Language delays found in siblings of children with autism

October 1, 2010

his graph tracks the symptoms of girls in one category of families affected by autism. Yellow denotes girls with histories of language delay and autistic traits who were never formally diagnosed as having an autism spectrum disorder (ASD). Blue represents unaffected girls, red represents those diagnosed with ASD. Credit: Image courtesy of The American Journal of Psychiatry. Copyright © 2010 American Psychiatric Association. Used with permission.

Siblings of children with autism have more frequent language delays and other subtle characteristics of the disorder than previously understood. Girls also may be mildly affected more often than recognized in the past.

A new study, led by researchers at Washington University School of Medicine in St. Louis, found mild traits, not strong enough to provoke a diagnosis of autism, seem to be present in the siblings of affected children at significantly higher rates than seen in the general population. The findings appear online and will be published in the November issue of The American Journal of Psychiatry.

"Mild symptoms, called quantitative traits, may be confounding studies that compare children with autism to their siblings," says first author John N. Constantino, MD. "Researchers presume one child is affected, and the other is not, but our findings suggest that although one child may have autism while the other does not, it's very possible both children are affected to some degree by genes that contribute to autism."

Genetic factors exert their influence in different ways. Some families have only a single child with autism and no other affected children. But in other families, more than one child may be affected, or other siblings may have a number of autism characteristics.

Siblings of children with autism have more frequent language delays and other subtle characteristics of the disorder than previously understood. Girls also may be mildly affected more often than recognized in the past, according to a new study, led by researchers at Washington University School of Medicine in St. Louis. Credit: Washington University BioMed Radio

The study found that approximately one in five siblings thought to be unaffected experienced language delays or speech problems early in life. The researchers also noticed many female siblings had subtle traits, but few had full-blown autism spectrum disorders. Boys are thought to be affected four times more often than girls. But when the researchers used standardized methods to account for the presence of quantitative traits, the rate looked more like three affected boys for every two affected girls.

"The gender difference may not be as pronounced as we once thought it was," Constantino says. "If we rely only on a professional diagnosis of autism to determine who is affected, then boys vastly outnumber girls. But it may be that many girls are being missed."

The data comes from almost 3,000 U.S. children in 1,235 families who are part of the Interactive Autism Network, a national online research registry athttp://www.IANproject.org. Developed by study co-author Paul Law, MD, director of medical informatics at Kennedy Krieger Institute in Baltimore, the network has more than 35,000 participants who share information to help advance autism research.

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