[Psychometric properties of French version of the Calgary depression scale for schizophrenics (CDSS)]

The Calgary Depression scale for schizophrenia (CDSS) is a 9 items scale, simple, quick and easy to use. It allows a quantitative approach of the subjective (or cognitive) dimension of the depression, and was developed by Addington et al. (1-5). In this work, we studied the psychometric properties of the CDSS in a population of 95 schizophrenic patients, and 41 non schizophrenic depressed patients. The CDSS was compared with commonly used hetero-questionnaires as the Hamilton Depression Scale (HDRS), the Montgomery-Asberg Depression Scale (MADRS), the Widlöcher depressive slowness scale (ERD), and auto-questionnaires as the Beck Depression Inventory (BDI), and the Beck Hopelessness scale (H). In the schizophrenic group, psychotic symptoms were evaluated with the Positive and Negative Symptoms Scale (PANSS), and the extrapyramidal symptoms with the Extrapyramidal symptoms scale (EPRS). In the two populations, the CDSS has similar psychometric properties. The principal component analyses accounts for a unifactorial structure in both groups. In schizophrenics the total score of the CDSS is strongly correlated with the total scores of the HDRS, the MADRS, the ERD, and the G6 item of the PANSS. In non schizophrenic depressed patients, the total score of the CDSS is highly correlated to the total scores of the HDRS, the MADRS and the BDI, with a weaker correlation with the ERD and the H total scores. In these patients, a cut-point strictly superior to 13 may be proposed as a severity criterion for depression in these patients. The internal consistency is satisfactory in both groups, with a Cronbach's alpha of 0.82 in schizophrenics and 0.59 in non schizophrenic depressed subjects. In schizophrenics, items C4 (guilty ideas of reference) and C7 (early awakening) are not necessary to the constitution of the scale. In depressed patients, the deletion of item C6 (morning depression) might increase the internal consistency. Inte-raters agreement is high, with weighted kappas all superior to 0.75 in schizophrenics and to 0.61 in depressed patients. Stability over time is good, and the 72 hours test-retest total score of the CDSS is independent from negative and extrapyramidal symptoms. On the other hand, the positive sub-score and the positive factor of the PANSS are correlated to the CDSS total score. The validation of the CDSS is still not complete: sensitivity to change and stability of the factorial structure remain to be explored. Nevertheless, the CDSS is an interesting tool for a quantitative approach of the subjective dimension of depression in both schizophrenic and non schizophrenic patients.