Season of Birth: Schizophernia and Bipolar Disorder

Abstract

Studies investigating the association between the risk of schizophrenia and season of birth are reviewed and the association clearly established. This association cannot be explained on the basis of age-incidence or age-prevalence artifacts. Other studies suggest there may be an association between bipolar disorder and season of birth. The leading theory in explaining the season of birth phenomenon is that a seasonal factor (such as viral infection, malnutrition, vitamin deficiency, prenatal or obstetrical complications, or ambient temperature) can damage an infant's brain and thereby predispose the child to later development of psychosis. Evidence suggests that the seasonal effect is associated with a subgroup of schizophrenics who have early onset of psychosis, less genetic loading than other schizophrenics, and better prognosis. Case-control studies are needed comparing winterborn to nonwinter-born schizophrenics.

Seasonal variation of nutrient intake in pregnancy: effects on infant measures and possible influence on diseases related to season of birth

“…A connection has been made between schizophrenia and winter birth. Evidence for this comes from studies in both the northern and southern hemispheres including Oceania (Boyd et al, 1986;McGrath and Welham, 1999). If this disease is influenced by maternal nutrient intake, we speculate that the period of fetal risk is most likely the last months of brain development before birth when folate intake levels are low, and not the embryonic and early fetal period when the gross structure of the central nervous system is developing as nutrient intake levels are at their highest at this stage.…”

“…There is substantial evidence associating winter birth with increased risk of non-deficit or type I schizophrenia, which makes up around 85% of cases (Boyd et al, 1986;Gallagher et al, 1999;McGrath and Welham, 1999;Mortenson et al, 1999;Messias et al, 2004). There is some evidence that those born autumn have the lowest risk of developing multiple sclerosis, whereas those born in spring have an increased risk (James, 1995;Willer et al, 2005).…”

Female gender but not season of birth is associated with mood seasonality in a near-equatorial Brazilian city

“…Previous research has reported a statistically significant influence of season of birth on factors such as brain tumour development 1 , handedness 2 , longevity 3 , personality 4 , and schizophrenia and bipolar disorder 5 . Does season of birth also have an influence on mood?…”

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“…Over the past few years birth patterns of patients with organic and psychiatric disorders have been studied extensively (e.g., Boyd, Pulver, & Stewart, 1986;Dalèn, 1975). The rationale behind this research is as follows: identifying specific birth patterns for disorders may lead to the detection of seasonal environmental factors that contribute to the etiology of these disorders (see Barak, Ring, Sulkes, Gabbay, & Elizur, 1995).…”

“…Schizophrenia is a case in point. It has been found consistently that the incidence of schizophrenia is higher in persons born in the winter months than in those born during the rest of the year (e.g., Boyd et al, 1986;McGrath, Welham, & Pemberton;1995). Seasonality phenomena have also been reported for patients with congenital disorders such as Down syndrome (Harlap, 1974;Jongbloet & Vrieze, Relatively few studies have looked at birth patterns of autistic patients.…”