Evidence that clinicians are missing girls with autism has been building for years. Because autistic girls tend to exhibit different traits than autistic boys do, they are frequently overlooked by teachers, doctors, and standard diagnostic tools. Those omissions carry over into the research literature, where studies typically include three to six males for every female, says William Mandy, a clinical psychologist at University College London.
As a result, researchers don’t yet know enough about gender differences in autism—and so they miss girls whose traits differ from those of boys. It’s a vicious circle, Mandy says: “You are inheriting any diagnostic bias that is built into the system.”
Read: The invisible women with autism
To break the cycle, some researchers, including Mandy, are making it a priority to recruit female and nonbinary participants into their studies. And some are turning to women such as daVanport and gender-nonconforming autistic people for guidance on how to design better studies and cast a wider net when recruiting participants. DaVanport has been an adviser on one study for more than a year. She and an autistic colleague solicit feedback from a group of about 20 autistic people, and she attends weekly meetings to share their thoughts with researchers on what it is like to be autistic beyond the typical definition.
Improving the sex and gender balance in autism studies could transform our understanding of the condition, just as it did for heart disease in women. Without that balance, says Lauren Kenworthy, who leads the team, “we certainly miss opportunities to provide effective treatment or to understand what effective treatment might be.”
Autism is often cited as being four times as common in boys as in girls. But some researchers question this statistic, saying the true ratio is likely to be less skewed because so many autistic girls go unidentified. In one study of autism diagnoses, for example, Mandy’s group found a ratio of 3 males to every 1 female.
Still, most studies cite the 4-to-1 ratio as fact, and their participant ratios are often even higher. One 2012 meta-analysis of brain-imaging studies had a ratio of 15 males for every female. Because they include so few girls and women, many studies don’t stratify their results by sex or gender, and they report their male-based conclusions as universally applicable, says Rene Jamison, a clinical associate professor at the University of Kansas in Kansas City.
In a typical trial of 50 participants that might include 10 girls, statistical analyses cannot distinguish whether the results in girls differ from those in boys. But by reporting those results as applicable to anyone with autism, scientists do a disservice both to girls, who might have different needs than boys do, and to boys, whose results might be diluted by the inclusion of girls. “To specifically look at whether a treatment differs as it applies to boys versus girls, it’s best to have an equal sample size of the two sexes,” says Meng-Chuan Lai, who studies gender and autism at the University of Toronto. “That’s something that really hasn’t been done.”