Researchers at UC Davis have made a significant discovery about how autism affects brain development differently in boys and girls.
Their findings, which were shared in the journal Molecular Psychiatry, highlight the unique patterns of brain growth in autistic children between the ages of 2 and 13.
Historically, boys have been diagnosed with autism far more frequently than girls, with a ratio of nearly four to one. Christine Wu Nordahl, a leading researcher in this study, suggests that this difference is partly due to girls being underdiagnosed.
However, the recent findings indicate that the disparity in diagnosis is not just a matter of recognition; there are genuine biological differences at play.
The study primarily focused on the cortex, the brain’s outer layer crucial for thinking, learning, remembering, and emotional processing.
This layer is composed of several layers filled with neurons, the cells responsible for transmitting information throughout the brain.
In early childhood, particularly around age 2, the cortex thickens rapidly as new neurons form. This is followed by a period of thinning, which continues into adolescence.
Prior research has shown that this thinning process occurs differently in autistic children compared to those who are not autistic.
The UC Davis study took this a step further by examining whether the patterns differed between autistic boys and girls.
The research involved detailed brain scans of 290 autistic children (202 males and 88 females) and 139 non-autistic children (79 males and 60 females).
These children were part of the Autism Phenome Project (APP) at the MIND Institute, one of the largest studies of its kind.
The researchers also launched a sub-study called the Girls with Autism Imaging of Neurodevelopment (GAIN) to ensure that enough data on females were included, given their historical underrepresentation in autism research.
The results were eye-opening. At age 3, autistic girls exhibited a significantly thicker cortex than their non-autistic counterparts—around 9% thicker across various parts of the brain. This difference was not as pronounced in autistic boys compared to non-autistic boys.
Furthermore, the rate at which the cortex thinned during childhood was faster in autistic girls than in boys. This rapid thinning in girls led to a situation where, by middle childhood, the differences between autistic boys and girls were much less obvious.
Derek Andrews, the lead author of the study, expressed surprise at these findings. The differences were most notable at younger ages—a critical period for brain development.
Andrews pointed out that the timing of these developmental changes could lead to significant differences that eventually converge as children grow older.
The study underscores the importance of including both sexes in autism research. “If we had only looked at boys at age 3, we might have missed these differences,” Nordahl explained.
This approach allows researchers to capture a complete picture of developmental changes in autistic children.
Nordahl’s commitment to increasing the representation of females in autism research led to the launch of the GAIN study in 2014.
Despite females making up about 20% of the autistic population, they are often overlooked in studies. Andrews hopes that other researchers will follow their lead in ensuring that autistic girls are adequately represented.
The study’s collaborative efforts included contributions from Kersten Diers and Martin Reuter of the German Center for Neurodegenerative Diseases, and several researchers from Massachusetts General Hospital and UC Davis.
Their collective work shines a light on the nuanced ways autism manifests differently across genders, highlighting the need for diverse and comprehensive research approaches in understanding this complex condition.
If you care about autism, please read studies about a new cause of autism, and cats may help decrease anxiety for kids with autism.
For more information about health, please see recent studies about vitamin D that may hold the clue to more autism, and results showing strange eating habits may signal autism.
The research findings can be found in Molecular Psychiatry.
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