Relationship between schizoaffective illness and affective disorders or schizophrenia. Morbidity risk and genetic transmission.

Schizoaffective illness has either been linked to schizophrenia and to affective disorders, or it has been considered to be as separate entity. Family and linkage studies can provide data regarding genetic factors in the aetiology of schizoaffective illness. Morbidity risks for affective illnesses and schizophrenia were estimated in the first-degree relatives of schizoaffective probands as compared to matched controls (bipolars, unipolars and schizophrenics). Linkage studies with X-chromosome markers (protanopia and deuteranopia) were also performed in informative families. Our genetic results indicate that schizoaffective illness is a heterogeneous entity. This syndrome appears to be primarily related to the affective disorders, but there may be a subgroup linked to the schizophrenic spectrum disorders. Our studies also indicate that some schizoaffective syndromes may be transmitted through the X-chromosome, a pattern previously demonstrated in some families with bipolar manic-depressive illness.