Gut and chest infections in early childhood appear to raise the risk of developing schizophrenia later in life, Oz scientists reveal.
Their discovery, resulted from the study of the birth and hospital records of more than 40,000 young adults in Western Australia, radically expands links between the psychiatric disorder and physical illness.
According to the study, boys who were admitted to hospital at least twice before age three with respiratory or intestinal infections were 80 per cent more likely than others to develop the disabling mental disorder by the time they were in their mid- to late-20s, the Age reported.
Previous research has shown an association between brain infections, such as meningitis, and schizophrenia, but the Curtin University study is the first to demonstrate a link with illnesses that rarely involve the central nervous system - suggesting widespread inflammation, and the body's response to it, may be sufficient to disrupt brain development.
Study leader Wenbin Liang, from the university's National Drug Research Institute, said young children's immature immune systems meant viruses could more readily affect the brain, and such infections did not always show symptoms.
The blood-brain barrier, which prevents bacteria and other foreign bodies from passing from the blood into the fluid surrounding the brain, developed more slowly in some children, Dr Liang wrote in the journal Psychiatry Research, and these individuals' brains might be more susceptible to inflammation caused by infection elsewhere in the body.
Colin Binns, a professor of public health at the university, who was not involved with the study, said the results emphasised the importance of breastfeeding.
"Early infections are more common in non-breastfed infants. Breastmilk contains ... compounds essential for brain development," he said.
Vaughan Carr, chief executive of the Schizophrenia Research Institute and professor of psychiatry at the University of New South Wales, said, "it could be the [gut and lung] infections may reflect some compromise in the immune status of the individual".
Professor Carr said immune disorders had been linked to schizophrenia, which affects one in 200 people, and evidence was emerging for a common genetic origin of both.