Feb. 17, 2012 -- Differences in brain development may be evident as early as age 6 months in children who go on to develop autism, according to new research.

In the study, children later diagnosed with autism spectrum disorder (ASD) had abnormal development of the white matter in the brain, says researcher Joe Piven, MD, director of the Carolina Institute for Developmental Disabilities at the University of North Carolina, Chapel Hill.

White matter is rich in nerve fibers. It is crucial so the regions of the brain can ''talk'' to each other. This study has found the earliest brain differences in autism, Piven believes.

"There is an aberrant pattern related to autism," he tells WebMD.

"As early as 6 months, the brain of a child who develops autism is organizing itself differently," says researcher Jason Wolff, PhD, a University of North Carolina postdoctoral fellow.

The study is published in the American Journal of Psychiatry.

Autism spectrum disorders are complex developmental brain disorders. ASDs now affect one in 110 U.S. children, according to the CDC. Genetic and environmental factors are blamed. People with the condition have social and behavioral challenges and repetitive behaviors.

Researchers are trying to find early clues of ASD, before symptoms develop.

Slideshow: A Visual Guide to Autism
Brain Changes in Autism: Study Details

Researchers have suspected that the brains of children with autism ''are just connected differently," Wolff says. Other studies have shown differences, he says. These other studies have focused mainly on older children.

Piven's team suspected that autism unfolds much earlier. They designed the new study to look closely beginning in infancy.

The researchers tracked 92 high-risk infants. All had an older sibling who had autism spectrum disorder. They began at age 6 months.

The researchers used a special magnetic resonance imaging (MRI) to evaluate the infants' brains at 6 months, 1 year, and 2 years. They produced three-dimensional images to show the changes over time in each child's white matter.

They looked at 15 white matter areas.

They did behavioral assessments at 24 months. They looked for symptoms of autism spectrum disorder. At 24 months, 28 children were diagnosed with ASD. The other 64 were not.

"We looked at 15 different connections and 12 of those showed abnormal connections in the kids who developed autism," says researcher Geraldine Dawson, PhD, a professor of psychiatry at the University of North Carolina Chapel Hill and another study co-author.

"These results are preliminary and we are not at a point yet where we can use these imaging techniques to screen for autism," she says.

The study reinforces the idea that autism unfolds over time, rather than developing overnight after some trigger, Piven and Wolff tell WebMD.

The study was funded by the National Institute of Child Health and Development, Autism Speaks, and the Simons Foundation. Dawson is chief science officer for Autism Speaks, an advocacy and research organization. One co-author, Alan C. Evans, PhD, reports a consulting fee from Biospective, an imaging contract research organization. He has an equity position in the firm, as founder.

Brain Changes in Autism: Perspective

The new finding about brain changes in autism is an important clue, says Christine Wu Nordahl, PhD, assistant adjunct professor of psychiatry and behavioral sciences and an autism researcher at the M.I.N.D. Institute, University of California, Davis.

"To try to find out any sorts of brain changes that are happening prior to the diagnosis is really critical for the field," she tells WebMD. She reviewed the findings but was not involved in the research.

One limitation, she says, is the lack of a ''low-risk" group for comparison. All the infants had older siblings with ASDs. That puts them at higher risk than other children. The researchers also note this limitation.

"We're a step closer to understanding the brain changes that may be happening before the clinical diagnosis is made," Nordahl says. Eventually, these earlier clues may lead to earlier intervention. "That's what we are hoping for.”