Research: Autistic children's brains grow larger during first years of development, why is not clear

December 05, 2005

By age 2, children with the often-devastating neurological condition physicians call autism show a generalized enlargement of their brains, a new University of North Carolina at Chapel Hill and Duke University medical schools study concludes.

Exactly why this roughly 5 percent greater brain growth occurs and what it means are not yet clear, scientists said. Indirect evidence suggested that the increased brain growth probably began during the later months of the children's first year of life.

A report on the finding appears in the December issue of the Archives of General Psychiatry. UNC authors are Dr. Heather Cody Hazlett, assistant professor of psychiatry; Dr. Michele Poe, a statistician with the FPG Child Development Institute; Dr. Guido Gerig, professor of computer science; imaging technician Rachel Gimpel Smith; and Drs. John Gilmore and Joseph Piven, professors of psychiatry.

At UNC, Piven, the senior author, directs both its Study to Advance Autism Research and Treatment (STAART) Center and its Neurodevelopmental Disorders Research Center. Duke authors are Drs. James Provenzale and Allison Ross, professor of radiology and associate professor of anesthesiology, respectively.

"Our team conducted brain magnetic resonance imaging scans on 51 autistic and 25 control children at age 2, making it the largest study of two-year-olds with autism," Cody Hazlett said. "Analysis of brain tissue volumes showed significant enlargement, across all regions in both gray and white tissue, in the cerebral cortex of the autistic children.

"While we saw the greatest volume increases in the temporal lobe, an area of the brain involved in language, we concluded that at this age, tissue enlargement is present throughout the cortex."

In the same paper, the team reported on the largest retrospective study of head circumference in autism reported to date, comparing head circumference measurements on 113 autistic children to 190 other youngsters who served as controls. Measurements took place periodically from birth to age 3.

"Our head circumference data suggest that enlarged head size is not present at birth and that the onset of enlarged head size in autistic children begins, on average, at around 12 months," Cody Hazlett said. "These findings, together with our brain volume data, give us reason to believe that a period of brain overgrowth in autism may occur between 12 months and 2 years of age.

"We do not know whether this brain enlargement plays a primary role in autism, or is a downstream effect of another process," she said. "Further studies of very early brain development may help us better understand the timing and nature of this brain overgrowth."

About four times as many male children suffer from autism as females, Cody Hazlett said. The disorder varies in severity, but affected patients often face mental retardation, poorly developed language skills and difficulty developing social relationships.

Grant support for the study, which builds on earlier work, came from the National Institutes of Health's mental health and child and human development institutes (NIMH and HICHD). Assistance also came from the Treatment and Education of Autistic and Related Communication Handicapped Children (TEACCH) centers and the Neurodevelopmental Disorders Research Center Autism Subjects Registry.

Note: Cody Hazlett can be reached at (919) 260-2674 or heather_cody@med.unc.edu.

News Services contact: David Williamson, (919) 962-8596
-end-


University of North Carolina at Chapel Hill

Related Autism Articles from Brightsurf:

Autism-cholesterol link
Study identifies genetic link between cholesterol alterations and autism.

National Autism Indicators Report: the connection between autism and financial hardship
A.J. Drexel Autism Institute released the 2020 National Autism Indicators Report highlighting the financial challenges facing households of children with autism spectrum disorder (ASD), including higher levels of poverty, material hardship and medical expenses.

Autism risk estimated at 3 to 5% for children whose parents have a sibling with autism
Roughly 3 to 5% of children with an aunt or uncle with autism spectrum disorder (ASD) can also be expected to have ASD, compared to about 1.5% of children in the general population, according to a study funded by the National Institutes of Health.

Adulthood with autism
The independence that comes with growing up can be scary for any teenager, but for young adults with autism spectrum disorder and their caregivers, the transition from adolescence to adulthood can seem particularly daunting.

Brain protein mutation from child with autism causes autism-like behavioral change in mice
A de novo gene mutation that encodes a brain protein in a child with autism has been placed into the brains of mice.

Autism and theory of mind
Theory of mind, or the ability to represent other people's minds as distinct from one's own, can be difficult for people with autism.

Potential biomarker for autism
A study of young children with autism spectrum disorder published in JNeurosci reveals altered brain waves compared to typically developing children during a motor control task.

Autism often associated with multiple new mutations
Most autism cases are in families with no previous history of the disorder.

State laws requiring autism coverage by private insurers led to increases in autism care
A new study led by researchers at the Johns Hopkins Bloomberg School of Public Health has found that the enactment of state laws mandating coverage of autism spectrum disorder (ASD) was followed by sizable increases in insurer-covered ASD care and associated spending.

Autism's gender patterns
Having one child with autism is a well-known risk factor for having another one with the same disorder, but whether and how a sibling's gender influences this risk has remained largely unknown.

Read More: Autism News and Autism Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.