Autism spectrum disorder is diagnosed much more frequently in boys than girls, at a ratio of 4 to 1. Despite recent efforts, little research has been done on girls - there are fewer of them, so fewer are represented in autism research. An estimated 1 in 42 boys has autism; in girls the statistic is 1 in 189.
The U.S. Centers for Disease Control and Prevention currently estimates the overall incidence of autism at 1 in 68 children born today.
In a brain study, the researchers found differences in the corpus callosum, the region of the brain that connects the left and right hemispheres.
That study is published online today in the journal Molecular Autism, as part of a special issue devoted to gender differences. It adds to the growing body of evidence that suggests that in autism, there are underlying biological differences between boys and girls.
The magnetic resonance imaging (MRI) study of brain structure was conducted in a large sample of 3- to 5-year-old children, 112 boys and 27 girls — a large number for girls with autism — and 53 boys and 29 girls who were developing typically and served as control subjects.
For the preliminary research presented at IMFAR, Nordahl explored behavioral differences in boys and girls with autism. Research in the area previously has been inconsistent.
"Most behavioral studies of gender differences directly compare males and females with autism. Our approach was to evaluate social impairments in a large group of children that included girls and boys with both autism and typical development," Nordahl said. "We were interested not only in directly comparing boys and girls with autism, but also in assessing how boys and girls with autism compare in relation to their typically developing peers."
"We found that the behavioral differences between girls with autism and typically developing girls are much larger than differences between boys with autism and typically developing boys," she said. "In other words, girls with autism deviate further from typically developing girls than boys with autism relative to typically developing males, suggesting that girls with autism have more severe social impairments than boys."
Nordahl said that much more works needs to be done to understand the sex differences between male and female children with autism, and particularly, increasing the numbers of female children who participate in autism research.
Category(s):Autism spectrum disorders, Child Development
Source material from UC Davis
