A review of studies examining the frequency of depression in schizophrenia found prevalence rates ranging from 7% to 75%. This wide range could be reasoned by the in proper selection of the instruments used for assessment.

To answer a question; is there a relation between the used depression scale and the category of schizophrenia and/or depression.

To compare Hamilton (HAMD) and Calgary (CDRS) depression scales in assessing depression in schizophrenia.

385 schizophrenic patients were recruited from Institute of Psychiatry Ain Shams University hospitals and asked to complete Structured Clinical Interview for Diagnosis section for schizophrenia and depression, socio-demographic sheet, medical history sheet, HAMD, CDRS, and Positive and negative Psychotic Symptoms Scale (PANSS).

Depression was found as; disorder (66.2% by HAMD and 39.2% by CDRS), no depression (18.2% by HAMD and 33.2% by CDRS) and symptoms (15.6% by HAMD and 27.5% by CDRS). Agreement of both scales in diagnosing depressive disorder is higher in chronic schizophrenia (62%) than in acute one (50%) and found mostly in continuous and remittent course. No significant correlation was found between CDRS and PANSS scores, while for HAMD, total score for depression was significantly correlated with all psychotic symptoms scores only in schizophrenic patients with depressive disorder.

CDRS is more valid in classification of depression categories in schizophrenia than HAMD. It is more sensitive and specific instrument for assessing depression in schizophrenia than HAMD. However, HAMD may be suitable with acute schizophrenia and remittent course.