Hundreds of private lawsuits linking Tylenol to autism revived

Summary

• 2nd U.S. Circuit Court of Appeals revives 500+ lawsuits
• Expert testimony from Harvard dean Andrea Baccarelli allowed
• Kenvue maintains Tylenol safety amid litigation
• Lawsuits returned to U.S. District Judge Denise Cote

A federal appeals court on Monday revived more than 500 private lawsuits against Tylenol maker Kenvue over the painkiller’s alleged link to autism.

The 2nd U.S. Circuit Court of Appeals in Manhattan said a district court judge improperly excluded expert testimony from three doctors offered by parents and guardians who tied Tylenol use during pregnancy to autism and attention deficit hyperactivity disorder (ADHD) in children.

There is no firm scientific evidence of such a link. The issue drew greater attention after President Donald Trump and top U.S. health officials in September suggested a link to autism.

In a 64-page decision for a three-judge panel, Circuit Judge Guido Calabresi said the testimony from the three doctors, including the dean of Harvard University‘s School of Public Health, reflected methodologies used by other scientists, and “constitute acceptable interpretations of scientific evidence where scientists may, and in fact do, disagree.”

Calabresi stressed that the appeals court was not deciding whether using acetaminophen causes autism or ADHD, or whether elected officials should do more to protect public health.

Doctors and medical societies consider acetaminophen, the active ingredient in Tylenol, the preferred means to treat pain and fever during pregnancy.

Many retailers and pharmacy operators including CVS, Kroger, Target, Walgreens and Walmart were also named as defendants.

Kenvue defends Tylenol’s safety

In a statement on Monday, Kenvue maintained that Tylenol is safe, and said the decision “does not change the fact that credible, independent science shows no proven link between taking acetaminophen and autism or attention deficit hyperactivity disorder.”

Kenvue plans to again try to show in court that the opinions of the plaintiffs’ experts are unreliable.

In afternoon trading, Kenvue shares traded down 1.8% at $19.13, while Kimberly-Clark shares fell 2.7% to $109.34.

Johnson & Johnson, Kenvue’s former parent, made Tylenol for more than 60 years and has also defended its safety.

Kenvue agreed last November to be acquired by Kleenex tissue maker Kimberly-Clark for more than $40 billion. The transaction is expected to close this year. Kimberly-Clark did not immediately respond to requests for comment.

Harvard dean’s testimony allowed

The appeals court said the doctors whose testimony was wrongly excluded included Harvard public health dean Andrea Baccarelli; 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.

Experts often play a key role in product liability lawsuits such as the Tylenol cases.

Kenvue is based in Summit, New Jersey, and was spun off in 2023 by Johnson & Johnson.

The private lawsuits were dismissed in December 2024 by U.S. District Judge Denise Cote in Manhattan, who criticized the methodology of the plaintiffs’ expert witnesses.

Monday’s decision returns the lawsuits to Cote for further proceedings.