Seasonality effects on schizophrenic births in multiplex families in a tropical island

Psychiatry Research
Jose R Carrión-BaraltJeremy M Silverman

Abstract

Many studies have found that individuals with schizophrenia have been born in winter months in disproportionately high numbers. Temperature and weather effects, such as hot summers or cold winters, have been among the suggested explanations for this seasonality effect. We studied the relationship between schizophrenia and season of birth in Puerto Rico, a tropical island with mild seasonal variation of temperature and virtually no cold periods. Our sample consisted of 132 subjects (57 with schizophrenia, 75 without) from 24 multiplex families. Schizophrenic family members were significantly more likely to be born during the winter months (21/57; 36.8%) than their unaffected relatives (16/75; 21.3%). These results suggest that extreme temperatures are not a sufficient explanation for the seasonality effect and that other factors associated with seasonality may have an effect on the later development of schizophrenia. The fact that a seasonality effect was found in a group likely to have an increased genetic loading for schizophrenia suggests that seasonality may be associated with a second, environmental "hit" in a "two-hit hypothesis" of schizophrenia.

References

Apr 1, 1981·Acta Psychiatrica Scandinavica·E Hare, P Moran
Jan 15, 1998·Schizophrenia Research·E F TorreyR H Yolken
May 2, 2000·The British Journal of Psychiatry : the Journal of Mental Science·G ParkerD Machin
Apr 11, 2001·Schizophrenia Research·E L de MessiasB Kirkpatrick

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Citations

Jan 7, 2011·Journal of Psychiatric Research·Alex S Cohen, Gina M Najolia
Aug 30, 2008·Medical Hypotheses·George E Davis, Walter E Lowell
Aug 28, 2007·The Psychiatric Clinics of North America·Erick L MessiasWilliam W Eaton
Sep 3, 2013·Psychiatry and Clinical Neurosciences·Chin ChengTsuo-Hung Lan

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