A new study suggests that a greater number of harmful genetic variants must be present in order for girls to show signs of autism and other neurodevelopmental disorders. (Shutterstock)

New research adds to the theory that girls are more naturally protected than boys from developing autism and other developmental disorders.

While a small number of genetic mutations seem to be enough to manifest symptoms in boys, a new study published Thursday in the American Journal of Human Genetics suggests that far more extreme genetic anomalies must be present in girls to warrant a diagnosis.

The finding could help explain why autism is nearly five times more common in boys.

“This is the first study that convincingly demonstrates a difference at the molecular level between boys and girls referred to the clinic for a developmental disability,” said Sébastien Jacquemont of the University Hospital of Lausanne in Switzerland, the study’s lead author. “The study suggests that there is a different level of robustness in brain development, and females seem to have a clear advantage.”

For the study, researchers looked at DNA samples from more than 16,000 people with autism and other neurodevelopmental disorders. They found that girls with the conditions had a greater number of harmful variations in their genes than did boys with the same diagnosis.

“Overall, females function a lot better than males with a similar mutation affecting brain development,” Jacquemont said.

Researchers said the findings could help bring about more gender-specific diagnosis and screening methods.

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