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New Clues to Autism's Causes

By Rod Graham

In the quest to better understand autism, researchers have come a step closer toward teasing out a genetic cause. Babies whose parents have a history of schizophrenia are twice as likely to go on to develop autism as babies whose parents don't have the mental illness, according to researchers at the Bloomberg School, Aarhus University in Denmark, and the Centers for Disease Control and Prevention.

The researchers also confirmed that several factors linked to less-than-optimal births—including breech presentations, low birthweights and low Apgar scores—were also associated with increased risk of autism.

"This is the largest case-control study ever conducted, and the first to suggest that family history of schizophrenia raises risk for autism, independently of obstetric factors," says William W. Eaton, PhD, study co-author and chair of Mental Health.

While previous autism studies used relatively small sample sizes, says Eaton, this one utilized Denmark's extensive database for tracking the health of residents. Researchers examined data on 698 children who were born after 1972 and discharged from Danish psychiatric hospitals or specialty clinics after a diagnosis of infantile or atypical autism through November 1999. The scientists also obtained information on the children's parents.

"Now that we know there's a genetic susceptibility, we have to ask whether the baby is programmed at conception for autism and whether this genetic programming causes the obstetric complications," says Craig Newschaffer, PhD, SM, associate professor of Epidemiology and director of the School's Center for Autism and Developmental Disabilities Epidemiology.

Eaton says the study, published in the May issue of the American Journal of Epidemiology, is just a step toward establishing a genetic cause of autism.

"The Holy Grail, of course," says Newschaffer, "is to find the risk gene or genes [for autism]." Once scientists have located that, they can begin to isolate the disorder's non-genetic causes.