Genetic studies of the schizoaffective syndrome: a selective review

The diagnostic validity of the schizoaffective syndrome is assessed from a genetic vantage point. Five studies are reviewed that meet specific methodological requirements. No evidence is provided for the transmission of schizoaffective disorder as a diagnostic entity. The relationship of the schizoaffective syndrome to manic-depressive illness and to schizophrenia is unresolved, and genetic overlap exists between these two disorders in the transmission of the syndrome, with the larger contribution coming from affective disorder, and schizophrenia contributing primarily a severity of illness factor.