Federal Appeals Court Revives More Than 500 Lawsuits Linking Tylenol to Autism

A federal appeals court on Monday reinstated more than 500 private lawsuits against Kenvue, the maker of Tylenol, over claims that use of the painkiller during pregnancy is linked to autism and attention deficit hyperactivity disorder in children.

The 2nd U.S. Circuit Court of Appeals in Manhattan ruled that a district court judge had improperly excluded expert testimony from three doctors presented by parents and guardians who brought the cases. The three-judge panel issued a 64-page decision authored by Circuit Judge Guido Calabresi.

Calabresi wrote that the testimony from the three doctors reflected methodologies used by other scientists and "constitute acceptable interpretations of scientific evidence where scientists may, and in fact do, disagree." The ruling sends the cases back to U.S. District Judge Denise Cote in Manhattan for further proceedings.

Cote had dismissed the private lawsuits in December 2024, criticizing the methodology of the plaintiffs' expert witnesses. Expert testimony frequently plays a central role in product liability cases of this kind.

The three doctors whose testimony was found to have been wrongly excluded were Andrea Baccarelli, dean of Harvard University's School of Public Health; Eric Hollander, a psychiatry professor at the Albert Einstein College of Medicine; and Brandon Pearson, a toxicologist at Columbia University.

"We are pleased that the panel unanimously found that our key experts reliably applied their scientific methods and principles," Ashley Keller, a lawyer for the parents, said in an email.

Kenvue, based in Summit, New Jersey, responded firmly to the ruling. "We stand behind the safety of our product and will continue to defend these cases," the company said in a statement to CNBC.

Calabresi stressed that the appeals court was not determining whether acetaminophen — the active ingredient in Tylenol — causes autism or ADHD, nor was it weighing in on whether elected officials should take additional steps to protect public health. There is no firm scientific evidence of a causal link between acetaminophen use during pregnancy and autism.

Doctors and medical societies consider acetaminophen the preferred treatment for pain and fever during pregnancy. Kenvue has long maintained that Tylenol is safe, a position shared by its former parent company Johnson & Johnson, which produced the product for more than 60 years before spinning off Kenvue in 2023.

Several major retailers and pharmacy operators were also named as defendants in the lawsuits, including CVS, Kroger, Target, Walgreens, and Walmart. Shares of Kenvue traded down 20 cents at $19.28 in morning trading on Monday.

The case comes as Kenvue is in the process of being acquired by Kimberly-Clark, the maker of Kleenex tissue products, for more than $40 billion — a deal announced last November. The revival of hundreds of lawsuits adds legal uncertainty to that transaction as it works toward completion.

The topic of a Tylenol-autism connection gained broader public attention after President Donald Trump and senior U.S. health officials suggested such a link in September, underscoring the degree to which the litigation has become entangled with broader debates over consumer product safety and federal health policy.

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