Children with autism have larger brains than children without the disorder, and the growth appears to occur before age 2, according to a new study released Monday.
Previous imaging research found differences in the brains of children with autism and those without. It's not clear if autism causes the brain changes or if the changes cause autism, a neurodevelopmental disorder characterized by deficits in social interaction and communication.
A 2005 study by researchers at the University of North Carolina at Chapel Hill found that 2-year-old children with autism have brains up to 10% larger than children without autism. The study compared the brains of 59 children with autism and 38 without autism.
Researchers followed that group and had many of them undergo another magnetic resonance imaging scan when they were 4- or 5-years-old. The study found that children who had enlarged brains at age 2 continued to have enlarged brains at ages 4 and 5, but that the rate of growth hadn't increased compared to brains of children without autism.
This puts researchers closer to figuring out exactly when brain changes start to occur. The study will be published in the May issue of the Archives of General Psychiatry. The study was funded by the National Institutes of Health and the National Alliance for Medical Image Computing.
Researchers believe that increased brain growth appears to start near an infants' first birthday. They note that other studies of infant siblings of individuals with autism show typical social behaviors at age 6 months before the onset of autistic social behavior at 12 months in infants who later meet the criteria for autism.
One of the study authors, Joseph Piven, director of the Carolina Institute for Developmental Disabilities at UNC, said the findings help narrow the scope of additional autism research.
Dr. Piven is currently recruiting patients into another study involving infant siblings of children with an autism diagnosis to see if brain changes can be seen at 6- or 12-months of age. Information on that study can be found at www.ibisnetwork.org.
The increased brain growth was seen in the brain's surface area, or increased folds in the brain, says Piven, rather than an increase in the thickness of outer layer of the brain or what's known as the gray matter.
Autism is typically diagnosed at age 3. Researchers are working to make such diagnoses earlier. A study released last week suggested a questionnaire used during babies' 12-month wellness checkups can help detect autism-like symptoms by identifying potential communication problems.
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