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Number of older siblings of individuals diagnosed with schizophrenia

C McDonald1, E O'Callaghan, F Keogh

  • 1Cluain Mhuire Family Centre, Newtownpark Avenue, Blackrock, County Dublin, Ireland.

Schizophrenia Research
|March 30, 2001
PubMed

Insights

This study investigated if more older siblings increase schizophrenia risk, particularly in urban or spring births. The findings indicate that the number of older siblings does not predict schizophrenia risk or interact with urban or seasonal birth factors.

Area of Science:

  • Neuroscience
  • Epidemiology
  • Psychiatry

Background:

  • Schizophrenia research consistently shows a slight excess of births in late winter/early spring.
  • Schizophrenia is also linked to urban birth and later birth order.
  • A hypothesis suggests viral infections in crowded households may disrupt fetal brain development, increasing schizophrenia risk.

Purpose of the Study:

  • To test if individuals with schizophrenia and more older siblings are more likely to be born in urban areas and during late winter/early spring.
  • To explore potential interactions between sibling number, urban birth, and season of birth in schizophrenia etiology.

Main Methods:

  • Utilized case register data from Dublin and Three County for 2969 schizophrenia patients and 5904 neurosis patients.
  • Employed logistic regression to analyze the association between the number of older siblings and schizophrenia diagnosis.
  • Controlled for gender, urban/rural birth, season of birth, and sibship size to assess interactions.

Main Results:

  • The number of older siblings did not predict a schizophrenia diagnosis compared to neurosis.
  • No significant interaction was found between the number of older siblings and urban birth.
  • No significant interaction was observed between the number of older siblings and spring birth, or combined factors.

Conclusions:

  • The study's data do not support the hypothesis that schizophrenia is associated with a higher number of older siblings.
  • The findings do not support an interaction between sibling number, urban birth, and season of birth in the context of schizophrenia.
  • This research does not corroborate the proposed link between household viral infections, sibling number, and schizophrenia risk.

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