Journal Article

A Systematic Review and Meta-analysis of Northern Hemisphere Season of Birth Studies in Schizophrenia

Geoffrey Davies, Joy Welham, David Chant, E. Fuller Torrey and John McGrath

in Schizophrenia Bulletin

Published on behalf of Maryland Psychiatric Research Center

Volume 29, issue 3, pages 587-593
Published in print January 2003 | ISSN: 0586-7614
Published online January 2003 | e-ISSN: 1745-1701 | DOI:
A Systematic Review and Meta-analysis of Northern Hemisphere Season of Birth Studies in Schizophrenia

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Based on the epidemiological finding that individuals with schizophrenia tend to be born in winter/spring when compared to the general population, we examined (1) the strength and timing of this effect in Northern Hemisphere sites, and (2) the correlation between the season of birth effect size and latitude. Studies were located via electronic data sources, published citations, and letters to authors. Inclusion criteria were that studies specify the diagnostic criteria used, that studies specify the counts of schizophrenia and general population births for each month, and that subjects and the general population be drawn from the same birth years and catchment area. We extracted data from eight studies based on 126,196 patients with schizophrenia and 86,605,807 general population births and drawn from 27 Northern Hemisphere sites. Comparing winter/spring versus summer/autumn births, we found a significant excess for winter/spring births (pooled odds ratio = 1.07; 95% confidence interval 1.05, 1.08; population attributable risk = 3.3%). There was a small but significant positive correlation between the odds ratios for the season of birth comparison and latitude (r = 0.271, p < 0.005). Furthermore, the shape of the seasonality in schizophrenia births varied by latitude band. These variations may encourage researchers to generate candidate seasonally fluctuating exposures.

Keywords: Schizophrenia; epidemiology; season of birth; latitude

Journal Article.  0 words. 

Subjects: Child and Adolescent Psychiatry

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