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Risk of schizophrenia and age difference with older siblings. Evidence for a maternal viral infection hypothesis?
P C Sham1, C J MacLean, K S Kendler
1Department of Psychiatry, Institute of Psychiatry, London.
Insights
Maternal viral infections may influence schizophrenia risk. Children with older siblings during gestation showed an increased risk of developing schizophrenia, supporting the viral infection hypothesis.
Area of Science:
- Neuroscience
- Epidemiology
- Genetics
Background:
- Emerging evidence suggests a link between maternal viral infections during pregnancy and an increased risk of schizophrenia in offspring.
- Respiratory viral infections are often transmitted within households by young children, potentially exposing pregnant individuals.
Purpose of the Study:
- To investigate the association between sibling age during gestation and the risk of schizophrenia.
- To test predictions derived from the maternal viral infection hypothesis of schizophrenia etiology.
Main Methods:
- Utilized a Swedish family study dataset.
- Analyzed the relationship between birth order, sibling age during gestation, and schizophrenia risk.
- Controlled for potential confounders including sibship size.
Main Results:
- A decreased risk of schizophrenia was observed in first-born children.
- Individuals with siblings aged three to four years during gestation exhibited a significantly increased risk of schizophrenia.
- Findings remained significant after adjusting for birth order and sibship size.
Conclusions:
- Results provide indirect support for the maternal viral infection hypothesis for schizophrenia.
- The observed associations suggest that exposure to siblings during prenatal development may influence schizophrenia risk.
- Further research is needed to confirm these findings and explore alternative explanations.
Abstract:
Recent reports that some influenza epidemics may be followed by a transient increase in the births of schizophrenic patients have led to the hypothesis that maternal viral infections contribute to the aetiology of schizophrenia. It is well known that respiratory viral infections are frequently brought into the home by young children. We tested the predictions that the risk of schizophrenia is decreased in first-born children, and increased in individuals who had siblings of a young age while in utero, using data from a Swedish family study. Our results are consistent with these predictions. In particular, having siblings three to four years older was associated with a significantly increased risk of schizophrenia, even after allowing for birth order, sibship size, and other potential confounders. If replicated, these results provide indirect support for the maternal viral infection hypothesis, although there are alternative explanations.