitivity to change was assessed with the bifactor model's general factor scores at admission and discharge. The accuracy of this factor in detecting the need for treatment used, as a gold standard, psychiatric diagnoses based on clinical records and the Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime (K-SADS-PL) interview. RESULTS: Item measurement properties were largely invariant across subsets under the unidimensional model, with standardized factor scores at admission being 0.04 higher than at discharge and 0.06 higher than those of controls. Determination of the empirical number of factors was inconclusive, reflecting a strong main factor and some multidimensionality. The unidimensional factor model had very good fit, but the bifactor model offered an overall improvement, though subfactors accounted for little item variance. The SCL-90s ability to identify those with and without a psychiatric disorder was good (AUC = 83 %, Glass's Δ = 1.4, Cohen's d = 1.1, diagnostic odds ratio 12.5). Scores were also fairly sensitive to change between admission and discharge (AUC 72 %, Cohen's d = 0.8). CONCLUSIONS: The SCL-90 proved mostly unidimensional and showed sufficient item measurement invariance, and is thus a useful tool for screening overall psychopathology in adolescents. It is also applicable as an outcome measure for adolescent psychiatric patients. SCL-90 revealed significant gender differences in subjective psychopathology among both inpatients and community youth.