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

Abstract

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.

Similar rhythms of seasonal conceptions in neural tube defects and schizophrenia: A hypothesis of oxidant stress and the photoperiod

“…Consistent with this photoperiod hypothesis (but also with a temperature hypothesis), studies of schizophrenia found no seasonal birth effect at the equator (Parker et al, 2000) and, in the northern hemisphere, a stronger effect with increasing latitude (Davies et al, 2003).…”

Estudos traducionais de neuropsiquiatria e esquizofrenia: modelos animais genéticos e de neurodesenvolvimento

“…Maternal immune activation is considered to be an etiological factor in schizophrenia based on epidemiological studies of influenza infection in mothers of schizophrenia patients, and an increased incidence of schizophrenia among winter births [125][126][127] . This has been modelled in rodents by infecting pregnant animals with viruses or by administration of the bacterial endotoxin lipopolysaccharide (LPS).…”

Season of birth and subclinical psychosis: Systematic review and meta-analysis of new and existing data

“…Season of birth (SOB) has been shown to modify risk for several health outcomes, including a number of neuropsychiatric disorders (Brewerton, Dansky, O'Neil, & Kilpatrick, 2012;Cheng et al, 2013;Davies, Welham, Chant, Torrey, & McGrath, 2003;Disanto et al, 2012;Dome, Kapitany, Ignits, & Rihmer, 2010). In effect, there is evidence indicating that seasonality influences fetal growth and development (Currie & Schwandt, 2013;Flouris, Spiropoulos, Sakellariou, & Koutedakis, 2009;Strand, Barnett, & Tong, 2011;Watson & McDonald, 2007), which bears significance for psychiatric research.…”