Kennedy Makes Unfounded Claims Linking Tylenol, Circumcision to Autism

In an escalating controversy surrounding claims about Tylenol and autism, Health and Human Services Secretary Robert F. Kennedy Jr. has added new disputed assertions to the ongoing debate during an October 9 Cabinet meeting.

Kennedy claimed that studies on circumcision provide evidence linking the common pain reliever to autism in children. “There’s two studies that show children who are circumcised early have double the rate of autism, and it’s highly likely because they’re given Tylenol,” Kennedy stated during the meeting.

This follows President Donald Trump’s September 22 announcement where he advised pregnant women and parents of newborns to avoid Tylenol (acetaminophen). “Don’t give Tylenol to the baby after the baby’s born,” Trump warned.

The following day, Kennedy doubled down on social media, referencing an August 1 preprint study as providing a “rigorous scientific framework” supporting his claims. He accused mainstream media of character assassination rather than examining the scientific evidence.

Medical experts, however, strongly dispute these interpretations. The studies Kennedy cited do not directly measure acetaminophen use in relation to autism, nor do they establish a causal link between the medication and the condition.

The Danish study referenced by Kennedy, published in 2015, examined circumcision and autism rates in Denmark but did not track Tylenol use. The study’s authors explicitly acknowledged this limitation, writing they were “unable to address the [acetaminophen] hypothesis directly.”

Jeffrey S. Morris, director of the biostatistics division at the University of Pennsylvania’s Perelman School of Medicine, assessed the evidence Kennedy cited and concluded, “I don’t think either study provides any substantial evidence that [acetaminophen] use increases risk of autism.”

The preprint Kennedy used to support his claims has not undergone peer review—a crucial step in scientific validation. Its senior author, William Parker, has long advocated for the theory that acetaminophen causes autism despite limited supporting evidence.

David S. Mandell, a psychiatry professor at the University of Pennsylvania and director of the Penn Center for Mental Health, was blunt in his assessment of the preprint: “This is not science.” He noted the document starts with an unproven conclusion rather than asking a scientific question.

The Danish study Kennedy referenced examined records of nearly 343,000 boys born between 1994 and 2003, finding that circumcised boys were 46% more likely to be diagnosed with autism before age 10. However, only 3,347 boys were circumcised in medical settings, with just 57 of those receiving autism diagnoses—a very small sample from which to draw broad conclusions.

Experts point to alternative explanations for the Danish findings. Brian Lee, a professor of epidemiology at Drexel University, noted that circumcision in Denmark is rare and primarily chosen by immigrants from Muslim countries. Previous research has shown associations between immigration from low-income countries and early autism diagnoses, potentially explaining the correlation without involving Tylenol.

Mandell added that babies circumcised in hospital settings likely had other medical issues that could independently increase autism risk. “People who seek health care to get a circumcision in a hospital are also very likely to seek health care for their children,” Lee explained, suggesting these parents might be more proactive in seeking autism evaluations.

While some studies have shown associations between acetaminophen use during pregnancy and autism, this doesn’t establish causation. Medical guidance continues to recommend that pregnant people consult with their doctors when considering acetaminophen use for fever or pain—conditions that, if left untreated, could themselves pose risks.

The controversy highlights the complexity of autism research and the dangers of drawing definitive conclusions from limited or misinterpreted data, especially when communicated by high-ranking government officials.