Fertility and schizophrenia: evidence for increased fertility in the relatives of schizophrenic patients.

Fertility has been observed to be reduced in patients with schizophrenia, although the disorder was seen to occur at a steady rate in the general population. The hypothesis of increased fertility in the healthy relatives of the patients, which maintained the genetic contribution to the disorder has been proposed but has not received much support. The present study reports the fertility rate in 100 schizophrenic patients and their relatives (grandparents, parents, uncles, aunts and siblings). The fertility of the different family members was compared, taking into account the completion of age of maximum reproductivity, i.e. up to 50 years of age. The trends in fertility rates over three generations of patients' families were compared with those in the general population of India over a corresponding period from 1950 to 2000 AD. The patients were observed to be hypofertile, but their parents showed a higher fertility than all other relatives, as well as the general population. The siblings of the patients also tended to have higher fertility rates than the general population. This increased fertility in parents and sibs, who are the probable carriers of the abnormal gene, could compensate for the reduction in genetic contribution to morbid risk for schizophrenia due to reduced reproductivity of the patients themselves.