[Depression scales in schizophrenia: a critical review]

Depressive syndromes frequently occur during the evolution of schizophrenia. The evaluation of depression in schizophrenic patients is difficult because of an overlap between depressive, negative and extrapyramidal symptoms. The scales usually employed to evaluate depression have not been validated in schizophrenic populations, therefore, some authors developed specific depression scales for schizophrenics. In this work, we present the available data about the metrologic and psychometric properties of the Hamilton (HDRS), Montgomery Asberg (MADRS) and Widlöcher (ERD) depression scales in schizophrenic populations. We further present the validation works of the Psychotic Depression Scale (PDS) and the Calgary Depression Scale (CDSS). Non specific depression scales are unsatisfactory, since negative and extrapyramidal symptoms overlap with depressive symptoms. The ERD allows a distinction of the three symptom groups, when motor, ideic and subjective subscores are used. The two specific scales actually distinguish depression with a minimal level of contamination. Nevertheless, the factorial structure of the PDS comprises several non depressive factors that are of questionable interest. The CDSS is a well documented and validated tool, with an unidimensional structure, a good internal consistency, a high inter-rater reliability, and good external validity and specificity.