Psychometric comparison of the Calgary Depression Scale for Schizophrenia and the Hamilton Depression Rating Scale

This study compared two measures of depression in a population with schizophrenia. Inpatients (n=112) with schizophrenia, were assessed on the Hamilton (HDRS), and Calgary (CDSS) depression scales and the Positive and Negative Syndrome Scale (PANSS). Eighty-nine were reassessed 3 months later. A principal components factor analysis was applied to each depression scale. The relationship between measures of depression and positive and negative symptoms was explored using correlation, factor and regression analyses. There were no significant correlations between the total CDSS and positive or negative symptoms at either time. In contrast, the HDRS total score was correlated with both positive and negative syndromes at time 2. Moreover, a number of HDRS factors correlated significantly with the PANSS positive scale at both times and with the negative subscale score at time 2. Multiple regression analysis showed that the HDRS accounted for more of the variance in positive and negative symptoms scores than did the CDSS. The CDSS has fewer factors and less overlap with positive and negative symptoms than the HDRS. This suggests that it is a more specific measure of level of depression than the HDRS for individuals with schizophrenia.