Court revives 550 Tylenol autism lawsuits, but not causation

A federal appeals court on July 13 revived expert testimony in about 550 lawsuits alleging a link between prenatal Tylenol use and autism or attention-deficit/hyperactivity disorder. The decision sent the cases back to the U.S. District Court for the Southern District of New York after a trial judge had dismissed them as relying on unreliable science.

The ruling does not decide whether acetaminophen causes autism or ADHD. The 2nd U.S. Circuit Court of Appeals said it was not addressing whether there is a general causal relationship between acetaminophen and ADHD and/or ASD, or whether manufacturers must warn consumers about any risk. Instead, the panel focused on how a trial judge may evaluate expert testimony in a contested scientific dispute.

Writing for the court, Circuit Judge Guido Calabresi said in the 64-page opinion that the experts used standard methods and offered acceptable interpretations of scientific evidence in an area where scientists may disagree. The panel said the district court went too far in excluding the plaintiffs’ expert testimony and overstepped its gatekeeping role.

The litigation is centered on Rutledge v. Walgreen, the lead case in the multidistrict proceeding. U.S. District Judge Denise Cote had excluded all five general-causation experts in that case. The appeals court vacated those dismissals and sent the case back for further proceedings.

Three of those experts were cleared to testify again. One is Andrea Baccarelli, MD, PhD, dean of the Harvard T.H. Chan School of Public Health in Boston. He reported that substantial evidence supported a causal link, especially with frequent, high doses. Judge Cote had previously said Dr. Baccarelli cherry-picked and misrepresented study results.

The panel also approved Eric Hollander, MD, a psychiatrist and director of the autism and obsessive compulsive spectrum program at New York City’s Albert Einstein College of Medicine, and Brandon Pearson, PhD, a toxicologist and assistant professor of environmental health services at Columbia University in New York City. The court said they followed methodologies generally accepted in their fields.

The panel left out two other experts and declined to rule on a sixth expert in a companion lawsuit. The source did not provide additional details about those experts beyond their exclusion or the separate ruling.

The financial stakes are significant. The defendants are Kenvue, the Tylenol maker spun off from Johnson & Johnson in 2023, and major retailers that sell generic acetaminophen, including Walmart, CVS, Walgreens, Costco, Target and Kroger. The revived lawsuits are part of a multidistrict litigation covering roughly 550 claims.

Bloomberg estimated in March that Kenvue could face thousands of additional lawsuits and billions of dollars in potential settlements. The source did not report any new estimate from the court itself, and it did not say whether any settlement talks are underway.

Kenvue said the ruling did not change the underlying science. The Summit, N.J.-based company said the decision dealt only with the reliability of expert witnesses and not the facts at issue. It also said the ruling does not change the fact that credible, independent science shows no proven link between taking acetaminophen and autism or ADHD.

The company pointed to numerous studies and a systematic review that it said found no evidence of such a link. The source did not identify those studies individually. Kenvue also said the appellate ruling did not disrupt Irving, Texas-based Kimberly-Clark’s $40 billion acquisition of the company, which is expected to close later in 2026.

The broader backdrop has added attention to the lawsuits. Less than a year before the appellate ruling, the Trump administration linked Tylenol to autism and urged pregnant women to avoid it. That announcement unsettled guidance around a drug long considered the preferred analgesic in pregnancy.

Becker’s previously reported that Tylenol use among pregnant emergency department patients fell 10% after that announcement. The outlet also reported that Texas has filed lawsuits of its own against the drug’s manufacturers. Those reports were cited as part of the clinical and legal context around the federal cases.

The 2nd Circuit’s decision may shape how similar expert testimony is treated in future disputes, but the court was careful to describe its ruling as narrow. It did not decide whether acetaminophen causes autism or ADHD, and it did not rule on whether any manufacturer had a duty to warn about such a risk.

For now, the main effect is procedural: the dismissed claims are back in play, the expert testimony can be heard again, and the multidistrict litigation will continue in the Southern District of New York. The source did not report a new trial date or any next step beyond further proceedings in that court.

The appeals court’s analysis turned on the limits of judicial gatekeeping under the standards for expert evidence. According to the panel, the plaintiffs’ experts relied on accepted methods even though the underlying science remains contested. The court said that disagreement among scientists does not by itself make an expert opinion inadmissible.

That distinction matters because the lawsuits rest on scientific evidence that the trial court had found too unreliable to reach a jury. The appellate ruling reopened the door to those claims, but it left the underlying causation question unresolved. As a result, the litigation now returns to the trial court with the expert testimony restored and the core scientific dispute still unsettled.

The source did not report any further response from the plaintiffs, any additional comment from the retailers named in the litigation, or any immediate change in consumer guidance. It also did not say whether the revived cases will be grouped with any other pending acetaminophen-related claims beyond the multidistrict proceeding already described.

In short, the appellate court revived the lawsuits and the expert evidence behind them, but it stopped short of saying Tylenol causes autism or ADHD. That question remains open as the cases move back to district court.