MONDAY, May 2 (HealthDay News) -- The brains of 4- and 5-year-old children with autism are larger than the brains of normally developing children, and the difference probably occurs several years earlier, a new study suggests.
The finding is a follow-up to earlier research that found the brains of 2-year-olds with autism are larger than those of similarly aged normally developing kids, researchers said.
"Our prior paper found that at age 2, children with autism had brain overgrowth, meaning their brains were larger than the comparison children," said study author Heather Cody Hazlett, an assistant professor in the department of psychiatry at University of North Carolina, Chapel Hill School of Medicine.
"We now know this overgrowth was maintained," Hazlett added. "The children with autism kept having significantly enlarged brains at 4 and 5 years old."
On average, autistic children's brains were 9 percent larger than those of other kids.
In the United States, about 1 in every 110 children has autism, a neurodevelopmental disorder marked by social and communication impairment, according to the U.S. Centers for Disease Control and Prevention. The study is published in the May issue of the Archives of General Psychiatry.
Hazlett and her colleagues did MRIs on 59 children aged 18 to 35 months with an autism spectrum disorder and 38 children who did not have autism. Two years later, about 38 children with an autism spectrum disorder and 21 typically developing kids returned for a follow-up MRI.
Researchers were interested in volume of white matter (the connective tissue of the brain), gray matter (made up of neurons), cortical thickness and brain surface area.
At age 2, autistic kids had a larger total brain volume than non-autistic kids.
Two years later, researchers were able to measure cortical thickness and brain surface area, in add
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