President Trump, alongside senior federal health officials, ignited controversy on Monday by challenging the established understanding of autism. They asserted, without presenting new evidence, that acetaminophen, the key ingredient in the popular painkiller Tylenol, is a cause of the developmental disorder.
These officials, notably Health Secretary Robert F. Kennedy Jr. and Food and Drug Administration Commissioner Dr. Marty Makary, further endorsed leucovorin, a B-vitamin-based drug, as an autism treatment. This recommendation comes despite the drug having been studied in only a limited number of research participants.
Additionally, new federally funded research was announced to investigate the fundamental causes of autism. This initiative, backed by millions of dollars, aims to explore environmental factors, including the long-discredited theory linking vaccines to the disorder.
Collectively, these announcements represent a significant shift, attempting to reframe autism as an overlooked epidemic primarily driven by environmental factors—a perspective they suggest previous “politicized” research has ignored. However, the majority of scientists maintain that autism is a neurological disorder arising from an intricate combination of genetic and environmental influences.
The White House briefing itself was characterized by President Trump offering medical advice that often lacked substantiation, echoing instances from his first term where he promoted unproven Covid treatments.
On Monday, the President issued stark warnings, directly contradicting advice from prominent medical organizations. “Don’t take Tylenol. Don’t take it. Fight like hell not to take it,” he urged, advising pregnant women to “tough it out” through pain, unless facing severe conditions like a dangerously high fever.
For many years, scientists have investigated a possible link between acetaminophen and autism, yet current studies remain inconclusive. In response, mainstream medical organizations swiftly reaffirmed acetaminophen’s safety for pregnant women experiencing fever, provided it’s not used long-term.
While Mr. Kennedy acknowledged autism as a “multi-factorial” disease, he promptly focused on vaccines. He has consistently claimed that vaccines are at least partially responsible for the increasing rates of autism in children. Both he and President Trump accused past health administrations of deliberately ignoring vaccine risks and dismissed genetic research into the neurodevelopmental disorder.
However, numerous studies conducted over the past three decades have consistently found no link between vaccines and autism. The scientific community widely considers this theory debunked.
President Trump revealed that he and Mr. Kennedy had long debated a potential vaccine connection. He further amplified Mr. Kennedy’s stance, asserting that the current childhood immunization schedule “loads up” children with an excessive number of vaccines. The President claimed, without providing evidence, that infants receive up to 80 shots simultaneously.
In stark contrast, the Food and Drug Administration adopted a much more cautious approach. On Monday, they issued a letter to doctors, accurately stating that “a causal relationship has not been established” between acetaminophen and autism and described the issue as “an ongoing area of scientific debate.”
External experts, when questioned about the letter, clarified that it does not alter standard medical practice. Existing guidelines already recommend minimizing the use of all medications, including acetaminophen, during pregnancy.
Dr. Nathaniel DeNicola, an advisor to the American College of Obstetricians and Gynecologists specializing in environmental issues, emphasized: “Doctors have always approached medications in pregnancy by using it only when indicated, at the lowest dose, and for the shortest duration.”
“This principle applies to Tylenol tomorrow as it does today, and as it did yesterday. The standard of care dictates using medications during pregnancy only when absolutely necessary and with careful discretion,” Dr. DeNicola explained.
Dr. DeNicola also highlighted that while the FDA’s letter suggested acetaminophen for low-grade fevers, it failed to clarify the specific temperature range that constitutes a “low-grade” fever.
Medical professionals advise treating fevers in pregnancy (defined as anything above 100.4 degrees Fahrenheit) due to potential risks to both the mother and fetus, including neurodevelopmental concerns. Acetaminophen is widely regarded as one of the safest available options for managing pain or fever during this period.
Given its extensive use, acetaminophen has long been subject to concerns regarding developmental problems in children. However, scientists largely concur that autism stems from a complex interplay of genetic and environmental factors, and the increase in autism diagnoses cannot 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 article, which analyzed existing studies without conducting new research on birth outcomes, suggested there was evidence of a connection between prenatal acetaminophen use and neurodevelopmental disorders such as ADHD and autism.
Dr. Makary asserted at the news conference that the dean of Harvard’s public health school, a co-author of the review, had indicated the study pointed to a causal relationship between the pain reliever and autism.
Nevertheless, other authors of the same review warned that their findings did not establish a direct cause-and-effect link 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, in a recent interview.
Research exploring the potential risks to fetal brain development has produced varied results. The review in question analyzed 46 studies on a possible link between prenatal acetaminophen use and childhood neurodevelopmental issues, with eight specifically focusing on autism. Over half of these studies reported a positive association.
Numerous health agencies, including the Food and Drug Administration and its European counterpart, have assessed the existing evidence and concluded that the findings are inconclusive, indicating no established risk.
Despite the lack of definitive proof, some scientists advocate for a precautionary approach, recommending that health professionals inform pregnant women about the potential, though unconfirmed, link between acetaminophen and autism.
The majority of experts agree that conducting pharmaceutical research on pregnant women is unethical. Consequently, existing studies on acetaminophen’s effects are observational, involving researchers analyzing pregnancy data and tracking children’s development over time.
This observational nature means researchers cannot fully account for all variables that might differentiate pregnant women who take Tylenol from those who do not.
Dr. Brian Lee, a professor of epidemiology at Drexel University, noted that many studies in the recent review “did not necessarily go to the greatest lengths to account for possible confounders,” referring to other factors that could explain a perceived association.
“The most significant unaddressed factor here,” he emphasized, “is genetic confounding, given that autism, ADHD, and other neurodevelopmental disorders are highly heritable.”
In 2024, Dr. Lee co-authored a significant study analyzing health records of 2.5 million Swedish children. Although an initial analysis found a small positive association between maternal acetaminophen use and the incidence of autism, ADHD, and intellectual disability, this link vanished when comparing siblings born to the same mothers.
The sibling study’s results suggested that maternal genetics, rather than acetaminophen, could be the underlying cause of the observed association, according to Dr. Lee.
Kenvue, the company behind Tylenol, firmly denied any connection between its product and autism during pregnancy. Melissa Witt, a spokeswoman for Kenvue, stated Monday evening, “We believe independent, sound science clearly shows that taking acetaminophen does not cause autism.”
She added, “We strongly disagree with any suggestion otherwise and are deeply concerned with the health risk this poses for expecting mothers and parents.”
Tylenol is the most recognizable of roughly 600 products containing the analgesic acetaminophen. A trade group for consumer health care products reports that nearly a quarter of U.S. adults use an acetaminophen-containing medicine weekly.
Tylenol has a 70-year history, primarily manufactured by Johnson & Johnson. In 2023, Johnson & Johnson divested Tylenol and other consumer brands to establish Kenvue as a new, independent company.
Separately, on Monday, the FDA announced the approval of leucovorin, an older generic drug, to manage autism symptoms in certain children. This medication, available in tablet form, has historically been used to counteract chemotherapy side effects.
The agency referenced a medical literature review, highlighting one study comparing approximately 40 children receiving the medication to 40 on a placebo. The FDA claimed this study demonstrated “substantial improvement.” Leucovorin’s approval is specifically for individuals with “cerebral folate deficiency,” a distinct subset of autism.
GSK, the drug’s marketer in the 1980s and 90s, confirmed it would update leucovorin’s labeling, as requested by the FDA, to reflect safe use for individuals with autism.
Pregnant women are already encouraged to take folic acid early in pregnancy to support healthy fetal brain development.