Why Are There So Many More Autistic Males Than Females?
One part of the answer is straightforward: Some instances of autism are inherently more common among males because males have only one X chromosome (Bartholomay et al., 2019). For example, males are more susceptible to severe symptoms of fragile X syndrome, which is caused by changes in a gene on the x chromosome. Fragile X often co-occurs with autism. Females have two X chromosomes, which means one chromosome can sometimes compensate for the other, making them less susceptible to fragile X and, in turn, autism. There are other similar examples, such as Klinefelter syndrome. Because of this, there might always be a gender gap in autism.
For 2008, the U.S. Centers for Disease Control and Prevention reported a ratio of 1 to 4.7 (Baio, 2012). But the most recent data from the agency show a female-to-male ratio of 1 to 3.8 for autism diagnoses among 8-year-old children (Maenner et al., 2023). That is a huge change in a short amount of time.
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Why Are There So Many More Autistic Males Than Females?
One 2020 study used genetic analysis to address this question (Zhang et al., 2020). The researchers looked at 174 different genes and compared how they are expressed in males with ASD, females with ASD, and unaffected control participants.
Among the autistic subjects, females were likelier than males to express the genes the researchers studied. The authors cited this as evidence for a “female protective effect” such that “a higher threshold of genetic liability is required for [autistic] females as compared with [autistic] males.”
I am not here to argue with their conclusions or to criticize their methods, as I am not a geneticist. Instead, I would like to explore a question the authors raised further.
They wrote that “a higher genetic load was required in females to reach the threshold for a diagnosis” of ASD.
The italics above are mine. Zhang et al. chose their words with appropriate care. To clarify, I read them as an acknowledgment that having autism and being diagnosed with it are not always the same thing and that their research can be linked only to diagnosis. Elsewhere in the article, they addressed issues similar to the ones I’ve raised above, pointing to research that suggests bias in the way we diagnose autism and specifically in the way that we diagnose females. These issues “might influence the sample and some conclusions,” the authors wrote. That brings me to my last question.
Source :
https://autismspectrumnews.org/genetics-diagnosis-and-the-male-female-gender-gap-in-autism/
