What New Autism Findings Tell Us—and What They Don't

A new study published Wednesday by JAMA Network Open confirmed trends previously reported by the Centers for Disease Control (CDC) and others: autism prevalence is increasing dramatically. The authors—most, but not all, of whom are affiliated with Kaiser Permanente—turned to electronic health records between 2011 and 2022 to track prevalence across populations sorted by age, race, ethnicity, and sex.

Given that the increase in autism prevalence has already been well established, one might wonder how this study contributes to ongoing conversations about autism diagnosis and treatment. The authors are very careful not to speculate on the implications of their findings, limiting their analysis to a strict reporting of the data. Still, these statistics support multiple important conclusions.

Racial Inequity in Autism Diagnosis Is Dropping

One of the key findings is that, while autism prevalence is rising in all children, the authors found larger increases among racial and ethnic minorities. For example, while autism prevalence in non-Hispanic children increased 146 percent between 2011 and 2022, the prevalence in Hispanic children increased 315 percent. Disproportionate prevalence increases were also reported in African American and Indigenous children.

But this is maybe, in part, good news. Researchers, clinicians, and advocates have long expressed concern over the lack of accessibility to autism diagnosis and treatment in minority communities. These findings suggest that such inequities are being addressed, at least to some degree.

“Disparities still exist in obtaining an evaluation and in access to services,” Luke Grosvenor, the study’s lead author, told me in an interview. “We’re making progress in these areas, but there’s still work to do.”

Sex Differences in Autism Diagnosis May Not Be as Great as Previously Thought

When Leo Kanner first proposed his diagnosis of infantile autism in 1943, he reported that boys were much more frequently affected than girls. Although his 4:1 ratio has been repeatedly confirmed (by Hans Asperger and others since then), some advocates and researchers have hypothesized that this disparity more accurately reflects differences in how autism presents in girls, and have suggested that girls may be better able to comport to expectations of parents, teachers, and neurotypical peers.

The Kaiser Permanante data supports this theory, to some extent. While prevalence increased 185 percent in boys between 2011-2022, it increased 305 percent in girls over the same period. By 2022, the male-female ratio dropped to 3:1.

Obviously, a significant male bias still exists that is unexplained by these data. More research is needed, particularly on poorly understood biological forces such as an alleged “female protective effect” during early development. This refers to the idea that it may take more genomic perturbations to disrupt female than male brain development.

The Elephant in the Room: Why?

That autism prevalence has been steadily increasing is not controversial, and it is not news. Hotly contested, however, is why. The Kaiser Permanente paper briefly references some of the more common explanations, including increased awareness, environmental factors, changes in screening practices, diagnostic criteria and others, but doesn’t pick a side: “We didn’t have the data to do that,” Grosvenor told me. “The goal of our study wasn’t to determine the possible causes.”

But his team’s findings do problematize some of these theories. For example, the paper reports a 352 percent increase in the number of autistic children aged 0-4 between 2011 and 2022. This is fairly recent data that tracks trends starting three years after the United Nations declared April 2 as “World Autism Day,” six years after Autism Speaks began hosting its walks all over the country, and more than 40 years after Bernard Rimland christened April “Autism Awareness Month.” By 2012, the public was so aware that The Autistic Self Advocacy Network was calling to replace “Autism Awareness” with “Autism Acceptance.” It’s very difficult to imagine there was much room for awareness to increase over the decade under study, never mind that it could increase enough to cause autism prevalence to more than quadruple in the youngest age group. Grosvenor considers this magnitude of increase too great to be accounted for by just one factor. When I ask him whether he thinks the increased prevalence might represent a real and dramatic increase in the number of autistic children, he acknowledges, “We can’t rule that out as a possibility.”

But that’s a question for a different study. For Grosvenor, the most important takeaway from his team’s work is that “there’s a growing need for expanded healthcare services and research on the growing number of autistic children and adults.” I don’t think anyone could argue with that.

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