When we talk about autism, we're usually talking about boys with autism.
This is where the research has focused, largely due to the fact that they outnumber girls with autism four to one. That focus may have kept us from identifying important differences between the sexes when it comes to autism.
So, what about girls?
A large new study finds significant deviations in brain structure and behavior between boys and girls with autism -- a finding that could help clinicians to better identify and treat the disorder in both sexes.
"Girls with autism display autism symptoms differently, and this may lead them to be underdiagnosed or may make it harder for them to get the most appropriate treatment," Dr. Vinod Menon, a professor of psychiatry and behavioral sciences at Stanford School of Medicine and one of the study's authors, told The Huffington Post in an email.
Understanding the differences between the sexes is "really quite crucial," Menon said in a written statement.
Specifically, girls tend to show less repetitive behaviors than boys do.
Repetitive and restricted behaviors -- including repeated body movements such as rocking or hand-flapping, a narrow scope of interests, and a need for rigid routines -- are one of the main facets of autism, along with social and communication deficits.
For the study, which was published Thursday in the journal Molecular Autism, the researchers analyzed brain scans and diagnostic data on 742 U.S. children (614 boys and 128 girls) between the ages of 7 and 13, all with high-functioning autism.
While the boys and girls had similar IQ scores, as well as comparable social behaviors and communication skills, the boys showed significantly more repetitive and restricted behaviors than the girls did.
These behavioral differences seem to be rooted in structural differences in the brain. Analysis of the brain scans revealed that autistic boys had different brain patterns in regions associated with motor function and planning of motor activities.
So should girls with autism be diagnosed and treated differently from boys? Possibly -- but more research needs to be done first, says Dr. Paul Wang, head of medical research for the advocacy group Autism Speaks.
"Everybody who is involved -- parents, pediatricians, school psychologists -- needs to be tuned in to make sure that they're not missing autism in girls," Wang, who was not involved in the study, told HuffPost. "We have to make sure we're not missing more subtle social and communication skills that could be autism."