A detailed study of brain samples of children with autism who died young shows remarkably clear changes in their brains, researchers reported on Wednesday.
The differences are seen both on the genetic level and in the physical structure of the brain, and strongly support what scientists have been saying for years that autism starts with disrupted genes that somehow interfere with brain development.
The changes look like patches of arrested development deep in the brain, says Eric Courchesne of the University of California, San Diegos Autism Center of Excellence.
"They are actually jam-packed with brain cells," Courchesne told NBC News. Not only are there too many cells, but they are not developed properly. "Brain cells are there but they havent changed into the kind of cell they are supposed to be. It's a failure of early formation."
It supports the idea that the changes that cause autism are happening in the second and third trimester of pregnancy, Courchesne said.
"Brain cells are there but they havent changed into the kind of cell they are supposed to be. It's a failure of early formation."
But the findings also raise as many questions as they answer about the condition, which has been diagnosed with increasing frequency in the U.S. and elsewhere.
The physical changes suggest that something is causing autism that scientists had not identified before, but they dont shed much light on what that new mechanism might be, Courchesne and colleagues wrote in their report, published in the New England Journal of Medicine.
Autism is becoming more and more common among U.S. kids, and researchers dont quite understand why. The last survey by the Centers for Disease Control and Prevention showed 2 percent of U.S. children have been diagnosed with an autism spectrum disorder, which can range from the relatively mild social awkwardness of Aspergers syndrome to profound mental retardation, debilitating repetitive behaviors and an inability to communicate.
Theres no cure and no good treatment.
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Brain Study Suggests Autism Starts Before Birth