(NEW YORK) — A federal appeals court is deciding whether to revive more than 500 lawsuits filed by parents who claimed their children’s autism or attention deficit hyperactivity disorder (ADHD) was caused by prenatal exposure to Tylenol.
The lawsuits were dismissed in December 2023 by U.S. District Judge Denise Cote after finding that the plaintiffs’ scientific experts did not provide credible evidence linking use of Tylenol, or its active ingredient acetaminophen, to autism or ADHD.
Cote wrote in her ruling that “the unstructured approach adopted by the plaintiffs’ experts permitted cherry-picking, allowed a results-driven analysis, and obscured the complexities, inconsistencies, and weaknesses in the underlying data.”
However, in a hearing this week, two judges of a three-judge panel on the U.S. Court of Appeals for the Second Circuit in Manhattan suggested some of the experts’ testimony may have been admissible and that the lawsuits were prematurely dismissed.
“I’m having trouble understanding why the district court was correct to say that this just is nonsense. This is something that no one should hear,” Circuit Judge Gerard Lynch said during the hearing earlier this week. “It just goes out the window, when it seems to me that you have a reputable scientist explaining why each of these judgment calls was made.”
Meanwhile, Circuit Judge Guido Calabresi implied that the cases could have gone to a jury.
“It seems to me you’re constantly coming back to where you began, which is [the experts] didn’t show that there was a causal link, but a causal link cannot be shown,” Calabresi said. “All that matters is if people bring in evidence, so that then juries or courts may say, ‘This goes one way or the other.'”
The topic has been in the headlines since the Trump administration announced in September that the use of Tylenol during pregnancy may be linked to an increased risk of autism and that pregnant women should limit their use, contradicting medical evidence.
Studies on this question have not shown a direct cause and effect. Some studies point to a possible link, but major medical groups, including the American Academy of Pediatrics and the American College of Obstetricians and Gynecologists, have evaluated the evidence and continue to recommend acetaminophen as the safest pain reliever during pregnancy in consultation with your OB-GYN.
At the time of Trump’s announcement, federal officials cited an August 2025 meta-analysis from researchers at Mt. Sinai, Harvard T.H. Chan School of Public Heath, UCLA Fielding School of Public Health and UMass Lowell that found prenatal exposure to acetaminophen may be associated with an increase in rates of neurodevelopmental disorders, including autism and ADHD, in children.
However, an April 2024 study, funded by the National Institutes of Health (NIH) and published in JAMA, found that using acetaminophen during pregnancy was not linked to an increased risk of autism, ADHD or intellectual disability in children.
Additionally, a review published earlier this month in the BMJ similarly found no clear evidence of a link between acetaminophen use in pregnancy and autism or ADHD in children.
Last month, Texas Attorney General Ken Paxton sued the makers of Tylenol –Johnson & Johnson and Kenvue — claiming that they deceptively marketed the over-the-counter medication to pregnant women despite alleged links to autism and other disorders.
Johnson & Johnson sold the drug for decades and its consumer health division spinoff, Kenvue Inc., has been selling the drug since 2023. Multinational consumer goods and personal care corporation Kimberly Clark recently announced plans to acquire Kenvue.
Kenvue has defended against claims that its products, or its active ingredient, is linked to autism.
In a statement to ABC News in September, the company said it believes research shows that acetaminophen does not cause autism.
“We strongly disagree with any suggestion otherwise and are deeply concerned with the health risk this poses for expecting mothers,” the statement read. “Acetaminophen is the safest pain reliever option for pregnant women as needed throughout their entire pregnancy. Without it, women face dangerous choices: suffer through conditions like fever that are potentially harmful to both mom and baby or use riskier alternatives.”
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