Calgary Depression Scale for Schizophrenia: a study of the validity of a French-language version in a population of schizophrenic patients.

The Calgary Depression Scale for Schizophrenia (CDSS) is a nine-item structured interview scale developed by Addington et al. to assess depression in schizophrenics. This paper describes the testing of the reliability and validity of the French version of the CDSS in a population of 70 schizophrenic patients. The validity of the CDSS as a measure of depression was confirmed; a single factor accounted for 41% of the variance of the nine items. The total score on the CDSS was strongly correlated with those on the Montgomery-Asberg Depression Rating Scale (MADRS), the Hamilton Depression Rating Scale (HDRS) and also the G6 item (depression) of the Positive and Negative Syndrome Scale (PANSS). The correlation with the Psychomotor Retardation Scale (ERD) total score was much less significant and was better with the 'subjective' subscore. The internal consistency was good, with a Cronbach's alpha of 0.79. A high level of inter-rater reliability was observed (weighted kappa values were >0.75 in all cases). The CDSS has a lower stability over time than other depression scales. It is a simple, quick and reliable scale for assessing depression in schizophrenic populations.