Morbidity risks of schizophrenia and affective disorders among first-degree relatives of patients with schizoaffective disorders.

Of 510 patients consecutively admitted and diagnosed as schizophrenic, 310 who failed to meet research criteria for schizophrenia were labelled as having 'atypical psychosis'. This heterogeneous group of patients was then subtyped into more homogeneous subgroupings according to their clinical characteristics, independent of their family data. One subgroup resembled schizophrenia, one resembled affective disorders and a third (n = 57), which did not resemble either schizophrenia or affective disorder, was defined as 'schizoaffective'. Comparing the morbidity risks for schizophrenic and affective disorders in the relatives of this schizoaffective group with those of the relatives of 'typical' groups of schizophrenia and affective disorder, showed that this group was different from those with schizophrenic and affective disorders.