In the context of the development of DSM-V and ICD-11 it appears to be useful to get further data on the validity of the diagnostic differentiation between schizophrenic and affective disorders. This study investigated the relevance of the main diagnostic groups schizophrenia, schizoaffective psychosis and affective disorder in the context of different diagnostic systems (ICD-9, ICD-10, DSM –IV), assessing their time stability, long-term courses, types and functional outcome.

A total of 323 first hospitalized inpatients of the Psychiatric Department of the University Munich were recruited at index time. The full follow-up evaluation including standardized assessment procedures could be performed in 197 patients.

The re-diagnosis of the patients’ disorders shows that with the transition from ICD-9 to ICD-10 or DSM-IV, the group of affective disorders increased numerically while the diagnostic groups of schizophrenia and schizoaffective disorders decreased in size. The structured clinical interview for DSM-IV (SCID) analysis showed that altogether ICD-10 and DSM-IV had a relatively high diagnostic stability. Of the patients with an ICD-10 diagnosis of schizophrenia, 57% had a chronic course; 61% of the patients with a DSM-IV diagnosis of schizophrenia. Patients with affective disorders, according either to ICD-10 or DSM-IV, had in more than 90% of the cases an episodic-remitting course. In terms of prediction of long-term outcome regarding the differentiation between chronic and non-chronic course, the ICD-10 diagnoses did give a slightly better predictive result than a dimensional approach based on the key psychopathological syndrome scores.

The differentiation between schizophrenic and affective disorders seems meaningful especially under predictive aspects. A dimensional syndromatological description does not exceed the predictive power of the investigated main diagnostic categories, but might increase the clinically relevant information.