Morbidity Risk of Schizophrenia to Parents and Siblings of Schizophrenic Patients

Abstract
In order to estimate the familial morbidity risk of schizophrenia, parents and siblings in 1,691 inpatients meeting the DSM-III criteria for schizophrenia were investigated on the basis of a review of medical records, family history data and/or personal interviews. The moribidity risks of schizophrenia to parents and siblings of the schizophrenic probands were 4.0% and 4.1%, respectively, which were greater than the morbidity risk in the general population. Siblings of 118 probands whose parents suffered from schizophrenia were at a significantly greater risk of schizophrenia than siblings of 1,493 probands whose parents did not have schizophrenic illness. These findings support the notion of familial transmission of schizophrenia. A total of 16.4% of the schizophrenic probands had at least one first-degree relative with schizophrenia. This is significantly greater in the female probands than in the male probands.