Boys are nearly four times more likely to be diagnosed with autism than girls–a statistic that has caused much controversy could possibly have more scientific backing than once presumed. Although undiagnosed girls with autism are more likely to mask their autism and go through life presenting as neurotypical, some instances of autism are inherently more common among males due to genetic factors. Specifically, males only have one X chromosome, so mutations on the X chromosome–such as those seen in Fragile X syndrome–present more severely in males as opposed to females, who have another X chromosome to mask such mutations. This means that girls in general are less susceptible to fragile X syndrome and some forms of autism that may contribute to the demonstrated sex difference in diagnosis. An important question arises: to what extent does biological vulnerability contribute to differences in how boys and girls with autism experience and process social information, such as recognizing faces?
In the research paper “Neural correlates of face processing among preschoolers with fragile X syndrome, autism spectrum disorder, autism siblings, and typical development”, Dr. Maggie W. Guy and colleagues examine patterns of brain responses to faces, houses, and other images and experiences in preschoolers. The study examined how preschoolers with autism, fragile X syndrome, autistic siblings, and typically developing children process faces and houses, using EEG/ERP signals with P1 and N170 components. Children with FXS showed larger P1 and N170 amplitudes, suggesting hyperresponsivity to visual stimuli. Children with ASD and ASIBs had reduced N170 amplitudes, especially to faces, suggesting weaker social processing.
These findings and studies directly connect: Fragile X syndrome, caused by an X chromosome mutation, leads to more severe effects in males because they lack a second X to cover up the mutation. Since FXS is often associated with autism, the FXS boys in Dr. Guy’s study shows hypersensitivity to visual stimuli and weaker social processing of faces, supporting the idea that biological sex differences in the genetic and neural components of autism may lead to higher rates of autism diagnosis in boys. Additionally, brain activity differences in Dr. Guy’s study were found in preschool-aged children, demonstrating that boys’ brains respond differently to social information very early, potentially leading to earlier detection, while girls might mask symptoms or have less prominent brain signals, leading to underdiagnosis.
One direction that future research can take is to look more closely at how sex differences in brain function develop over time across the autism spectrum for both boys and girls. Longitudinal studies following both boys and girls from infancy through childhood could reveal when these differences first emerge. Studies can also investigate whether different types of brain measures such as EEG or fMRI might detect different types of brain activity that are differently prevalent in boys and girls. Understanding both genetic factors (like X-linked vulnerabilities) and neural processing differences is essential for creating better diagnostic tools that are sensitive to girls’ and boys’ different presentations of autism.
References:
Samelson, Doreen. “Genetics, Diagnosis, and the Male-Female Gender Gap in Autism.” Autism Spectrum News, 24 Jan. 2024, autismspectrumnews.org/genetics-diagnosis-and-the-male-female-gender-gap-in-autism/.
Richards, J. E., Guy, M. W., Hogan, A. L., & Roberts, J. E. (2024). Neural correlates of face processing among preschoolers with fragile X syndrome, autism spectrum disorder, autism siblings, and typical development. Autism Research, 17(1), 89–108. https://doi.org/10.1002/aur.3045