In a striking departure from established scientific consensus, President Trump, flanked by senior federal health officials, announced a controversial new stance on autism. Without presenting new evidence, the administration claimed that acetaminophen, the active ingredient found in popular pain relievers like Tylenol, is a cause of the developmental disorder.
During the announcement, Health Secretary Robert F. Kennedy Jr. and FDA Commissioner Dr. Marty Makary also publicly supported leucovorin, a B-vitamin-based drug, as an autism treatment. This endorsement comes despite the drug having undergone only limited studies, involving merely dozens of participants.
Furthermore, the administration pledged millions in federal funding for new research into autism’s origins. This research aims to explore various environmental factors, notably revisiting the long-discredited theory that vaccines contribute to the disorder.
These combined statements represent a significant effort to reframe autism not as a complex neurological condition influenced by genetics and environment—the prevailing scientific view—but as a ‘neglected epidemic’ primarily driven by environmental factors, which, they suggest, biased researchers have overlooked for too long.
The White House briefing itself was characterized by President Trump’s frequent delivery of medical advice lacking solid scientific backing, echoing his earlier tenure when he promoted unverified treatments for COVID-19.
On Monday, the President issued stark warnings directly contradicting major medical organizations. He emphatically urged, ‘Don’t take Tylenol. Don’t take it. Fight like hell not to take it.’ He advised pregnant women to endure pain unless facing severe conditions like dangerously high fevers.
For years, scientists have explored a possible link between acetaminophen and autism, but current research remains inconclusive. In response, leading medical organizations swiftly reaffirmed acetaminophen’s safety for pregnant women experiencing fever, cautioning only against prolonged use.
While acknowledging autism as a ‘multi-factorial’ disease, Mr. Kennedy heavily emphasized vaccines, a long-standing personal focus, as a partial cause for the increased rates of autism in children. Both he and President Trump accused past health agencies of deliberately ignoring vaccine risks and dismissed genetic research into the neurodevelopmental disorder.
It’s important to note that over the past three decades, numerous studies have consistently found no link between vaccines and autism. The overwhelming scientific consensus is that this theory has been thoroughly debunked.
President Trump indicated that he and Mr. Kennedy have frequently discussed a potential vaccine connection. He further amplified Mr. Kennedy’s opinions, criticizing the childhood immunization schedule for ‘loading up’ children with too many vaccines. The President asserted, without providing evidence, that infants receive up to 80 different shots.
“It’s too much liquid, too many different things are going into that baby at too big a number,” President Trump stated.
The Food and Drug Administration, however, adopted a more cautious tone. On Monday, they issued a letter to medical professionals, accurately stating that ‘a causal relationship has not been established’ between acetaminophen and autism and describing the issue as ‘an ongoing area of scientific debate.’
External medical experts clarified that the FDA’s letter doesn’t alter existing standard practice, which already recommends minimizing all medication use during pregnancy, including acetaminophen.
Dr. Nathaniel DeNicola, an advisor to the American College of Obstetricians and Gynecologists on environmental matters, emphasized that ‘Doctors have always approached medications in pregnancy by using it only when indicated, lowest dose, for the shortest duration.’
He further explained, ‘That applies to Tylenol tomorrow the same as it does today, the same as it did yesterday. That is the standard of care: to only use medications when indicated during pregnancy and judiciously.’
Dr. DeNicola also noted a lack of clarity in the FDA’s communication, questioning how ‘low grade fevers’ – the only type for which acetaminophen use was explicitly mentioned – were defined in their guidance to physicians.
Medical professionals generally advise treating fevers above 100.4 degrees Fahrenheit during pregnancy due to potential risks to both mother and fetus, including neurodevelopmental concerns. Acetaminophen remains one of the limited safe options for pain and fever relief in pregnant women.
Given its widespread use, acetaminophen has long been scrutinized for potential links to developmental problems in children. However, the scientific community broadly agrees that autism arises from an intricate combination of genetic and environmental influences, making it unlikely that rising diagnosis rates can be attributed to a single cause.
During their announcement, health officials frequently referenced a recent scientific review conducted by epidemiologists from Harvard T.H. Chan School of Public Health and the Icahn School of Medicine at Mount Sinai.
