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Autism Spectrum Disorders Health Center

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Risk of Autism Recurrence Higher Than Thought

Study Finds About 19% Risk of Autism in Younger Siblings of Children With the Disorder
WebMD Health News
Reviewed by Laura J. Martin, MD

Aug. 15, 2011 -- The risk of autism in a child whose older sibling has been diagnosed with the disorder is higher than previously believed, according to new research.

Autism and autism spectrum disorders, a group of developmental disorders that affect the ability to think, communicate, and socially interact, affect one in 110 U.S. children, according to the CDC.

In the past, the risk of an autism spectrum disorder occurring in a younger brother or sister was estimated to be from 3% to 14%. However, researchers have now found it is close to 19%.

"The average risk for the whole sample was 18.7%,'' says researcher Sally Ozonoff, PhD, professor of psychiatry and behavioral sciences at the MIND Institute at the University of California, Davis.

Certain children had an even higher risk, she says. ''Families who had male infants had a higher recurrence of 26.2%," she tells WebMD. ''Families that had more than one child with autism prior to the birth of this infant [in the study] had almost a one in three risk, or 32%."

"Overall we found this almost 1 in 5 risk, but more like 1 in 4 if the new baby was a boy and 1 in 3 if the family has more than one child with autism."

The study is published in Pediatrics.

Autism Sibling Risk: Practical Matters

"This was very sad," Ozonoff says of the new estimate. "It brought tears to our eyes for many of us."

However, she says, the information is valuable. Parents can ask for close monitoring of a young sibling. That way, if autism is detected, early intervention can begin. The new information may also help parents in their family planning decisions.

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