Season of birth and schizophrenia in Tasmania

Objective: The purpose of the present study was to determine whether there was a significant seasonal variation in the birth dates of patients with schizophrenia born in Tasmania. Method: The season of birth in Tasmanian-born patients with schizophrenia (n = 1412), born between 1919-1970, was compared with general population data. Results: No significant variation in month or quarter of birth was detected for the subjects with schizophrenia. Neither was there any significant seasonal excess when data from different decades were analysed separately, nor for subsidiary analyses of gender or paranoid/non paranoid subtype. Conclusion: These results are compared with those of six other published studies of Australasian-born subjects identified through registers in different States. While both positive and negative results are reported, no clear pattern emerges. The relevance of season of birth to the development of schizophrenia in Australia remains an open question.