The validity of the symptom checklist depression and anxiety subscales: A general population study in Sweden

The Symptom Checklist (SCL) is used as a screening tool in patient settings, but is also used as a diagnostic proxy for depression and anxiety in public health surveys. However, there are few validation studies based on general population samples. This study aims to validate the SCL subscales for depression and anxiety in a general population sample in Stockholm, Sweden.

We used a stratified random sample answering first a postal questionnaire covering SCL (n=8613) and then a semi-structured psychiatric interview based using Schedules for Clinical Assessment in Neuropsychiatry (SCAN, n=881). Agreement between SCL depression (SCL-DEP) and anxiety (SCL-ANX) scales and their respective DSM-IV disorder was examined by ROC analysis. Discriminant analysis was performed with factor analysis on the SCL depression and anxiety items. The SCL-DEP scale was also compared with the ability of the Major Depression Inventory (MDI) in detecting depressive disorders.

A factor analysis with two factors differentiated the two subscales, with some cross loading items. The SCL-DEP and ANX subscales agreement with depression and anxiety disorders was good. SCL-DEP MDI performed better in detecting DSM-IV depression.

The questionnaire only included the SCL depression, anxiety and hostility subscales and not the full SCL-90. Also, no other anxiety scale was available for comparison.

We conclude that depression and anxiety subscales are suitable instrument for proxies of depression and anxiety disorder in public health surveys.