MONDAY, May 5 (HealthDay News) -- Parents of children with autism have double the odds of having been hospitalized for a psychiatric condition than parents of children without autism, according to a comprehensive review of Swedish medical registries.

Eventually, the information may provide a way for experts to start untangling the complex genetic and environmental interactions involved in different psychiatric conditions, including autism.

"The study suggests there is no evidence of specific transmission of specific psychiatric disorders -- i.e. schizophrenia, depression and personality disorders -- across generations, but that there is more a complex genetic diathesis, a genetic vulnerability, which increases the risk for autism and perhaps other psychiatric illness mediated by unknown developmental and psychosocial variables that are associated with the 'turning on and off' of certain genes," explained one expert, Dr. Jon Shaw, director of child and adolescent psychiatry at the University of Miami Miller School of Medicine.

"This study might help us pinpoint some more genetic ties to more cases [of autism]," added study lead author Julie Daniels, assistant professor of epidemiology and maternal and child health at the University of North Carolina, in Chapel Hill.

She and her colleagues published their research in the May issue of Pediatrics.

The study was most notable for its size, incorporating data on 1,237 children born in Sweden between 1977 and 2003 who had been diagnosed with autism before the age of 10, as well as about 31,000 controls.

Both mothers and fathers with schizophrenia were roughly twice as likely to have a child with autism, the study found.

Only mothers with depression and neurotic and personality disorders (as opposed to fathers) had an increased risk of having a child diagnosed with autism.

The study confirms previous, smaller studies that found that psychiatric disorders were more common among blood relations of people with autism. A strong genetic component is suspected for autism, a developmental disorder.

"The study . . . will stimulate further research by its suggestion that mental disorders are more complex than our simple-minded categorical approach to diagnosis," Shaw said. "Boundaries between diagnoses are less clear, and we need to take a more developmental approach to our understanding of psychiatric illness if we want to understand their complexities."

"I do think it will help us redefine the case definitions [of autism]," Daniels added.

A second study in the same issue of the journal found that children whose mothers had certain infections during pregnancy (bladder infection, diarrhea, cough or vaginal yeast infection) were more likely to develop epilepsy.

The exact reasons for the association are unclear, said a group of researchers based in Denmark, but there is some evidence to suggest that infections occurring during pregnancy may interfere with fetal brain development.

More information

Visit the U.S. National Institute of Neurological Disorders and Stroke for more on autism.

SOURCES: Jon Shaw, M.D., director and professor, division of child and adolescent psychiatry, University of Miami Miller School of Medicine; Julie L. Daniels, Ph.D., assistant professor, epidemiology and maternal and child health, University of North Carolina, Chapel Hill; May 2008 Pediatrics

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