UC Davis autism research miscast in Robert F. Kennedy Jr.’s remarks on ‘epidemic’
AI-generated summary reviewed by our newsroom.
- Robert F. Kennedy Jr. cited UC Davis research to claim an autism epidemic.
- UC Davis studies show diagnosis criteria shifts explain some, not all, increases.
- Researchers caution against oversimplified claims and misuse of early findings.
Researchers at the University of California, Davis, found themselves thrust into the spotlight Monday when U.S. Health and Human Services Secretary Robert F. Kennedy Jr. and others in the Trump administration pointed to their studies as proof that America faces an autism “epidemic.”
The timing was charged. In April, the U.S. Centers for Disease Control and Prevention reported that one out of every 31 8-year-olds at 16 federal surveillance sites had been diagnosed with autism spectrum disorder — up from one out of 36 in 2020.
Kennedy and President Donald Trump linked that growing prevalence to pregnant women’s use of Tylenol, known generically as acetaminophen. And when one reporter at the White House asked whether better screening could explain the increase, Kennedy flatly rejected the idea. UC Davis research, he said, “completely debunks” that possibility.
But has it? The Sacramento Bee reviewed UC Davis’ studies cited in national coverage and questioned researchers about what their findings actually show.
What Kennedy claimed about autism
Asked whether diagnostic breakthroughs could explain any increased prevalence of autism, Kennedy called that notion “one of the canards that has been promoted by the industry for many years.” He insisted, “study after study ... completely debunks that, one of them by the MIND Institute at UC Davis.”
He described the rise in the prevalence of autism cases as an epidemic and said the National Institutes of Health, the CDC and other federal agencies would explore all potential causes, including toxic and pharmaceutical exposures.
What the 2002 UC Davis report found
The MIND Institute made national headlines in 2002 with a legislatively commissioned pilot study. Researchers examined whether the sharp increase in children with autism served by California’s Department of Developmental Services could be explained by shifting definitions, migration or misclassification.
Their answer: Loosening diagnostic criteria did not explain the rise. The study suggested the increase was real, though it stopped short of naming a cause. Multiple factors — including genetics, environment and improved detection — could be at play.
In 2005, a trio of researchers — Morton Ann Gernsbacher, Michelle Dawson, and H. Hill Goldsmith — criticized the report as “imprudent and unjustified,” arguing there was “no sound scientific evidence” that prevalence increases represented anything other than broadened criteria.
In a statement emailed to The Bee, the MIND Institute said: “The 2002 report was a preliminary survey, not a peer-reviewed study. It laid groundwork for later peer-reviewed research, but due to additional changes in the diagnostic criteria for autism, it is not a current scientific reference.”
What later UC Davis research concluded
A 2009 study led by UC Davis researchers Irva Hertz-Picciotto and Lora Delwiche took a more rigorous approach. They found that earlier diagnoses and inclusion of milder cases explained up to 33% of the increase in autism — but not all of it.
The study did not call autism an epidemic. Instead, it highlighted the complexity of the trend: multiple forces were at work, and some remained unmeasured.
Leaders at the MIND Institute later emphasized that the 2009 findings were based on the best data available at the time. Since then, diagnostic criteria have changed again, rendering those estimates outdated.
What UC Davis says today
Responding to Kennedy’s remarks, the MIND Institute issued a statement:
On Tylenol: Some studies suggest a possible link, but they fail to account for confounding factors such as why the drug was taken in the first place. Meanwhile, acetaminophen use in pregnancy has stayed flat or declined, even as autism diagnoses have risen. “If there was a link between these, we would expect both to go up or both to go down together,” the institute noted. Untreated fever, they stressed, poses real risks to both mother and fetus.
On Leucovorin: Kennedy and Trump promoted the folinic acid cancer drug adjunct as a treatment for autism. UC Davis researchers countered that evidence is far too thin to make that claim.
The institute underscored that autism has no single known cause. Current science points to an interplay of genetic and environmental factors, with no consensus on how much each contributes. Environmental factors being studied include air pollution, pesticides, plastics, metals and more.
“Our role is to conduct rigorous research,” MIND Institute researchers said in their email. “We can’t quantify how often research is misinterpreted, and we can’t control how others choose to talk about it.”
By framing old research as evidence of an epidemic, leaders of the Autism Science Foundation said, Kennedy risks confusing families and undermining trust in science.
This story was originally published September 26, 2025 at 12:47 PM.
