Season of Birth and Schizophrenia: A Systematic Review and Meta-Analysis of Data From the Southern Hemisphere

SCHIZOPHRENIA:

A SYSTEMATIC REVIEW AND META-ANALYSIS OF DATA FROM THE SOUTHERN

Queensland Centre for Schizophrenia Research

supports an excess of winter-spring births of individuals who

later develop schizophrenia when compared to the general

population. The data from the Southern Hemisphere has been less

consistent. This paper will present a systematic review and

searched electronic databases, reviewed citations from target

publications and wrote letters to published authors in the field.

The counts for observed and expected births were assessed in four

planned comparisons. In the absence of significant heterogeneity,

the data were combined using Mantel-Haenzel odds ratio in a fixed

Published and unpublished data from 8 of these were able to be

included in the analyses. For the two season comparisons (n =

19,349), small but non-significant excesses were found in the

first comparison (winter versus other seasons; OR=1.04, 95% Cl 0

99-1.09) and for the second comparison (winter and spring versus

other seasons; OR=1.03, 95% cl 0.99-1.08). For the two quarterly

comparisons (n=14,799), there was a small but non-significant

excess found in the third comparison (third quarter versus other

quarters; OR=1.03, 95% Cl 0.98-1.09), and a small but

non-significant deficit in the fourth comparison (third and

acts as proxy marker for fluctuating non-genetic risk-modifying

factors for schizophrenia, the results of this review suggest

that in the Southern Hemisphere these factors may be weaker, less

prevalent, less regular, and/or may be modified by other