Autistic Behavior Onset Appears to Coincide With Brain Overgrowth at 12 Months

Marlene Busko

May 08, 2008

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Interview with Dr. Piven

May 8, 2008 (Washington, DC) — Changes in behavior and brain circumference appear around 12 months of age in infants later diagnosed with autism, converging research suggests.

Findings from different lines of study suggest that autistic behavior may have its onset in the latter part of the first year of life, at the time that brain overgrowth (enlarged brain volume) seems to occur in autism, said Joseph Piven, MD, from the University of North Carolina, in Chapel Hill, at a press conference about psychiatric risk and the developing brain given at the American Psychiatric Association 61st Annual Meeting.

Three types of investigations — magnetic resonance imaging (MRI) studies of the developing brain, longitudinal studies of head circumference, and early behavioral studies of infants who have siblings with autism — all have found indications that autism onset seems to occur in the early postnatal period, around 12 months of age.

"This convergence [of different research findings] on the postnatal period really points us in a very important direction — to focus our research on that time when these major brain changes may be responsible for the initiation of this disorder, and this has potential implications for understanding the pathogenesis and potential treatment of autism," said Dr. Piven.

Children who are later diagnosed with autism appear to have distinguishing behavioral characteristics at 12 months of age — much earlier than most people would have predicted a few years ago — and this appears to coincide with the onset of brain enlargement, Dr. Piven told Medscape Psychiatry,

Three Research Approaches

Dr. Piven and colleagues performed MRI scans on 2-year-olds — 25 control toddlers and 51 toddlers with autism — and found that the toddlers with autism had generalized enlargement of gray- and white-matter cerebral volumes, but not cerebellar volumes (Arch Gen Psychiatry. 2005;62:1366-76).

In that same study, they examined retrospective, longitudinal head-circumference data from birth to age 3 years in 113 children with autism and 189 local control children and found that in the children with autism, head circumference appeared normal at birth, but the rate of growth began to increase significantly more than in the control children at around 12 months of age.

In a third type of research, Lonnie Zwaigenbaum, MD, and colleagues at McMaster University, in Hamilton, Ontario, reported that infants with autistic siblings who went on to develop autistic spectrum disorders themselves already had defining behavioral features of autism at 12 months of age (Int J Dev Neurosci. 2005;23:143-52).

Teasing Out the Brain-Behavior Relationship

"Siblings of autistic individuals are at a higher risk of developing autism, so it allows you to efficiently study very young children before they develop clear symptoms of autism," said Dr. Piven. Several of these studies suggest that at 6 months of age, the children who went on to develop autism were functioning fairly normally (in their social behavior, for example), but some time after 6 months of age and before 12 to 14 months of age, they developed autistic symptoms, he noted.

Dr. Piven's group is currently involved in a large, 4-site study in the United States that aims to examine over 500 six- and 12-month-old infants at risk of autism and to follow them from 6 through 24 months of age. The researchers will look at brain structure, brain development, and infant behavior to determine the relationship between brain overgrowth and the onset of autism, with findings expected within 5 to 6 years.

"We do see some very focused abnormalities in the brain that seem to be related to specific behavioral and neuropsychological features . . . [but] it's early days in terms of teasing out the brain-behavior relationship in autism," he said.

Dr. Piven indicated he has no significant financial disclosures.

American Psychiatric Association 161st Annual Meeting: Symposium 34. May 3-8, 2008.


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