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Girls' brains are more 'resilient' than boys' to disorders such as autism and ADHD

Extra X chromosone could explain why neurodevelopmental disorders are more frequent in males than females

New research suggests that girls’ brains are more “resilient” than boys to neurodevelopmental conditions such as autism.

The cohort study found evidence supporting the “female protective model”, a theory that suggests that females require more extreme genetic mutations than males before they develop certain sorts of disorders.

This would account for the gender difference for conditions such as autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD), both of which are diagnosed more frequently in males than females.

An alternative theory accounting for this difference suggests that social bias is responsible, although this research – which looked at genetic data from more than 15,000 individuals – found that that females diagnosed with ASD had a greater number of harmful genetic mutations than males.

"The data suggests - and it would require additional experiments to really prove this - but it looks like there is a resilience in brain development that is much higher in females than in males," lead author Sebastien Jacquemont of the University Hospital of Lausanne, Switzerland, told the BBC.

"You can 'break' neurodevelopment in males much easier than you can in females."

Jacquemont said he hoped that that the research might lead to the development of "more sensitive, gender-specific approaches for the diagnostic screening of neurodevelopmental disorders."

One possible explanation of the imbalance is that females’ extra X chromosome helps them compensate for any extreme genetic damage.

Evan Eichler, a co-author of the study from the University of Washington, said that the results of the study could be interpreted in two ways: either girls are more protected from bad mutations or boys are more susceptible.

"It takes more insult in the genome of a girl to push them over a threshold to develop autism or to develop developmental delay compared to a boy,” said Eichler.