Genetic evidence from family, twin, and adoption studies supports classifying schizoaffective psychoses as a separate entity, potentially representing a genetic interform between schizophrenia and affective psychoses.
May support distinct diagnostic classification clinically; leaves open validation with contemporary genomic studies.
The diagnostic classification of schizoaffective psychoses has varied much since Kasanin introduced the concept in 1933. The various classifications have agreed that schizoaffective psychoses present a combination of schizophreniform and affective symptoms, but the diagnostic criteria differ as to the number, quality, and time sequence of the symptoms even in recent classifications like RDC, DSM-III-R, and ICD-10. The classifications are syndromatical, and the etiology of the schizoaffective psychoses is still undetermined apart from evidence for a strong genetic factor. Results from family, twin, and adoption studies are divergent, but all the same, support a separate classification of broadly defined schizoaffective psychoses as possibly being phenotypical variations or expressions of genetic interforms between schizophrenia and affective psychoses.
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Bertelsen et al. (1995) studied this question.
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