This review, which synthesized existing research without performing new analyses of birth outcomes, suggested evidence of a connection between prenatal acetaminophen use and neurodevelopmental disorders such as ADHD and autism.
At the news conference, Dr. Makary claimed that Dr. Andrea Baccarelli, dean of Harvard’s public health school and a co-author of the review, had affirmed a causal link between the pain reliever and autism.
However, in a statement released Monday evening, Dr. Baccarelli clarified that further research is essential to establish any causal relationship. He added, ‘But based on existing evidence, I believe that caution about acetaminophen use during pregnancy — especially heavy or prolonged use — is warranted.’
Other contributing authors to the same review were quick to emphasize that their findings do not confirm a cause-and-effect relationship between acetaminophen and autism.
“We cannot answer the question about causation — that is very important to clarify,” stated Dr. Diddier Prada, an epidemiologist at Mount Sinai and the study’s lead author, earlier this month.
Research into acetaminophen’s potential risks to fetal brain development has produced mixed results. The recent review analyzed 46 such studies on prenatal acetaminophen use and childhood neurodevelopmental issues, including eight specifically on autism, with over half showing a positive association.
Nonetheless, many prominent health organizations, such as the Food and Drug Administration and its European counterparts, have examined the available data and concluded that the evidence remains inconclusive, meaning no established risk has been confirmed.
Despite this, some scientists advocate for a precautionary approach, suggesting health professionals advise pregnant women about a possible link between acetaminophen and autism.
Ethical concerns generally prohibit pharmaceutical research directly on pregnant women. Consequently, existing studies on acetaminophen’s effects are observational, involving researchers analyzing data from pregnancies and tracking children’s development over time.
This observational nature means researchers cannot fully account for all variables that might distinguish pregnant women who use Tylenol from those who don’t.
Dr. Brian Lee, a professor of epidemiology at Drexel University, commented that many studies in the review ‘did not necessarily go to the greatest lengths to account for possible confounders,’ referring to other influential factors.
He added that ‘the biggest elephant in the room here is genetic confounding, because we know autism, ADHD, and other neurodevelopmental disorders are highly heritable.’
In 2024, Dr. Lee co-authored a significant study examining health records of 2.5 million Swedish children. Initially, it showed a minor positive correlation between maternal acetaminophen use and autism, ADHD, and intellectual disability. However, this link vanished when a follow-up analysis compared siblings born to the same mothers.
The sibling study’s findings suggested that maternal genetics, rather than acetaminophen, could be the underlying cause.
Kenvue, the manufacturer of Tylenol, firmly refuted any connection between prenatal use of its product and autism. Melissa Witt, a Kenvue spokeswoman, stated Monday evening, ‘We believe independent, sound science clearly shows that taking acetaminophen does not cause autism.’
She further emphasized, ‘We strongly disagree with any suggestion otherwise and are deeply concerned with the health risk this poses for expecting mothers and parents.’
Acetaminophen, an analgesic, is the active ingredient in Tylenol and approximately 600 other products. A consumer healthcare trade group reports that nearly a quarter of U.S. adults use an acetaminophen-containing medicine weekly.
Tylenol has a 70-year history, primarily produced by Johnson & Johnson until 2023, when it and other consumer brands were spun off to the new company, Kenvue.
Separately, on Monday, the FDA also announced the approval of leucovorin, an older generic drug, for treating autism symptoms in certain children. This tablet-form medication has historically been used to manage chemotherapy side effects.
The agency referenced a medical literature review, particularly highlighting one study involving roughly 40 children on the medication versus 40 on a placebo, which they stated demonstrated ‘substantial improvement.’ The drug’s approval is specifically for individuals with ‘cerebral folate deficiency,’ a distinct subgroup within the autism spectrum.
GSK, the former marketer of leucovorin in the 1980s and 90s, confirmed it would update the drug’s labeling as requested by the FDA to reflect its safe use for individuals with autism.
It is already common practice for pregnant women to be advised to consume folic acid early in pregnancy, which is known to support healthy fetal brain development.