A federal appeals court on July 13 reinstated expert testimony tying prenatal Tylenol use to autism and attention-deficit/hyperactivity disorder, reviving approximately 550 lawsuits a trial judge had dismissed as built on unreliable science.
Here are five details to know:
1. The ruling is narrow and not about causation.
A three-judge panel of the 2nd U.S. Circuit Court of Appeals vacated the dismissals and sent the cases back to the U.S. District Court for the Southern District of New York. The judges were emphatic about the limits of their decision: “We are not deciding whether there is a general causal relationship between acetaminophen and ADHD and/or ASD,” nor whether manufacturers must warn of any risk.
The appeals court focused on how hard a trial judge may scrutinize a qualified expert who uses accepted methods on a contested scientific question.
Writing for the panel, Circuit Judge Guido Calabresi said in the 64-page decision that the experts used standard methodologies and offered “acceptable interpretations of scientific evidence where scientists may, and in fact do, disagree.”
2. Three experts are back in; two stayed out.
U.S. District Judge Denise Cote had excluded all five general-causation experts in the lead case, Rutledge v. Walgreen. The appeals court panel said Ms. Cote “overstepped [the district court’s] gatekeeping function” by excluding the plaintiffs’ expert testimony, and it sent the case back for further proceedings.
One of the experts now cleared to testify is Andrea Baccarelli, MD, PhD, dean of the Harvard T.H. Chan School of Public Health in Boston, who reported that “substantial evidence” supported a causal link, especially at frequent, high doses. Ms. Cote had ruled that Dr. Baccarelli “cherry-picked and misrepresented study results” and excluded him and other experts.
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 appeals panel said the experts followed methodologies generally accepted in their field. They also affirmed the exclusion of two other experts and declined to rule on a sixth expert in a companion lawsuit.
3. The financial and litigation stakes are considerable.
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 cases were consolidated in 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.
4. Kenvue said the science has not changed.
Summit, N.J.-based Kenvue said the decision addressed only the reliability of expert witnesses, not the underlying facts, and does not “change the fact that credible, independent science shows no proven link between taking acetaminophen and autism or ADHD.”
Numerous studies and a systematic review have found no evidence of such a link. The company also said this ruling did not derail Irving, Texas-based Kimberly-Clark’s $40 billion acquisition of Kenvue, which is expected to close later in 2026.
5. The clinical backdrop.
The revival lands less than a year after the Trump administration linked Tylenol to autism and urged pregnant women to avoid it, unsettling guidance around a drug long considered the preferred analgesic in pregnancy.
Becker’s has reported that Tylenol use among pregnant emergency department patients fell 10% after that announcement, and that Texas has filed lawsuits of its own against the drug’s manufacturers.
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