12/4/2025
Update on the Tylenol MDL
In the wake of a September 22 briefing by President Trump during which he discouraged pregnant patients from taking Tylenol and implied a causal association between the drug if taken during pregnancy and autism, the drug’s manufacturer Kenvue (a Johnson and Johnson [J&J] spinoff) urged the U.S. Food and Drug Administration (FDA) to refrain from adding a warning label about the risk.
The manufacturer pointed to the FDA’s own review of the developing science surrounding any risks in taking Tylenol (generically known as acetaminophen) after which the agency repeatedly declined to establish a causal link between the drug and the development of autism. In an October 17 statement, Kenvue wrote:
Consistent with the body of evidence, numerous leading professional organizations— including the American Academy of Pediatrics, the American College of Obstetricians and Gynecologists, the American Psychiatric Association, and the Society for Maternal-Fetal Medicine—have independently reviewed the science and concluded that there is no causal association between acetaminophen use during pregnancy and neurodevelopmental disorders.
The company further argues that “because the science does not support a change to the warning language and the proposed labeling changes could be harmful to pregnant women and result in adverse pregnancy outcomes, Kenvue strongly opposes the changes and believes that the existing instruction to speak to a health professional before use in pregnancy is the most conservative and appropriate labeling. “
On the same day as the administration’s statements, the FDA Commissioner issued two public statements on the current science of Tylenol use during pregnancy and acknowledged no such link to autism. However, in contrast, the FDA later announced that it would propose new labeling that stated there was some evidence that Tylenol and acetaminophen “may be associated” with an increased risk of autism spectrum disorder and attention deficit hyperactivity disorder.
Kenvue’s statement was made in the wake of the FDA’s receipt of a citizen petition filed by the Informed Consent Action Network who requested that a warning be added to the drug that notes a causal link between the use of acetaminophen and the risk of neurodevelopmental disorders. The group is also asking that the labeling for professionals be revised to describe the link. The company responded by stating
“The Citizen Petition does not explain why the two proposed warnings describe significantly different degrees of scientific certainty or why a revision to professional labeling is proposed for acetaminophen products, which do not have professional labeling. In addition, the Citizen Petition conflates two distinct neurological conditions, ASD and ADHD, treating them as one despite the clear differences between the two that would necessitate independent scientific evidence and analyses. Findings drawn for one neurological condition should not be automatically applied to the other condition without rigorous studies specific to each.”
Despite Kenvue’s position and the FDA Commissioner’s statements subsequent to the filing of the citizens petition, the Texas Attorney General’s Office sued J&J and Kenvue, accusing the companies of engaging in deceptive trade practices by claiming the drug was safe for pregnant women and their children and hiding the known risks.
The issue of any link between acetaminophen and autism has been the subject of an MDL filed in 2022. That litigation had stalled in 2023 after the judge presiding over the MDL, U.S. District Judge Denise Cote for the Southern District of New York, rejected every one of the plaintiffs’ expert witnesses, stating that the methodologies used were flawed and the research had been cherry-picked which made their expert opinions unreliable.
That decision was appealed to the Second Circuit and may be energized by the current statement by the Trump administration. On November 17, members of a three-judge panel of the 2nd U.S. Circuit Court of Appeals appeared to question U.S. District Judge Denise Cote’s earlier order barring the plaintiffs’ witnesses, in particular, Andrea Baccarelli, dean of the Harvard T.H. Chan School of Public Health, acknowledging that although judges serve in a gatekeeping role when evaluating experts, they cannot bar testimony simply because they disagree with the conclusions. The panel emphasized that the role of the court is to ensure an expert’s methodology is sound. Counsel for drug manufacturer Kenvue defended Judge Cote’s decision, arguing that “no scientist or regulator has ever concluded that acetaminophen causes ADHD.”
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After several months of rulings on the insufficiency of the expert testimony being offered to support plaintiffs’ claims that in utero exposure to the popular pain killer, Tylenol (generic acetaminophen), was linked to developmental disorders including ASD (autism spectrum disorder) and ADHD (attention-deficit/ hyperactivity disorder), on August 20, 2024, the presiding judge granted the defendants’ motion for summary judgment and dismissed all cases currently pending in the MDL.
The recent decision was the culmination of an extended process in which the plaintiffs sought to prove that the scientific evidence and methodologies being offered by experts to support their claims were credible, starting with the first Daubert hearing that was held on December 7, 2023. At that hearing, counsel for each side presented arguments supporting their respective positions; the five experts – an epidemiologist, a toxicologist, a teratologist, a pharmacologist and a psychiatrist – did not testify. In addition to other concerns, Judge Denise Cote of the U.S. District Court for the Southern District of New York also observed that a single transdiagnostic analysis was used to support the plaintiffs’ contention that prenatal exposure to Tylenol could lead to an increased risk of both ASD and ADHD, which are two separate and distinct neurodevelopmental disorders (NDDs).
In a 148-page opinion issued on December 19, Judge Cote ruled that there is no scientific consensus that acetaminophen causes either ASD or ADHD, citing the U.S Food and Drug Administration and other groups currently conducting research concluding:
“….there is no generally accepted scientific conclusion that in utero exposure to acetaminophen causes either ASD or ADHD” and “ the plaintiffs’ experts have not reliably opined so either.”
As a result, the judge barred the five expert witnesses and dismissed the cases in the MDL; the dismissals were expected to lead to an increase in cases filed in state courts around the country. She also requested that the parties submit a joint letter by January 12, 2024 outlining next steps in the litigation; she also noted, however, that her ruling had left the plaintiffs with no admissible evidence.
In an unexpected turn, in February, 2024, a separate group of plaintiffs that were not part of the group of cases already filed and dismissed in December petitioned Judge Cote to have their expert, Dr. Roberta Ness, heard on the issues of Tylenol use and subsequent diagnoses of ASD and ADHD. Judge Cote granted the request and agreed to consider the deposition testimony of Dr. Ness. The defendants filed a motion to exclude Dr. Ness’ testimony on June 11.
On July 10, the Judge issued an 84-page opinion granting the defendants’ motion for summary judgment and excluding Dr. Ness’ testimony on the basis that the plaintiffs failed to ensure that the scientific evidence they presented was not only relevant but reliable.
In response to her subsequent request to the plaintiffs that they explain why she should not enter final judgment in favor of the defendants, the plaintiffs responded with the argument that they could use statements by one of the defendant’s expert witness, Dr. Stephen Faraone to provide the missing admissible evidence. However, the Judge again ruled against the plaintiffs stating:
“No reasonable jury could find, from the smattering of Dr. Faraone’s past statements and isolated pieces of his deposition identified by plaintiffs that prenatal exposure to acetaminophen can cause ADHD in offspring. As such, Plaintiffs have failed to make a sufficient showing on an essential element of their case with respect to which they have the burden of proof. Summary judgement is therefore granted for the defendants.”
The August 20 order enters final judgment for the defendants in all pending cases and effectively ends this litigation in the federal court.
Resources
https://www.law360.com/articles/1872153/judge-rules-lack-of-expert-dooms-families-tylenol-mdl
