Psychometric validation of the Hopkins Symptom Checklist (SCL-90) subscales for depression, anxiety, and interpersonal sensitivity

Background: The psychometric validity of many subscales of the 90-item Hopkins Symptom Checklist (SCL-90) remains largely unknown. Therefore, the aim of the present study was to evaluate the psychometric properties of the "Hamilton-subscales" for depression (SCL-D16), anxiety (SCL-A14), their 6-item core-measures (SCL-D6 and SCL-A6), the anxiety symptom scale (SCL-ASS8) and the interpersonal sensitivity scale (IPS5).

Methods: The psychometric properties of the SCL-D16, SCL-A14, SCL-D6, SCL-A6, SCL-ASS8, and the IPS5 were evaluated based on SCL-90 ratings from 850 day patients from a Danish psychiatric day hospital. The factor structure of the SCL-D16 and the SCL-A14 was investigated by means of principal component analysis (PCA) and the unidimensionality of all scales was estimated by Mokken analysis. Finally, the discriminant validity of the scales, i.e. their ability to distinguish between patients with various diagnoses, was tested.

Results: The PCA of the SCL-D16 and the SCL-A14 separated the core depression items from the arousal items on the SCL-D16 and the psychic anxiety items from the somatic anxiety items on the SCL-A14. According to the Mokken analyses, only the SCL-D6, the SCL-ASS8 and the IPS5 were unidimensional. Interestingly, the same three scales displayed discriminant validity for depression, anxiety disorders and personality disorders, respectively.

Limitations: The study is based on data from Denmark. This may limit the validity of the results.

Conclusions: Three unidimensional SCL-90 subscales were identified. Using these scales it is possible to perform a psychometrically valid evaluation of psychiatric patients regarding the severity of depression (HAM-D6), specific anxiety (SCL-ASS8) and interpersonal sensitivity (IPS5).