Girls with autism display less repetitive and restricted behavior than boys do, according to a study by researchers at the Stanford University School of Medicine.

The study also found that brain differences between boys and girls with autism help explain this discrepancy.

The study, published online Sept. 3 in Molecular Autism, gives the best evidence to date that boys and girls exhibit the developmental disorder differently.

“We wanted to know which specific clinical manifestations of autism show significant gender differences, and whether patterns in the brain’s gray matter could explain behavioral differences,” said the study’s senior author, Vinod Menon, PhD, professor of psychiatry and behavioral sciences. Knowledge of the difference could help clinicians better recognize and treat autism in both sexes, he added. “Understanding this is really quite crucial clinically.”

“We found strong evidence for gender differences in autism,” said postdoctoral scholar Kaustubh Supekar, PhD, the study’s lead author. The researchers used two large, public databases to examine nearly 800 children with high-functioning forms of autism in the United States, he said.

Repetitive and restricted behavior is perhaps the most widely recognized of the three core features of autism. It can show up as a child’s preoccupation with a narrow interest, inflexibility about routines or repetitive motions such as hand-flapping. The other core features of autism are social and communication deficits.

More boys with high-functioning autism

Among children diagnosed with the high-functioning form of autism, boys outnumber girls by four to one. Scientists were interested in comparing the expression of core features of the disorder between sexes because they have long suspected girls with autism may display symptoms differently, causing them to be underdiagnosed or making it harder for them to get the most appropriate treatment.