The apparent rise in Autism Spectrum Disorder (ASD) in the last few decades has been the subject of much research, some debate, and, unfortunately, few conclusions. There have been discoveries regarding the role of oxytocin and the possible influence of environmental triggers, along with genetic variations that may make ASD more likely in some people than others.

What has been clear for a long time is that boys are particularly susceptible to ASD, as well as ADHD and other kinds of intellectual disability, compared to girls.

The reason for this gender difference has been somewhat of a mystery, but a new study shows that boys may be at greater risk because fewer genetic variations trigger ASD in the male brain than in the female brain.

Compared to boys, girls are better able to withstand more ‘hits’ to the genome when it comes to triggering ASD, making them more resistant to such disorders.

Researchers studied 16,000 families with neurodevelopmental disorders and 800 families with ASD and looked at the genetic differences between boys and girls. They focused on two different types of genetic mutation known to be related to the disorder.

Girls with ASD had many more of both types of genetic mutation than did boys with ASD. This suggests that girls may be better able to withstand "hits" to the genome when it comes to triggering ASD, compared to boys, making them more resistant to such disorders.

When it comes to the gender differences in brain development, “females seem to have a clear advantage,” study author Sébastien Jacquemont said in a statement. “Overall, females function a lot better than males with a similar mutation affecting brain development.”

The results add weight to the idea that the female brain is more resilient than the male brain when it comes to problems affecting the growth and development of the brain and central nervous system and disorders affecting emotions, learning ability and memory.

The next step will be to determine exactly why, in the face of similar genetic variations, the female brain is able to protect itself against ASD. Now that we have gained some insight about the kinds of genetic changes that are necessary to trigger the disorder, the researchers believe we will soon have gender-based diagnostic tests. And, perhaps in the future, gender-based treatments will be available.

The study was carried out by researchers at the University Hospital of Lausanne in Switzerland and the University of Washington School of Medicine. It is published in the American Journal of Human Genetics.