Federal health officials are set to release a report on Monday that is expected to suggest a connection between the use of acetaminophen, the active ingredient in common painkillers such as Tylenol, and increasing rates of autism. While this potential link has been a subject of scientific inquiry for years, research has consistently yielded mixed results.
President Trump commented on the forthcoming report, stating on Sunday, “I think it’s a very big factor,” when referring to acetaminophen. He added, “If there’s a question — even if there’s a question — you just do it right?” during a conversation with reporters aboard Air Force One.
The agency plans to issue a caution to pregnant women, advising against acetaminophen use unless necessary for fever. Acetaminophen is currently considered one of the safest options for pain and fever during pregnancy, though doctors already routinely advise against its long-term use.
Beyond acetaminophen, the report is also anticipated to recommend leucovorin, a form of the B vitamin folate, as a potential treatment for autism. Folate has long been recognized for its role in neural development.
Concerns surrounding acetaminophen and its potential impact on childhood developmental problems are not new. However, the scientific community largely agrees that autism is a complex condition stemming from a combination of genetic and environmental factors, making it challenging to attribute rising rates to any single cause.
Just last month, a review of existing data, conducted by epidemiologists from the Harvard T.H. Chan School of Public Health and the Icahn School of Medicine at Mount Sinai, reported finding evidence of an association between acetaminophen use during pregnancy and neurodevelopmental disorders like attention deficit hyperactivity disorder (ADHD) and autism.
Studies exploring the potential risk to fetal brain development have presented conflicting findings, with some indicating a link to neurodevelopmental disorders in children, while others have found none.
Major health organizations, including the Food and Drug Administration, the European Medicines Agency, and the Society for Maternal-Fetal Medicine, have all reviewed the available evidence and concluded that the findings remain inconclusive.
Despite this, some scientists have advocated for a cautious approach, recommending that health professionals advise pregnant women about the potential, albeit unproven, link between acetaminophen and autism.
Conversely, specialists in maternal-fetal medicine have argued that such a recommendation is unwarranted given existing guidance for pregnant women to use Tylenol and other acetaminophen-containing drugs sparingly. Their concern is that women might unnecessarily avoid acetaminophen treatment when it is medically indicated.
“There’s no credible scientific link that Tylenol causes autism,” stated Dr. Nathaniel DeNicola, an advisor to the American College of Obstetricians and Gynecologists on environmental matters, adding that the studies examining this connection are “too deeply and fundamentally flawed to draw reliable conclusions.”
The authors of the most recent report themselves emphasized that their findings do not establish a cause-and-effect relationship.
“We cannot answer the question about causation — that is very important to clarify,” explained Dr. Diddier Prada, an epidemiologist at Mt. Sinai and one of the study’s authors, earlier this month. The ethical implications of conducting pharmaceutical research on pregnant women mean that all current studies on acetaminophen’s effects are observational. This methodology involves analyzing data from women’s pregnancies and tracking their children’s development over time.
Consequently, researchers face challenges in accounting for all potential differences between pregnant women who use Tylenol and those who do not.
Dr. Brian Lee, a professor of epidemiology at Drexel University, noted that many studies included in the new review “did not necessarily go to the greatest lengths to account for possible confounders,” referring to other variables that could explain an apparent link. He highlighted, “And 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 the health records of 2.5 million children in Sweden. While an initial analysis suggested a small positive association between maternal acetaminophen use and the incidence of autism, ADHD, and intellectual disability, this link disappeared when a subsequent analysis compared siblings born to the same mothers. The sibling study’s results, Dr. Lee explained, pointed towards “maternal genetics” as a more likely underlying cause, rather than acetaminophen itself.
Pregnant women are already advised to take folic acid early in pregnancy to support healthy fetal brain development; leucovorin, the form of folate expected to be recommended in the Health Department’s report, is a type of folic acid. Some studies have also hinted that folic acid supplementation might improve behavioral outcomes, including communication skills, in children with autism, though these findings are still considered preliminary.