CHILDREN of women who contract flu during the first months of pregnancy are more likely to develop schizophrenia later in life, scientists have discovered.

Research in the United States has provided the strongest evidence yet for the theory that schizophrenia is often linked to prenatal exposure to the influenza virus.

The findings, from a team at Columbia University in New York, will bring fresh calls for flu vaccinations to be offered routinely to women of child-bearing age, though scientists behind the study cautioned that it was too soon to recommend such a step.

Many experts have long suspected a link between flu infections during pregnancy and some cases of schizophrenia. Studies have shown a higher incidence of the illness in children born after flu epidemics.

Though genetic factors and unknown environmental causes are also thought to influence schizophrenia risk, it is widely thought that prenatal flu is responsible for at least a subset of cases of the disease.

The new study, led by Alan Brown, has demonstrated this link more conclusively than has previously been possible. He found that maternal flu infections during the first half of pregnancy appeared to triple a child’s risk of schizophrenia, though infection in the later stages of pregnancy did not have an adverse effect.

The findings, details of which are published today in the journal Archives of General Psychiatry, suggest that the influenza virus could be responsible for up to one in seven cases of schizophrenia.

Dr Brown’s team used data from a large cohort study known as the Child Health and Development Study. This recruited more than 12,000 people born between 1959 and 1966 and followed them up for mental health problems.

The researchers examined 64 people who went on to develop schizophrenia, and compared them with a matched control sample of 125 who did not. When blood serum samples taken from their mothers while pregnant were analysed for traces of the influenza virus, a strong link was found between raised flu antibody levels and later schizophrenia.

“It is an exciting time for research that combines serologic documentation of infectious diseases during pregnancy, long-term follow-up, and careful assessments for schizophrenia and other disease outcomes,” Dr Brown said.

“Because the individuals who we are studying have only recently passed through the age of risk for schizophrenia, it has become possible only in the past few years to analyse archived prenatal serum specimens (to determine) whether schizophrenia is related to prenatal risk factors such as viruses, as well as nutritional factors and toxins.”

His colleague Ezra Susser said: “These findings represent the strongest evidence thus far that prenatal exposure to influenza plays a role in schizophrenia. Although the findings may ultimately have implications for prevention, we strongly caution against making any public health policy recommendations until these links have been confirmed.”

Dr Brown said that if the findings were replicated, there could be evidence for giving the flu vaccine to women of childbearing age, though he cautioned that giving the vaccine to pregnant women could be harmful.

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