[Depression in schizophrenia: diagnosis, epidemiology, predisposing factors].
The observation and debates concerning the coexistence of depression and schizophrenia date  back to Kraepelin and Bleuler. Both recognized that among the basic symptoms of 'dementia praecox' and "schizophrenia", are the flattening of affect and the depressed affect and both included in  their clinical descriptions of schizophrenia the depressive symptoms. During the recent years this  observation has been made official, with the inclusion of diagnoses like schizoaffective psychosis  as well as the post psychotic or post schizophrenic depression in the international disease categorization  systems  DSM  and  ICD.  Several  theories  have  been  proposed  to  explain  the  relation  of  depression and schizophrenia, especially when there both appear simultaneously in the same patient.  Depression can be present during the prepsychotic prodromal phase, during the acute phase or  after the remission of the psychotic features. In addition depressive symptoms could be part of the  clinical picture of chronic stabilized patients. Depression in schizophrenia is defined in different  ways, i.e. through the criteria of DSM and ICD, through the relevant items of psychopathological  scales or through the total rating of depression scales if the score exceeds a certain cut-off. Since  the existing depression scales have been created to evaluate depressed patients and therefore  there were questions of validity of their use in schizophrenic patients, recently it has been proposed  a special scale to evaluate depression specifically in schizophrenic patients (Calgary Depression  Scale for Schizophrenia). This scale has been standardized in a Greek sample. In general, according to the existing studies 7-70% of all schizophrenic patients suffer from some form of clinically  relevant depression and the median frequency from all the available studies is 25%. The frequency  of depression in new schizophrenic patients is 21-24% during the acute phase and it seems that  this frequency progressively decreases with the time and stabilizes around 8% in remitted patients.  These frequencies may vary upwards depending on the definition of depression. One in four schizophrenic patients with depression presents with suicide ideation and therefore requires appropriate  identification and management. As far as predisposing factors for the appearance of depression  concerns, the existing data are inadequate and contradictory to extract safe conclusions and therefore further research is in line.
1st Department of Psychiatry, University of Athens, Medical School, Eginition Hospital, Athens, Greece.
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