Understanding Sex Differences in Autism

Our Leading Theories on Autism Gender Differences
1. Evidence is growing that females have a degree of protection against autism – versus just being less diagnosed. As recently reported on this website, researchers at Harvard Medical School found that, overall, it takes more autism risk genes to tip girls’ brain development onto the autism spectrum than it does for boys. Though the study looked only at inherited gene mutations, it may be that boys are also more vulnerable to nongenetic, or “environmental,” risk factors. (Read more about environmental factors and autism here.)

2. The “female protect effect” may stem, in part, from our sex chromosomes. As you may remember from high-school biology, humans have 23 matched pairs of chromosomes. Sex is determined by the 23rd pair: Girls have two Xs. Boys have an X and Y. The extra protection for girls might come from those two matched Xs. They may provide a level of gene duplication that protects against a gene mutation on either X. By contrast, a mutation on a boy’s X or Y chromosome may prove more harmful because he lacks that matched backup copy.

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