The Trump administration unveiled highly contentious conclusions about the causes of autism, together with a push for research purporting to find a possible “cure” for the condition on Monday.
After months of widely trumpeted investigations spearheaded by the health secretary, Robert F Kennedy Jr, Donald Trump announced that pregnant women should limit their use of acetaminophen, usually branded as Tylenol in the US, which he claimed heightens the risk of autism when it used by pregnant women, an assertion hotly contested by scientists internationally and contradicted by studies.
Speaking from the White House, flanked by Kennedy, the president said he had “waited for 20 years for this meeting” and added: “It’s not that everything’s 100% understood or known, but I think we’ve made a lot of strides.”
But he declared: “Taking Tylenol is not good … All pregnant women should talk to their doctors about limiting the use of this medication while pregnant.”
Later, he reinforced the comment, saying: “Don’t take Tylenol. There’s no downside.”
He also spoke about upcoming recommendations that vaccines such as the measles, mumps, rubella and varicella (MMRV) shots should be given in a delayed manner or in smaller doses, despite limited evidence of the impacts. And he spoke about the hepatitis B shot, currently given to newborns as part of the national vaccine standards, and possible recommendations to delay the first dose – again with limited evidence.
Kennedy followed, announcing that the health department and US Food and Drug Administration would work to change the label on acetaminophen risks.
Administration officials also unveiled a plan to further investigate how a possible treatment for autism might exists in the shape of leucovorin, a drug currently used for patients with cancer and anemia.
Trump, who has frequently voiced his concern over autism, said, along with Kennedy, that the US is suffering from an “epidemic”, and had flagged the major initiative on Sunday at Charlie Kirk’s memorial in Arizona.
“Tomorrow we’re going to have one of the biggest announcement[s] … medically, I think, in the history of our country,” he said. “I think you’re going to find it to be amazing. I think we found an answer to autism.”
One in 31 children aged eight had a diagnosis of autism spectrum disorder (ASD) – a condition denoting communication and social difficulties, along with repetitive behaviors – in the US in 2022, according to the Centers for Disease Control and Prevention (CDC). That compares to about one in 150 in 2000.
Kennedy, who previously peddled the theory that the condition is caused by vaccinations, has attributed the rise to “environmental toxins”.
He told Monday’s event that the National Institutes of Health had been guilty of focusing “almost solely on political safe and entirely fruitless research” about autism’s causes. He said was committed to investigating the “ideology of the autism outbreak”.
He called autism “a complex condition with a multi-factual ideology”.
“One area we are currently examining is vaccines,” said Kennedy, who has frequently floated theories that the increase in the condition’s prevalence is fueled by vaccinations.
However, specialists say the increase is mainly due to increased screening, combined with evolving definitions of the disorder. They have also said the causes are predominantly dictated by genetics.
Scientists in the US and UK reacted to the Tylenol link sceptically, with British physicians denouncing it as “fearmongering” that risked stigmatising parents of children with autism.
Alison Singer, president and founder of the Autism Science Foundation, voiced scathing criticism of the administration’s approach – specifically its assertions on Tylenol, which she called “not scientifically based”.
“Any association between Tylenol and autism is based on very limited, conflicting and inconsistent science, and it’s premature to make this kind of unsubstantiated claim and risk undermining public health,” she said.
“It’s misleading to families who deserve clear more factually based information.”
She also questioned the basis of the White House announcement. “We’re uncertain as to why this press conference is being held today. To our knowledge, there was no new data that were uncovered, no new studies published, no new presentations were made. There wasn’t a scientific conference or a medical conference,” Singer said.
Speaking on a call organized by Defend America Action, a campaign group, Debra Houry, a former chief medical officer and deputy director at the CDC, told journalists: “As of three weeks ago, we hadn’t seen evidence that acetaminophen was linked with autism, so it’s curious to know how quickly that was developed.”
“There are many studies which refute a link, but the most important was a Swedish study of 2.4m births published in 2024 which used actual sibling data and found no relationship between exposure to paracetamol [known in the US as acetaminophen] in utero and subsequent autism, ADHD or intellectual disability,” said Dr Monique Botha, associate professor in social and developmental psychology at Durham University
“The fearmongering will prevent women from accessing the appropriate care during pregnancy.
US medical practitioners also cast doubt on the putative link with acetaminophen.
Dan Jernigan, another former CDC career scientist and former director of the national center for emerging and zoonotic infectious diseases, criticised Kennedy’s efforts.
“We were all asked to be a part of autism studies and to put together [an autism plan],” he said. We helped develop some of that. But then over time, what we saw was [Kennedy] having an increasingly top down approach, essentially ‘my way or the highway,’ with no regard again for the scientific processes.”
Some researchers have also pleaded caution on hopes for leucovorin, which has been reportedly shown in some tests to trigger marked improvements in the speaking and understanding ability of some people with autism.
Irva Hertz-Picciotto, an epidemiologist and autism specialist at the University of California, Davis, told the Washington Post that unrealistic expectations could lead to a loss of trust.
“I worry that it feels like everything is now tainted that comes out of the current administration,” she said.
Bruce Mirken, communications co-chair of Defend Public Health, poured cold water on the announcements in advance. “While we don’t know what he will claim today, we do know that Kennedy has a history of false statements related to autism and that the scientific evidence shows there is no ‘autism epidemic’,” he said.
Additional reporting by Melody Schreiber and agencies
