US Appeals Court Reinstates Over 500 Lawsuits Linking Tylenol to Autism, ADHD

A U.S. federal appeals court on Monday reinstated more than 500 lawsuits against Kenvue Inc., the maker of Tylenol, allowing litigation to proceed over allegations that prenatal use of the painkiller is linked to autism and attention deficit hyperactivity disorder (ADHD) in children.

The Court's Decision

The 2nd U.S. Circuit Court of Appeals in Manhattan reversed a lower court's decision from December 2024. In that initial ruling, U.S. District Judge Denise Cote had dismissed the lawsuits after excluding the testimony of the plaintiffs' expert witnesses, criticizing their scientific methodology.

The appeals court found that the district judge had improperly barred the expert testimony. This procedural victory for the plaintiffs re-opens the door for the cases, which had been consolidated from across the country, to move forward.

Implications for Kenvue and Investors

Following the court's decision, shares of Kenvue (KVUE) traded down 10 cents to $19.38 in morning trading, according to Reuters. The ruling represents a significant legal setback for the company, which was spun off from Johnson & Johnson in 2023.

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Kenvue has consistently maintained that Tylenol is safe and that its active ingredient, acetaminophen, is considered by doctors and medical societies to be the preferred treatment for pain and fever during pregnancy. Johnson & Johnson, which manufactured the product for over six decades, also defended its safety.

Legal and Scientific Context

Expert witnesses play a pivotal role in product liability lawsuits, and the admissibility of their testimony is often a key legal battle. One of the plaintiffs' experts cited in the original case was Andrea Baccarelli, Dean of the Harvard School of Public Health.

While the appeals court's decision allows the lawsuits to proceed, it does not rule on the scientific validity of the claims themselves. The source material, citing Reuters, notes that there is no firm scientific evidence establishing a causal link between Tylenol use during pregnancy and autism or ADHD.