Research Sheds Light on Why Autism Is More Prevalent in Boys

A new study is helping unravel an enduring mystery surrounding autism: Why boys are much more likely to be affected by the disorder than girls. An international team led by Dr. John Vincent, of the Centre for Addiction and Mental Health in Toronto, examined specific genes in almost 3,000 people with an autism spectrum disorder (ASD) and 246 others with intellectual disability. They then compared that data to genes from more than 10,000 control individuals. Reporting in the Sept. 15 issue of Science Translational Medicine, the team found that mutations in the PTCHD1 gene are linked to inherited forms of autism and intellectual disability in about 1 percent of affected people in the study. It was not found in any of the controls, however. "Our data indicate that mutations at the PTCHD1 locus are strongly associated with ASD," the researchers concluded. They also noted that this gene is typically located on the single X-chromosome in males.

The study "provides further clues as to why ASD affects four times more males than females," said Andy Shih, vice president for scientific affairs at Autism Speaks. "PTCHD1 is part of a neurobiological pathway that determines the development of human embryos. It is one of several genes recently implicated in both ASD and intellectual disabilities." The finding adds a little more clarity to the murky origins of autism, Shih said. While each new genetic discovery "may only account for a small fraction of the cases, collectively they are starting to account for a greater percentage of individuals in the autism community, as well as providing insights into possible common pathogenic mechanisms," he said. "Identification of a male-linked genetic mutation begins to address the previously unknown basis for often reported skewed male-to-female ratio in autism."