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Human leukocyte antigen and season of birth in Japanese patients with schizophrenia.

OBJECTIVE
Five Japanese studies, to the authors' knowledge, without exception, have consistently shown an increased frequency of human leukocyte antigen (HLA)-DR1 in patients with schizophrenia. This suggests an association between HLA-DR1 and schizophrenia in the Japanese population. The mechanism of the association is unknown; however, prenatal infections may be involved. The present study explored factors, including winter birth, that might correlate with this mechanism. Age at onset and gender were also studied.


METHOD
Factors were compared between Japanese patients with schizophrenia with and in those without HLA-DR1 (N=60 and N=307, respectively).


RESULTS
A significantly higher incidence of births in February and March was observed in patients with (31.7%) than those without (15. 6%) HLA-DR1. No association was found between the presence of HLA-DR1 and other variables.


CONCLUSIONS
Although this result is preliminary, it may suggest an interaction between HLA and winter birth in the development of schizophrenia in the Japanese population.