Prenatal flu exposure and schizophrenia

Some children who are exposed to the flu virus when in the womb have a higher risk of developing schizophrenia later in life.

It's known that schizophrenia is a disorder of disrupted brain development, and researchers have long believed that it arises from a combination of genetic susceptibility and environmental factors. Among the suspected environmental factors is fetal exposure to a mother's infection during pregnancy, with the influenza virus being one of the potential culprits.

Researchers from America compared 111 adults with schizophrenia or other psychotic disorders and 333 healthy adults the same age. All had been part of a larger study of prenatal factors and childhood development begun in 1959; their mothers were followed during pregnancy, and as 7-year-olds, the study participants took standard tests of IQ and cognition.

It was found that schizophrenic adults who had been exposed to the flu virus in the womb tended to have lower scores on IQ tests in childhood, before the onset of psychosis, compared with their peers. In contrast, prenatal influenza exposure seemed to have no impact on childhood IQ among study participants who did not go on to develop schizophrenia.

The effects in the study appeared dependent on the strain of influenza. Only maternal infection with influenza B, and not influenza A, was linked to childhood cognitive performance and later schizophrenia.

The results of the study suggest that decreases in cognitive performance frequently found in children who later develop schizophrenia could be partially attributable to fetal exposure to influenza. However, flu exposure alone does not tell the whole story. It's likely that some other factor associated with schizophrenia - whether that be genes or another environmental exposure - renders the fetal brain vulnerable to damage from the influenza virus.

The findings offer hope that there may be ways to prevent schizophrenia in some cases. Flu vaccination before pregnancy would be one example. In addition, pinning down the various risk factors for the disorder - like prenatal flu exposure and poorer cognitive performance in childhood - may help identify children who are at risk of schizophrenia before symptoms appear. It's not yet clear how to best intervene at that point, however.