Researchers at the University of North Carolina conducted a study in an attempt to understand the brain enlargement observed in 2-year-old children with autism.
Using magnetic resonance imaging (MRI) to observe brain growth in young children – 59 with autism spectrum disorder (ASD) and 38 without the ASD diagnosis – they found children with autism not only tend to have larger brains, but that this increased rate of brain growth occurs before the age of 2, according to a report from the Archives of General Psychiatry.
They followed up with the children two years later – 38 with ASD and 21 in the control group – only to discover that, although children with ASD had an enlarged cerebral cortex and increased temporal lobe white matter, there was no difference in the rate of brain growth between the two groups over the two-year time span.
Researchers concluded that the overgrowth of the brain must occur before the age of 2. Scientists have known of the link between brain development and autism, but have not been able to define the cause or exact time frame.
Based on these findings, the authors suggest that "brain overgrowth had its onset in the latter part of the first year of life," and noted that future studies would focus “on this narrow window of brain development."
Study authors also state that identifying the timeframe when brain changes occur can help isolate "brain markers that may increase prediction of ASD risk."