Men and boys are more likely to be diagnosed with ASD than women and girls.[1] There are a variety of explanations for this discrepancy — some biological; some methodological.
Genetics and prenatal androgen exposure have both been implicated in differing rates of autism between sexes. It has been hypothesized that the paternal X chromosome may play a role in protecting women and girls from developing ASD [2]. During fetal development, one X chromosome in female babies’ cells expresses its 1,100 genes while the other is inactivated. The inactivation of this X chromosome makes it less likely for mutated genes to be expressed in developing female cells.[3][4]
Some researchers propose that women and girls who were exposed to excess androgens in utero are at greater risk of developing autistic traits,[5][6] but this is controversial.[7]
It’s also possible that the current assessment tools for ASD are less effective at capturing features of ASD that are unique to women and girls (a phenomenon known as “diagnostic bias”).[8] For example, women and girls with ASD are more likely to camouflage or mask[9] their behaviors, meaning that they may adopt a socially acceptable persona by copying facial expressions and purposefully making eye contact. Since social behavior, eye contact, and facial expressions all factor in to an ASD diagnosis, someone with ASD who masks their behaviors may not be diagnosed as having the condition.