The Trump administration is planning to release a report this month that will reportedly link use of the common painkiller acetaminophen (sold under the brand name Tylenol) during pregnancy, as well as certain vitamin deficiencies, to autism spectrum disorder, despite lacking the scientific research to back up such claims.
This is just the latest controversy surrounding the actions of Health and Human Services Secretary Robert F. Kennedy Jr., who has repeated unsupported claims about autism in the past, and promised to "get to the bottom" of its cause.
The agency confirmed it is working on a report, but declined to comment on its conclusions. "Until we release the final report, any claims about its contents are nothing more than speculation," a spokesperson for HHS emailed in a statement.
There is no credible scientific evidence that acetaminophen causes autism or that leucovorin (a derivative of folic acid) can prevent the disorder, as the HHS report purportedly will suggest, according to reporting by the Wall Street Journal.
In fact, those in the medical community, including the Society for Maternal-Fetal Medicine, said in a statement that acetaminophen is safe and recommended for use in pregnancy, especially to treat fever and pain. "Untreated fever, particularly in the first trimester, increases the risk of miscarriage, birth defects, and premature birth, and untreated pain can lead to maternal depression, anxiety, and high blood pressure," the society said in its statement.
"It is disingenuous and misleading to boil autism's causes down to one simple thing," said Dr. Alycia Halladay, chief science officer at the Autism Science Foundation, in a statement. There are hundreds of genes that are linked to autism, and while there are also thought to be other complex environmental factors, the foundation says "any association between acetaminophen and autism is based on limited, conflicting, and inconsistent science and is premature given the current science."
A few small studies have suggested an association between fetal exposure to acetaminophen and the subsequent risk of diagnosis with autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD). But the largest study to date, an NIH-funded collaboration between U.S. and Swedish scientists, found no increased risk.
Even before that study was published in 2024, a U.S. District Court had reached a similar conclusion in a product liability case.
Leucovorin, also known as folinic acid, is a form of vitamin B9 (also known as folate) that is used to treat certain types of vitamin B9 deficiency that are usually caused by cancer chemotherapy. It is sometimes prescribed off-label as a treatment for autism, though the evidence that it works is scant.
The use of leucovorin is based on research suggesting that many people with autism have a metabolic difference that could reduce the amount of folate that reaches the brain. Leucovorin appears to offer a way around that metabolic roadblock.
Folate is important for brain and nervous system development, which is why pregnant women are often prescribed supplements that contain folic acid, a synthetic version of folate. Folate deficiency in a mother increases the risk of neural tube defects including spina bifida, but the link to autism is unclear.
The Autism Science Foundation said in its statement that there are four studies suggesting low folate levels in pregnant women could increase the risk of autism, but it said "this science is still in very early stages, and more studies are necessary before a definitive conclusion can be reached."
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