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28-12-2011 | Psychology | Article

High birthweight associated with increased risk for schizophrenia

Abstract

Free abstract

MedWire News: Infants with a high birthweight (HBW) are nearly twice as likely to develop schizophrenia than those born with a normal weight, show study findings.

The results are at odds with findings showing an association between low birthweight (LBW) and schizophrenia, but are in agreement with four previous studies.

"Our results strengthen previous findings implicating HBW as a possible risk factor in the development of schizophrenia and reflect a possible need to shift emphasis to the examination of both extremes of birthweight with respect to schizophrenia susceptibility," say Asko Wegelius (National Institute for Health and Welfare, Helsinki, Finland) and colleagues.

To investigate the association between birthweight and schizophrenia, the team analyzed birthweight data from 1051 children from 315 Finnish families with at least one child with a confirmed diagnosis of schizophrenia.

In addition, the association of maternal Type 2 diabetes and schizophrenia risk among children was assessed, using information from the Medication Reimbursement Register and patient interviews.

Survival curves showed that birthweights of 2500-2999 g and 3000-4000 g followed similar risk trajectories, but HBW (>4000 g) was associated with an increased risk for developing schizophrenia. The survival curve representing LBW (<2500 g) followed a trajectory between that of the HBW and intermediate birth weight ranges in both the schizophrenia and primary psychotic disorder groups.

After adjusting for birthweight, gender, and maternal and paternal history of psychotic disorder the researchers found that HBW was associated with a 1.68-fold increased risk for developing schizophrenia. No significant association between HBW and primary psychotic disorder was observed.

Furthermore, no significant association was seen between LBW and schizophrenia or primary psychotic disorder.

Analysis of children with mothers who had diabetes showed similar birthweights compared with those whose mothers did not have the condition. However, a significant association was seen between maternal diabetes and both schizophrenia (hazard rate ratio [HRR]=1.66) and primary psychotic disorder (HRR=1.55) was observed.

No significant association between maternal diabetes and psychotic disorders other than schizophrenia was observed following exclusion of patients with primary psychotic disorder. There was also no association between maternal diabetes and HBW.

"The fact that HBW or maternal diabetes was not associated with an increase in susceptibility to psychotic disorders other than schizophrenia could… support the notion of partly separate etiological mechanisms underlying schizophrenia and non-schizophrenic psychotic disorders," write the authors in the journal Psychiatry Research.

By Ingrid Grasmo

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