Rhesus Incompatibility As a Risk Factor for Schizophrenia in Male Adults.

Background: Rhesus (Ph) incompatibility is a cause of hemolytic disease of the fetus and newborn. Hemolytic disease results from the transplacentally transmitted maternal antibodies against Rh factor D and can cause permanent neurological damage in the affected newborn. This study examines the hypothesis that Rh incompatibility may be a risk factor for schizophrenia.Methods: A sample of 1867 male subjects was divided into two groups, 535 Rh incompatible and 1332 Rh compatible, and compared on rate of schizophrenia.Results: The rate of schizophrenia was significantly higher in the Rh-incompatible group (2.1%) compared with the Ph-compatible group (0.8%) (P<.03). In addition, since the risk for Ph hemolytic disease increases with second and later Rh incompatible pregnancies, it is noteworthy that the second- and later-born incompatible offspring exhibited a significantly higher rate of schizophrenia than second- and later-born compatible offspring (P<.05). Also, as predicted, the rate of schizophrenia among firstborn incompatible subjects was not significantly different from that of firstborn compatible subjects (1.1% vs 0.7%).Conclusion: Ph incompatibility may be a risk factor for schizophrenia.