We’re excited to post the following blog on a topic we don’t hear much about – girls and autism. Because they are in the minority when it comes to autism diagnosis, girls have not received attention as a unique subset of people with autism. That seems to be changing! Here’s what two of our colleagues at the University of Washington Autism Center, Sara Webb, PhD, and Katy Ankenman, MSW, shared with us about their study on girls and autism.

It is common knowledge that autism spectrum disorder (ASD) is diagnosed more often in boys than girls. Current prevalence rates tell us that boys are at higher risk of ASD as the ratio of boys to girls with ASD is about 4.5:1. The recent Centers for Disease Control (CDC) estimate found a ratio of 1 in 42 boys and 1 in 189 girls diagnosed with ASD. But why? Researchers have been wrestling with this question for years. Two new studies have yielded some promising explanations for the apparent gender divide in autism and have also raised new questions.

A recent paper from scientists at the University of Washington provided evidence that girls seem to be more protected from ASD than boys at a genetic level. They discovered that girls with ASD in their sample tended to have more and larger genetic events (sometimes called mutations) in their DNA than boys. One way to interpret this finding is that it may be harder for a girl to develop autism than a boy because it takes more of a genetic “hit” for girls to develop autism.

Another paper identified behavioral and cognitive differences in a large sample of boys and girls with ASD. They found that girls had greater social communication problems, lower cognitive ability (IQ) and adaptive behaviors, and increased problem behaviors, such as irritability, compared to boys. Interestingly, they also found lower levels of restricted interests in girls. As other studies have shown, there were fewer girls with ASD with cognitive abilities in the average range or above in this sample.

Among children with ASD and intellectual disability, the gap between the number of boys to girls is more narrow (roughly 2:1). As intellectual and adaptive ability increases, however, estimates rise to 7 (or more) boys diagnosed for every 1 girl. One explanation for this difference is that girls with ASD with with higher IQ and better adaptive ability might present differently than boys and thus be missed using today’s diagnostic standards, especially in the repetitive behavior domain.

Whatever accounts for the difference between the number of boys and girls diagnosed with ASD, it’s well-known that girls with ASD and without intellectual disability are often not diagnosed until much later than their male counterparts. This can be detrimental to many girls who could have benefited from earlier intervention, treatment and support.

Unfortunately, research looking at neurological, behavioral and genetic differences between boys and girls with ASD, until recently, has been sparse. Many studies investigating ASD do not have a large enough group of girls participating to reach firm conclusions. Seattle Children’s is hoping to change this. The Seattle Children’s Research Institute, in conjunction with 3 collaborating sites across the nation, is currently conducting a large-scale NIH funded study investigating the differences between 125 girls and 125 boys with ASD. Our hope is that the research we are conducting here will help improve our understanding of symptom and genetic patterns in girls and boys, benefiting their lives and the lives of their families.

Help the Seattle Children’s Autism Center and Burnett Adult Life Center grow! When you make a gift to either this month, your donation will be matched dollar for dollar thanks to The Bradley Family Foundation. Donate at https://giveto.seattlechildrens.org/AutismMatch to qualify for the match.