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Families Help Shine a Light on Girls with Autism

Marina Sarris
September 13, 2016

photo of girl reading book, illustrating blog about researching girls with autismAmong their many contributions to autism research, the families in the Simons Simplex project have given us insight into the lives of girls on the spectrum.

Girls are greatly outnumbered by boys with autism. As a result, researchers essentially ignored them for years. They often would remove girls from autism studies because their low numbers would unfairly skew the results.1

But autism projects such as the Simons Simplex Collection (SSC) and others helped change that. The SSC project gave researchers a large amount of information about a large number of girls with autism – 352 to be exact. The project also included 2,291 boys. Scientists could tap into their genetic and developmental information for studies.

Two recent studies have relied in all or part on SSC data to examine several important questions about girls with autism. Those questions include: Why are girls outnumbered? Is autism different in boys and girls?

One study compared girls in the SSC to girls in three other autism research projects, to see if they had milder or more severe symptoms than the boys.2 But no clear picture emerged. Girls showed milder symptoms in two of the four projects, and greater symptoms in the other two, according to that 2015 study.

In an article in Autism in 2016, researchers Thomas W. Frazier, PhD, and Antonio Y. Hardan, MD, took aim at the tools used to measure (and diagnose) autism.3 Do these tools work equally well for both sexes? This is important because if these tools don't capture female autism accurately – as some have speculated – then some girls may go undiagnosed. That's a special concern for girls on the mild end of the spectrum. According to research by the Interactive Autism Network and others, those girls are diagnosed later than boys. Some girls may not be diagnosed at all.

Using SSC data, Drs. Frazier and Hardan conducted statistical analyses of boys' and girls' scores on various questions measuring autism symptoms.3 Girls had similar levels of symptoms to boys, except in one category: restricted interests. A primary symptom of autism, a restricted interest is an intense focus on an object or topic, such as watching a fan spin, opening and closing doors, or memorizing facts about animals. Girls have lower levels of restricted interests, but that's not the fault of autism diagnostic tests, the researchers concluded. It is likely due to a real difference between the sexes.

In an email, Dr. Frazier explained that boys and girls with autism are not that different, otherwise. "The only difference that seems to be on the table, at the behavioral symptom level, is less restriction of interests, and this may be due to how we capture this symptom. But, if we assume this is an important difference (it might be – at least for identification of high functioning females), I would say it is likely [related to] both neurobiology and early learning." Girls may be less prone to becoming fixated on a single topic or thing, he explained. It's also possible that young girls with mild autism are socialized or taught to "be more flexible and more attentive to other people's interests," he said. "We need to figure this out!"

Thanks to families in the SSC, we are closer to doing just that.

Additional Resources

  1. Bazelon, E. (2007, August 5, 2007). What autistic girls are made of. The New York Times Retrieved from
  2. Howe, Y. J., O'Rourke, J. A., Yatchmink, Y., Viscidi, E. W., Jones, R. N., & Morrow, E. M. (2015). Female autism phenotypes investigated at different levels of language and developmental abilities. Journal of Autism and Developmental Disorders, 45(11), 3537-3549. doi:10.1007/s10803-015-2501-y [doi]
  3. Frazier, T. W., & Hardan, A. Y. (2016). Equivalence of symptom dimensions in females and males with autism. Autism: The International Journal of Research and Practice, doi:1362361316660066 [pii]