By Liz Essley Whyte

WASHINGTON -- Health Secretary Robert F. Kennedy Jr.'s team had decided by the beginning of September to tell Americans that acetaminophen, the active ingredient in Tylenol, was a possible cause of autism. But officials were divided over how much emphasis to put on the painkiller and were planning to discuss it as one of many possible causes, people familiar with the matter said.

Doctors that Kennedy had selected to lead key agencies under him -- Jay Bhattacharya, Mehmet Oz and Marty Makary -- suggested the big story should be leucovorin, a little-known generic drug in which they saw promise for alleviating autism symptoms.

But a meeting with Tylenol's maker convinced Kennedy to put the emphasis on acetaminophen.

Kennedy spent the first weekend of September poring over acetaminophen studies and calling scientists. After summoning Kirk Perry, interim CEO of Tylenol manufacturer Kenvue, Kennedy's mind was set. He found Kenvue's evidence in support of the drug to be poor, and became convinced that he had a moral duty to get the word out about the risk of acetaminophen as soon as possible, the people said.

President Trump was thrilled with Kennedy's plan, the people said, even though Bhattacharya, Oz and Makary had advocated for putting the emphasis on leucovorin. Trump relished the chance to tell the world their possible reason for why one in 31 children nationwide had been diagnosed with autism, the people said. Trump for years has publicly aired his keen interest in the condition.

The top doctors agreed generally that acetaminophen was worth warning women about, and that the evidence pointed to the need to be cautious with the drug.

The result was the explosive White House news conference Monday, when the president laid out in no uncertain terms that pregnant women should avoid Tylenol ("Don't take it"), despite the mixed evidence linking the painkiller to autism. The event stunned many of the nation's doctors and public health experts, some of whom called Trump's actions dangerous.

In the end, Trump and Kennedy went with their own messaging instincts, and leucovorin became more of an afterthought. Trump didn't mention it by name at the press conference, giving only a passing mention to a new label for "an existing drug" that may help alleviate autism symptoms. "That's one of the things that I'm very, very happy about," he said.

"President Trump pledged to address America's skyrocketing rates of autism, and his team is deploying Gold Standard Science to deliver on this pledge," White House press secretary Karoline Leavitt said.

A spokesman for the Department of Health and Human Services said: "HHS' actions mark historic progress in tackling the autism epidemic -- just as Secretary Kennedy promised."

Some studies have shown a potential link between acetaminophen and autism, such as a 2020 Johns Hopkins study cited by administration officials. But other studies found no link, including a 2024 study of 2.4 million Swedish children that found no association between acetaminophen and autism. Professional societies representing obstetricians continue to say pregnant women should use acetaminophen to treat pain and fever.

"The facts are that over a decade of rigorous research, endorsed by leading medical professionals and global health regulators, confirms there is no credible evidence linking acetaminophen to autism," a spokeswoman for Kenvue said.

Kennedy had heard for decades from mothers of autistic children who blamed Tylenol for the disorder, a person familiar with the matter said. Acetaminophen was one of the potential culprits he wanted to investigate when he launched his search for the cause of autism, the person said.

During the summer, some of Kennedy's top lieutenants grew excited about the promise of leucovorin. The drug, chemically related to vitamin B9, was typically used to ward off side effects of chemotherapy. Some early randomized, controlled studies had shown that versions of the drug helped improve communication and behavioral symptoms in some autistic people, though some autism researchers have said the studies are too small to make a sweeping recommendation of the drug.

"We have also identified an exciting therapy that may benefit large numbers of children who suffer from autism," Kennedy said at the press conference.

But he spent much of his time on Tylenol -- and vaccines.

"HHS will act on acetaminophen," he said. The Food and Drug Administration "will drive new research to safeguard mothers, children and families."

Write to Liz Essley Whyte at liz.whyte@wsj.com

(END) Dow Jones Newswires

September 24, 2025 21:00 ET (01:00 GMT)

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