Latitude, climate and winter birth

How is latitude, climate and winter birth relevant to schizophrenia?

For some time, researchers have observed variations in population rates of schizophrenia, with rates changing depending on the time and place of birth. For example, the prevalence rate in a given population may be increased if birth was at a higher latitude with a cooler climate. These variables are also related to variances in diet, precipitation, sun exposure, socioeconomic status and genetic factors, as well as age and gender differences. Therefore the observed relationships between rates of schizophrenia and higher latitude and cooler climates may have several related explanations.

What is the evidence for latitude, climate and winter birth?

Moderate to high quality evidence finds a small relationship between winter/spring births and increased risk for schizophrenia in the Northern Hemisphere. High quality evidence also finds a small relationship between winter/spring births and subclinical psychotic symptoms in children in Japan and the U.K.

Moderate quality evidence finds a small effect of increased prevalence of schizophrenia with increased latitude and decreased annual mean daily temperature in the Northern Hemisphere. Incidence rates were increased only for males. Moderate to low quality evidence finds this association is greatest in people with older fathers at birth (over 45 years old), and in disadvantaged ethnic minority groups.

Moderate to high quality evidence finds a small effect of increased rates of deficit schizophrenia (predominately negative symptoms) in offspring born in the summer months of June and July in the Northern Hemisphere.

March 2019

Last updated at: 5:18 am, 16th March 2019
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