Reliability and validity of the Calgary Depression Scale for Schizophrenia (CDSS) in youth at clinical high risk for psychosis

Abstract

Assessment of depression in individuals who are considered to be at clinical high risk (CHR) for psychosis is important as high rates of depression have been reported in CHR individuals. The Calgary Depression Scale (CDSS) is the most widely used scale for assessing depression in schizophrenia. It has excellent psychometric properties, internal consistency, inter-rater reliability, sensitivity, specificity, and discriminant and convergent validity. The aim of this study was to test the reliability and validity of the CDSS in a sample of youth at CHR for psychosis. Participants were assessed for depression, presence of axis 1 mood disorders, and prodromal symptoms using the CDSS, the Structured Clinical Interview for DSM-IV Disorders (SCID-1), and the Scale of Prodromal Symptoms (SOPS). The CDSS total score as well as all individual items, except “guilty ideas of reference,” were significantly associated with the presence of a major depressive disorder. Significant correlations were observed between CDSS total score and the dysphoric mood item on the SOPS. There was some evidence of overlap between the CDSS and both attenuated positive symptoms and negative symptoms as assessed by the SOPS. It is concluded that CDSS is a reliable scale suitable for assessing depression in individuals considered to be at CHR for psychosis.