October 9, 2025
3 minute read
RFK Jr. claims that using Tylenol in circumcision causes autism. Here's why this statement is wrong
Research suggesting circumcision rates linked to autism 'riddled with flaws'
RONALDO SCHEMIDT/AFP/Getty Images
Today at a government meeting, US Secretary of Health and Human Services Robert F. Kennedy Jr. said there is a link between autism and circumcision. “There are two studies that show that children who are circumcised at an early age have twice the rate of autism. This is very likely because they are given Tylenol,” he said, without citing the studies.
Kennedy probably meant 2013 study eight countries and 2015 study from Denmark, both of which claimed to demonstrate a connection between circumcision and autism level. Helen Tager-Flusberg, an autism researcher and professor emeritus at Boston University, calls the methods used in these studies “horrible.” Tager-Flusberg heads the Coalition of Autism Scientists, a group that advocates for high-quality autism research.
None of the studies have found a causal link between circumcision (or the pain medications often prescribed during the procedure) and higher rates of autism. In the more than ten years since each was published, autism researchers came under fire these studies. After examining both studies, scientists last year found there is no evidence to support the claim that circumcision causes autism or any other adverse psychological effects.
About supporting science journalism
If you enjoyed this article, please consider supporting our award-winning journalism. subscription. By purchasing a subscription, you help ensure a future of influential stories about the discoveries and ideas shaping our world today.
There is also very little evidence it gives acetaminophen (sold under the brand name Tylenol) in infants and children increases their risk of being diagnosed with autism. As the Secretary of Health and Human Services recently suggested, there is very little evidence that acetaminophen taken during pregnancy increases the risk of developing autism in a child.
In a 2013 study, researchers compared circumcision rates in eight countries, including the United States, with autism prevalence rates. They found that countries with higher rates of autism tend to have higher rates of circumcision. “They're looking at an association that includes a sample of eight countries” (an extremely small number to make such a connection), “and they're not taking into account any other factors about those countries,” says Tager-Flusberg. Factors such as average age of parents in every country, and genetics are also known to influence the rate of autism. Autism awareness and diagnostic methods also vary from country to country. All of these factors could explain the correlation, but they were not included in the analysis. “I’m ashamed that there are colleagues in my field who actually went out and did such an unreliable study that was actually published,” says Tager-Flusberg.
Experts say the level of circumcision is not a reliable substitute for acetaminophen use in infants anyway. The researchers of the 2013 study explained that they decided to look at circumcision because acetaminophen is often prescribed after the procedure. The drug is commonly taken for numerous childhood conditions and is not always prescribed for circumcision. This means relying on circumcision to assess acetaminophen use in newborns is misleading, Tager-Flusberg says.
Researchers conducting a 2015 study looked at autism rates among 3,347 boys, mostly Jewish and Muslim, who were ritually circumcised in a hospital or physician's clinic. This study found a higher likelihood of being diagnosed with autism among this group than among those who were not circumcised. “This study is riddled with shortcomings that other wrote,” psychologist David S. Mundell said in a statement sent to Scientific American on behalf of the Coalition of Autism Scientists. It had a small sample size, which limited the power of its findings, and it did not account for many Muslim circumcisions that are not performed by doctors, which likely skewed the results. The association between circumcision and autism was significant only for children aged 0 to 4 years, and not for children aged 5 to 9 years, suggesting an alternative explanation for the results.
Such observational studies are inherently limited: even if they show an association between two variables, they cannot explain what causes it. Relying on such weak evidence to make claims about the causes of autism is “terribly alarming,” Tager-Flusberg continues, and ends up confusing and worrying for families.
It's time to stand up for science
If you liked this article, I would like to ask for your support. Scientific American has been a champion of science and industry for 180 years, and now may be the most critical moment in that two-century history.
I was Scientific American I have been a subscriber since I was 12, and it has helped shape my view of the world. Let me know always educates and delights me, instills a sense of awe in front of our vast and beautiful universe. I hope it does the same for you.
If you subscribe to Scientific Americanyou help ensure our coverage focuses on meaningful research and discovery; that we have the resources to report on decisions that threaten laboratories across the US; and that we support both aspiring and working scientists at a time when the value of science itself too often goes unrecognized.
In return you receive important news, fascinating podcastsbrilliant infographics, newsletters you can't missvideos worth watching challenging gamesand the world's best scientific articles and reporting. You can even give someone a subscription.
There has never been a more important time for us to stand up and show why science matters. I hope you will support us in this mission.
