Researchers may have uncovered why autism is more common in boys than girls, USA Today reported.

Researchers from the University Of Washington School Of Medicine and the University Hospital of Lausanne in Switzerland found that the reasons males are at a greater risk for neurodevelopment disorders such as, autism spectrum disorder, may be because females require more extreme genetic mutations than do males to push them over the diagnostic threshold for neurodevelopmental disorders.

About 1.8 per cent of boys have autism compared to just 0.2 per cent of girls, The Daily Mail reported.

"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," study author Sébastien Jacquemont of the University Hospital of Lausanne said in a statement. "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 analyzed DNA samples and sequencing data sets of one cohort consisting of nearly 16,000 individuals with neurodevelopmental disorders and another cohort consisting of about 800 families affected by autism spectrum disorder. The researchers analyzed both copy-number variants (CNVs) - individual variations in the number of copies of a particular gene - and single-nucleotide variants (SNVs) - DNA sequence variations affecting a single nucleotide.

They found that females diagnosed with a neurodevelopmental disorder or autism spectrum disorder had a greater number of harmful CNVs than did males diagnosed with the same disorder. They also found that females diagnosed with autism spectrum disorder had a greater number of harmful SNVs than did males with autism spectrum disorder.

The findings suggest that the female brain requires more extreme genetic alterations than does the male brain to produce symptoms of autism spectrum disorder or neurodevelopmental disorders. The results also take the focus off the X chromosome for the genetic basis of the gender bias, suggesting that the burden difference is genome wide.

"Overall, females function a lot better than males with a similar mutation affecting brain development," Jacquemont said. "Our findings may lead to the development of more sensitive, gender-specific approaches for the diagnostic screening of neurodevelopmental disorders."