Health and Human Services Secretary Robert F. Kennedy Jr. criticized the media this week for its coverage of statements he made at President Trump’s cabinet meeting on Thursday, in which he linked Tylenol (acetaminophen), given to infant boys after circumcision, to autism. Doubling down a day later, he insisted there is a connection, even adding hypotheses on the supposed causal process. Kennedy’s repeating refuted (or at least disputed) links isn’t a one-off. He has often done this regarding exposure to substances such as acetaminophen, thimerosal and aluminum salts that he thinks are tied to autism.
In the cabinet meeting, Kennedy stated that studies show children who are circumcised early have double the rate of autism and it’s “highly likely because they’re given Tylenol.” While “this is not proof,” he said, “we’re doing the studies to make the proof.”
It’s unclear whether he meant his department is conducting new studies or citing already existing publications. In his post a day after the cabinet meeting, he defended himself against what he called “mainstream media attacks” by citing a recent pre-print that raises concern about acetaminophen exposure in infancy.
Pre-print papers are not peer-reviewed. And the one Kennedy referred to isn’t primary research. It’s a review article that appears focused on suggesting that acetaminophen is a primary causal driver of autism, to the virtual exclusion of other environmental or genetic factors. The authors conducting the review seem to approach the examined literature through that filter.
Kennedy also implicitly referred to a 2015 Danish national cohort study published in the Journal of the Royal Society of Medicine. Among boys born between 1994 and 2003, those who were circumcised were more likely to develop autism spectrum disorder.
What Kennedy did not divulge was that the study authors acknowledged numerous limitations, including the fact they had no data on whether acetaminophen was actually administered during the circumcisions. The researchers wrote that while their evidence was “compatible with a possible causal role of circumcision trauma in some cases of autism spectrum disorder,” they warned that “no firm conclusions should be drawn at this point.” They subsequently called for future research.
The latest reassertion by Kennedy of an unproven theory reminds us of what occurred just two weeks ago when both Trump and Kennedy suggested Tylenol may contribute to autism risk when used by pregnant women.
Multiple large-scale studies show no correlation between maternal use of acetaminophen and neurodevelopmental disorders in offspring, including autism.
We know from Kennedy’s vaccine-skeptic views that he also has a tendency to connect dots between substances found in vaccines and autism or other disorders and diseases. Thimerosal is one example. Vaccine makers have long used the mercury-based preservative to prevent microbial growth. Though the substance was removed from most vaccines more than 20 years ago, experts don’t consider thimerosal unsafe. Yet Kennedy has linked it to autism. His new handpicked Advisory Committee on Immunization Practices voted against flu shots containing thimerosal, despite lack of evidence of negative health effects. This only impacts a relatively small percentage (4%) of flu vaccines administered to Americans as the vast majority of shots don’t contain thimerosal.
And this summer, Kennedy said he wanted to examine aluminum in vaccines. Speaking to governors on July 26th, Kennedy stated “we need to look at the aluminum in the vaccines to see if that has anything to do with this explosion of allergies that began in 1989, which was the year they expanded the vaccine schedule.” Aluminum salts are included in many vaccines as an adjuvant to boost the immune response. Should ACIP at some point recommend against vaccines containing this substance, this would have a far greater impact than the thimerosal decision.
A recently published study of over one million people in Denmark found no link between aluminum and 50 chronic conditions, including autism, allergies and autoimmune diseases. Yet, in what Scientific American described as a “rare move” for a United States public official, Kennedy called for this published paper to be retracted. The journal rejected the request.
Confounding factors may be “at the root of much of what RFK Jr. cites and claims,” said physician and medical journalist, Celine Gounder, in an interview with CBS News. This is what happens if the relationship between an exposure, say, acetaminophen, aluminum salts or thimerosal, and an outcome (autism) is distorted by the presence of a third variable or perhaps more.
The studies Kennedy often refers to point to association and not causation. Moreover, when one properly controls for confounding factors the correlations themselves tend to disappear.