Does schizoaffective disorder really exist? A systematic review of the studies that compared schizoaffective disorder with schizophrenia or mood disorders.

BACKGROUND: Since its first definition in the literature, schizoaffective disorder (SAD) has raised a considerable controversy regarding its clinical distinction from schizophrenia (SCH) and mood disorders (MD) as well as its validity as an independent nosological category.
OBJECTIVE: Investigate the validity of SAD as a discrete nosological category and its relationship with SCH and MD.
METHOD: A systematic literature review of clinical trial that compared SAD with SCH and/or MD patients was carried out throughout MEDLINE, psycINFO, Cochrane Library, SCIELO and LILACS databases.
RESULTS: Evaluation of demographic characteristics, symptomatology, other clinical data, dexamethasone suppression test, neuroimage exams, response to treatment, evolution and family morbidity indicated that SAD occupies an intermediate position between SCH and MD. Literature review also failed to indicate a clear cut distinction between SAD and SCH or MD. DISCUSSION: Present analysis indicated that SAD cannot be interpreted as atypical forms of SCH or MD. SAD also does not appear to represent a SCH and MD comorbidity or yet an independent mental disorder. It is argued that SAD might constitute a heterogeneous group composed by both SCH and MD patients or a middle point of a continuum between SCH and MD.