MDL Judge Grants Summary Judgment in All Tylenol Lawsuits Over Autism, ADHD

A U.S. District Judge has ruled that all Tylenol lawsuits brought by families of children diagnosed with attention deficit hyperactivity disorder (ADHD) or autism will be dismissed, after determining that plaintiffs cannot use a “piecemeal” approach to establish that use of acetaminophen during pregnancy causes developmental disorders in children.

Pregnant women have regularly used Tylenol (acetaminophen) during pregnancy for decades, believing that it is safe for unborn children. However, following the publication of various studies in recent years, hundreds of lawsuits have been filed by families nationwide, claiming that prenatal exposure to acetaminophen caused unborn children to develop severe ADHD and autism.

Due to common questions of fact and law raised in complaints brought throughout the federal court system, all Tylenol autism and ADHD lawsuits have been centralized before one judge since October 2022, with U.S. District Judge Denise Cote presiding over all coordinated discovery and pretrial proceedings in the Southern District of New York, as part of a federal multidistrict litigation (MDL).

However, throughout the process, Judge Cote has rejected expert witness testimony proposed by plaintiffs, which was needed to clear the cases for trial.

In December 2023, Judge Cote issued an order excluding plaintiffs’ expert witnesses from testifying about Tylenol pregnancy side effects, dismissing about 550 claims. However, a number of plaintiffs who filed claims after that date attempted to press on with just the Tylenol ADHD injury claims, indicating they planned on using different expert witnesses to prove the connection between Tylenol and ADHD.

In March, Judge Cote issued a court order allowing plaintiffs who filed Tylenol ADHD lawsuits after January 12, known as the Mota plaintiffs, to present arguments to the court on whether Dr. Roberta B. Ness could serve as an expert witness to establish causation in those cases.

Defendants objected to the use of Dr. Ness, questioning her experience and the evidence she has used to conclude prenatal exposure to acetaminophen causes ADHD or autism. On July 10, Judge Cote agreed, ruling that Dr. Ness could not speak before juries on Tylenol ADHD and autism causation.

In a move that was anticipated after the ruling, Judge Cote issued an opinion and order (PDF) on August 20, granting summary judgment for all defendants in the litigation and directing the clerk to dismiss all remaining lawsuits pending in the MDL.

“Plaintiffs in this MDL have presented six experts to opine that prenatal exposure to acetaminophen can cause ADHD and/or ASD,” Judge Cote wrote. “The Court carefully considered each expert’s proffered testimony and determined, in two separate opinions, that none of these experts presented reliable testimony on general causation.”

Judge Cote indicated that the dismissal of expert witnesses has left plaintiffs with a piecemeal approach to present causation arguments to juries, which she said was insufficient to justify allowing the claims to move forward.

It is likely that plaintiffs will appeal this latest ruling, as they are appealing the previous summary judgment. However, unless they are able to convince a higher court that the expert witnesses were improperly excluded from testifying, the latest ruling will likely spell the end of Tylenol ADHD and autism lawsuits at the federal level.