Autism is Inherited From Mom

When it comes to developmental disorders of the brain, men and women are not created equal.

Decades of research have shown that males are at far greater risk for neurodevelopmental disorders such as autism spectrum disorder (ASD) than females. Boys, on average, are five times more likely to have autism than girls . What causes this disparity has largely remained unknown.

Now scientists have uncovered compelling genetic evidence to explain why the biological scales aren’t balanced.

According to a team of geneticists in the U.S. and Switzerland, it all boils down to what’s called the “female protective model.” This suggests that girls have a higher tolerance for harmful genetic mutations and therefore require a larger number of them than boys to reach the diagnostic threshold of a developmental disorder. With identical genetic mutations, then, a boy could show symptoms of ASD while a girl could show none.

But because the female mutation threshold is higher, when girls are diagnosed with ASD, they tend to fall on the more severe end of the spectrum.

Researchers believe the same dynamic could explain why more boys are diagnosed with ADHD, intellectual disabilities and schizophrenia. The findings were published Thursday in the American Journal of Human Genetics.

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