On Monday, the Trump administration, alongside its highest federal health officials, initiated a sweeping challenge to the prevailing scientific understanding of autism. They asserted, without presenting any new evidence, that acetaminophen – the active ingredient found in the widely used pain reliever Tylenol – is a direct cause of this neurological disorder.
Key officials, including Health Secretary Robert F. Kennedy Jr. and FDA Commissioner Dr. Marty Makary, further promoted leucovorin, a B-vitamin-based drug, as an autism treatment. This drug, however, has only undergone studies involving a handful of participants, raising questions about its broad applicability.
Additionally, they unveiled plans for new research into autism’s fundamental causes, allocating millions in federal funding to investigate environmental factors. This includes revisiting the long-discredited theory that vaccines contribute to the disorder.
Collectively, these declarations signal a significant shift in how autism is being publicly presented. The administration is attempting to redefine it as a neglected epidemic, primarily driven by environmental factors that, they suggest, have been ignored by politically motivated researchers. This contrasts sharply with the scientific consensus, which points to autism as a complex neurological condition influenced by both genetic predispositions and environmental elements.
The White House briefing was characterized by President Trump offering medical advice that often lacked scientific backing, mirroring tactics from his previous term where he advocated for unproven Covid treatments.
During the event, the President issued stark and repeated warnings to avoid Tylenol, directly contradicting major medical organizations. He implored pregnant women to ‘tough it out’ through pain, advising against the medication except in critical situations like extreme fever.
For many years, scientists have explored a potential link between acetaminophen and autism, but current research remains inconclusive. In response, established medical organizations promptly reaffirmed acetaminophen’s safety for pregnant women with fevers, emphasizing its use should not be long-term.
Although Mr. Kennedy acknowledged autism as a ‘multi-factorial’ condition, he quickly shifted focus to vaccines, a subject he has consistently implicated in the increasing rates of childhood autism. Both he and Mr. Trump criticized past health administrations, alleging they deliberately ignored vaccine-related risks and disregarded genetic research pertaining to the neurodevelopmental disorder.
Despite these claims, numerous studies conducted over the past thirty years have consistently found no connection between vaccines and autism. The overwhelming scientific consensus is that this theory has been thoroughly disproven.
President Trump highlighted his ongoing discussions with Mr. Kennedy regarding a potential vaccine link. He further echoed Kennedy’s concerns, suggesting that the current childhood immunization schedule ‘overwhelms’ children with an excessive number of vaccines. The President stated, without providing any evidence, that infants are receiving up to 80 different injections.
Trump asserted, ‘It’s too much liquid, too many different things are going into that baby at too big a number.’
In contrast, the Food and Drug Administration 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, describing the issue as ‘an ongoing area of scientific debate.’
External experts, when questioned about the FDA’s letter, confirmed that it does not alter standard medical protocols, which already recommend minimizing all medication use during pregnancy, including acetaminophen.
Dr. Nathaniel DeNicola, an environmental adviser to the American College of Obstetricians and Gynecologists, explained, ‘Doctors have always approached medications in pregnancy by using it only when indicated, lowest dose, for the shortest duration.’
He clarified that this principle extends to Tylenol, stating, ‘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 letter to physicians regarding the definition of ‘low-grade fever,’ for which acetaminophen use was suggested.
Medical professionals 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 choices for managing pain or fever during this period.
Given its widespread use, acetaminophen has long been a subject of concern regarding potential developmental issues in children. However, scientists largely concur that autism stems from a intricate combination of genetic and environmental influences, and that the increasing diagnosis rates cannot be attributed solely to a single cause.
During the 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 analyzed existing studies without performing its own birth outcome analysis, suggested evidence of a connection between prenatal acetaminophen exposure and neurodevelopmental conditions such as ADHD and autism.
Dr. Makary asserted at the news conference that Dr. Andrea Baccarelli, Dean of Harvard’s public health school and a co-author of the review, had indicated a causal relationship between acetaminophen and autism.
However, other contributors to the review clarified that their findings do not establish a direct cause-and-effect link between the pain reliever and autism.
Dr. Diddier Prada, a Mount Sinai epidemiologist and the study’s lead author, previously told The New York Times, ‘We cannot answer the question about causation — that is very important to clarify.’
Research into the potential risks of acetaminophen to fetal brain development has yielded inconsistent results. The comprehensive review analyzed 46 studies on the link between prenatal acetaminophen use and childhood neurodevelopmental issues, with eight specifically focusing on autism. Over half of these studies reported a positive association.
Many prominent health organizations, including the Food and Drug Administration and its European counterparts, have examined the available evidence and concluded that the findings are inconclusive, indicating no established risk.
Nevertheless, a segment of the scientific community advocates for a precautionary approach, suggesting that healthcare professionals should inform pregnant women about the potential, though unconfirmed, link between acetaminophen and autism.
Most experts agree that conducting direct pharmaceutical trials on pregnant women would be unethical. Consequently, existing research on acetaminophen’s effects relies on observational studies, where researchers track pregnancy data and subsequent child development over time.
This observational nature means researchers cannot fully account for all the variables that might distinguish pregnant women who use Tylenol from those who don’t.
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 influence a perceived connection.
He further emphasized, ‘And the biggest elephant in the room here is genetic confounding, because we know autism, A.D.H.D. 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 association between mothers who used acetaminophen and the occurrence of autism, ADHD, and intellectual disability. However, this link vanished when a follow-up analysis compared siblings born to the same mothers.
Dr. Lee concluded that the sibling study’s findings suggest maternal genetics, rather than acetaminophen, could be the underlying cause.
Kenvue, the company responsible for Tylenol, firmly dismissed any alleged connection between its product’s use during pregnancy 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 added, ‘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 roughly 600 other products. 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 its other consumer brands to a new entity named Kenvue.
The FDA also announced on Monday 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, specifically highlighting a study where approximately 40 children receiving the medication were compared to 40 on a placebo. The FDA claimed this study demonstrated ‘substantial improvement.’ This drug’s approval targets individuals with ‘cerebral folate deficiency,’ a specific subtype of autism.
GSK, the original marketer of leucovorin in the 1980s and 90s, confirmed its intention to update the drug’s labeling as requested by the FDA, to include safe usage recommendations for individuals with autism.
It’s already standard advice for pregnant women to take folic acid early in pregnancy to support healthy fetal brain development.