Schizoaffective disorder--an ongoing challenge for psychiatric nosology

Schizoaffective disorder is a common diagnosis in mental health services. The present article aims to provide an overview of diagnostic reliability, symptomatology, outcome, neurobiology and treatment of schizoaffective disorder.

Literature was identified by searches in "Medline" and "Cochrane Library".

The diagnosis of schizoaffective disorder has a low reliability. There are marked differences between the current diagnostic systems. With respect to psychopathological symptoms, no clear boundaries were found between schizophrenia, schizoaffective disorder and affective disorders. Common neurobiological factors were found across the traditional diagnostic categories. Schizoaffective disorder according to ICD-10 criteria, but not to DSM-IV criteria, shows a more favorable outcome than schizophrenia. With regard to treatment, only a small and heterogeneous database exists.

Due to the low reliability and questionable validity there is a substantial need for revision and unification of the current diagnostic concepts of schizoaffective disorder. If future diagnostic systems return to Kraepelin's dichotomous classification of non-organic psychosis or adopt a dimensional diagnostic approach, schizoaffective disorder will disappear from the psychiatric nomenclature. A nosological model with multiple diagnostic entities, however, would be compatible with retaining the diagnostic category of schizoaffective disorder.