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Study Finds Overgrowth in Key Brain Structure in Babies Who Develop Autism

May 10, 2022

A study conducted by the Infant Brain Imaging Study (IBIS) network has found that a key structure in the brain, known as the amygdala, increases in size in babies between the ages of 6 and 12 months who later develop autism spectrum disorder (ASD). What is interesting about this study is that it may potentially identify the earliest signs of autism in an individual.

Study Finds Overgrowth in Key Brain Structure in Babies Who Develop Autism 

The amygdala and autism

The amygdala is an important structure in the brain that allows us to interpret sensory input. This includes but is not limited to, recognizing faces, understanding facial expressions, and sensing when something is to be feared. The amygdala has long been associated with social difficulties faced by autistic individuals. This study allows us to understand a bit more about this key brain structure and the impact it has on people with autism.

The growth of the amygdala in autistic patients is not new, and yet in the past, it has always been associated with school-age children. Exactly when the growth took place had remained a mystery, until now.

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For the first time, researchers at the IBIS network were able to use magnetic resonance imaging (MRI) to provide evidence of key brain growth of the amygdala in babies during their first year.  A child’s overgrowth appears to begin between 6 and 12 months of age before the recognizable characteristics of autism emerge; this could potentially signify the earliest identification of autism in individuals.

According to the study: “Infants who developed ASD had typically sized amygdala volumes at six months but exhibited significantly faster amygdala growth between 6 and 24 months, such that by 12 months the ASD group had significantly larger amygdala volume compared with all other groups. The amygdala growth rate between 6 and 12 months was significantly associated with greater social deficits at 24 months when the infants were diagnosed with ASD.”

Is the overgrowth present in other neurodevelopmental disorders?

The study compared the overgrowth of the amygdala in infants who were likely to develop autism and were later diagnosed, infants who were likely to develop ASD but were not diagnosed, infants with other neurodevelopmental disorders, such as fragile x syndrome, and control infants. 

Fragile x syndrome is a genetic condition that causes developmental problems such as learning disabilities and cognitive impairment.

The study compared the overgrowth of the amygdala between infants who were likely to develop ASD and those who were likely to develop fragile x syndrome. The result indicated that brain growth between the two groups was markedly different.

The study states: “Fragile X syndrome-related changes were present from six months of age, whereas ASD-related changes unfolded over the first two years of life, starting with no detectable group differences at six months.”

In a report from the University of Washington News, Dr. Stephen Dager, Professor of Radiology in the UW School of Medicine and an Adjunct Professor of Bioengineering, said: “We are getting closer to understanding why autism occurs by learning more about brain growth alterations early during development, in this case how amygdala growth may be influenced by early sensory processing difficulties and, conversely, how amygdala growth alterations may influence a baby’s interaction with their environment.”

To sum up

It is interesting to note that what we know about autism is forever developing. This new research tells us that the overgrowth of the amygdala in infants between the ages of 6 and 12 months could indicate the presence of autism, allowing us to seek early intervention sooner rather than later.


Eckhart, K.(2022, March 29) Scientists identify overgrowth of key brain structure in babies who later develop autism. UW News


Shen M.D, Swanson M.R, Wolff J.J, Ellison J.T, Girault J.B, Kim S.H, Smith R.J, Graves M.M, Weisenfelf L.A, Flake L, MacIntyre L, Gross L.J, Burrows C, Fonov V.S, Collins L, Evans C.A, Gerig G, Mckinstry R, Pandey J, St.John T, Zwaighenbaum Z, Estes A.M, Dager S.R, Schultz R.T, Styner M.A, Botteron K.N, Hazlett H.C, Piven J.(2022, March 25) Subcortical Brain Development in Autism and Fragile X Syndrome: Evidence for Dynamic, Age- and Disorder-Specific Trajectories in Infancy. The American Journal of Psychiatry


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