The theory that genes play a role in the development of autism is not new, and a recent study suggests that girls may be protected against autistic behavioral impairments because of their unique genetic makeup. 

Researchers from the Harvard School of Public Health wanted to know why boys are five times more likely to develop autism, and they found that girls require “a greater number of familial risk factors to show the same degree of autistic behavioral impairment.”

The Basics of Autism

Autism is one of what are known as pervasive developmental disorders. Symptoms of autism include delays in language, social, and cognitive development, which may appear when a child is as young as three years old. Those with severe symptoms may have difficulty in school and in social situations, but proper intervention can help address these complications.

According to the non-profit awareness group Autism Speaks, autism affects one in 88 children and one in 54 boys. This disparity made researchers wonder whether girls are somehow protected from autism's devastating effects.

Twins and Autism

Elise Robinson, a post-doctoral fellow at Harvard, and her colleagues looked for behavior patterns in a total of 9,882 pairs of fraternal (non-identical) twins participating in the Twin’s Early Development Study in the U.K. and the Child and Adolescent Twin Study in Sweden.

They found that in both the U.K. and Swedish populations, boys whose sisters displayed autistic symptoms showed significantly greater impairment than girls whose brothers displayed autistic symptoms.

Because fraternal twins rarely share the same genetic profile, researchers concluded that girls are born with some type of protection against autistic impairment that boys don’t share.

What’s Next?

While the researchers didn’t delve into details about this “protection,” their research does help to explain why girls have a much lower incidence of autism than boys.

Further research, especially at the genetic level, will help us better understand the causes of the condition, as well as guide the future of autism screening and treatment.

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