Reproductive behaviour in schizophrenia relative to other mental disorders: evidence for increased fertility in men despite decreased marital rate.

Using case register data, the overall marital rate among 5158 patients with mental illness was found to be comparable to the general population. The proportion of those ever married was markedly reduced in the schizophrenic group relative to those with a manic or neurotic illness. Men with schizophrenia had a particularly low rate of marriage. The overall marital fertility of the 3 groups was comparable to each other and appeared to be higher than that in the general population. In the schizophrenic group only, married men, particularly those with a family history of mental disorder, produced more children than married women. Men might represent a more fertile group of schizophrenic patients with some biological advantage of increased fecundity, which may help to compensate for negative selection pressures.