On July 13, 2026, a Second Circuit panel revived more than 500 lawsuits alleging that prenatal Tylenol use causes autism and ADHD. The ruling reversed the decision that had ended the litigation and returned Kenvue, the Johnson & Johnson consumer-health spinoff that makes Tylenol, to active MDL defense. For background on the underlying product claims, related Tylenol litigation coverage explains the warning theory.
This analysis covers the MDL background, Daubert rulings, appellate outcome, Rule 702 implications, and remand strategy for plaintiff and defense counsel.
The Formation of MDL 3043 and Its Defendant Structure
The Judicial Panel on Multidistrict Litigation consolidated the litigation on October 5, 2022, in In re Acetaminophen ASD/ADHD Prods. Liab. Litig., 637 F. Supp. 3d 1372 (J.P.M.L. 2022), MDL No. 3043, No. 1:22-md-03043 (DLC) (S.D.N.Y.). The order moved eighteen actions from seven districts to the Southern District of New York before Judge Denise L. Cote and cited common questions over "whether prenatal exposure to acetaminophen can cause ASD and ADHD."
The defendant structure separates the branded manufacturer from the retailer label-holders. Kenvue Inc., spun off from J&J's consumer-health unit, is the operative branded-manufacturer defendant. The model short-form complaint order names fourteen retailer defendants, including CVS, Kroger, Target, Walgreens, and Walmart, that sold store-branded generic acetaminophen made by others. Plaintiffs alleged these retailers "failed to warn pregnant women that prenatal APAP exposure is associated with and causes the neurodevelopmental harms of ASD and/or ADHD." The coordinated-case structure in MDL 3043 mirrors the procedural frameworks used in other pharmaceutical mass tort litigation involving defective medical products.
The pleaded counts are strict liability for failure to warn, strict liability for design defect due to inadequate warnings, negligence, and negligent misrepresentation, with an apparent-manufacturer count against retailers. At the time of the December 2023 exclusion, the MDL held approximately 550 cases.
Judge Cote's December 2023 Daubert Exclusions
Judge Cote issued a 148-page opinion on December 18, 2023, that excluded all five plaintiffs' general causation experts: Dr. Andrea Baccarelli, Dr. Brandon Pearson, Dr. Robert Cabrera, Dr. Stan Louie, and Dr. Eric Hollander. She applied the amended Rule 702 standard that took effect December 1, 2023, which requires the proponent to show "that it is more likely than not that . . . the expert's opinion reflects a reliable application of the principles and methods to the facts of the case."
Several reliability defects cut across all five experts. Each used a "transdiagnostic" analysis that folded ASD, ADHD, and other neurodevelopmental disorders into one causation opinion, which the court held obscured limitations in the scientific literature and allowed a results-driven reading of inconsistent data. The court treated failure to address confounding as a reliability defect, singling out confounding by indication and genetic confounding as the primary unaddressed variables.
The court's expert-specific findings tracked those themes:
- Baccarelli: a "cursory" Bradford Hill analysis that cited other research rather than conducting his own and failed to address contrary meta-analyses.
- Pearson: "result-driven analysis" that downplayed studies undercutting his causation thesis and ignored author cautions about familial confounding.
- Hollander: an opinion supporting the transdiagnostic approach, which the court treated as inadequately justified. That cross-cutting defect was his primary exclusion ground.
- Cabrera: animal studies that "do not assess whether acetaminophen causes ADHD/ASD in humans."
- Louie: excluded with the rest. The exclusions left "no admissible evidence for general causation."
With no admissible causation evidence, the litigation collapsed. Following an order-to-show-cause process, final judgment was entered in approximately 550 cases. Judge Cote separately rejected the plaintiffs' last ADHD expert in July 2024, and plaintiffs appealed.
The Second Circuit's July 13, 2026 Holding
The panel of Judges Guido Calabresi, Gerard E. Lynch, and Eunice C. Lee split the ruling expert by expert in Rutledge v. Walgreen Co. (2026), Nos. 24-916-cv(L), 24-1121(Con), 24-2360(Con), 24-2594-cv (2d Cir. July 13, 2026). It vacated the exclusions of Baccarelli, Hollander, and Pearson, holding that "the District Court exceeded its discretion by excluding" their testimony. It affirmed the exclusions of Cabrera and Louie, and directed reconsideration of a sixth expert, Dr. Ness, in a related sub-case.
The reasoning turned on the boundary between screening methodology and grading conclusions. Judge Calabresi wrote that the district court "went beyond its proper role as gatekeeper by excluding experts whose testimony was consistent with the methodologies actually employed in their field; by substituting its own understanding of various epidemiological criteria for that of the expert scientists; and by faulting the scientists for reaching particular conclusions where there is disagreement in the scientific community." The governing rule the panel stated: "When an expert reliably applies a scientifically accepted methodology on an issue that is reasonably subject to debate, it is for the jury to decide the opinion's correctness."
On Baccarelli, the panel found the district court penalized him "for using a methodology that epidemiologists routinely use," and faulted the court for demanding certainty about the biological mechanism when Bradford Hill asks only whether a hypothesized causal link is credible in light of current science.
The panel drew a clear line on the two affirmed exclusions. Cabrera's opinion "did not weigh or properly synthesize the factors under the so-called Bradford Hill methodology that he employed." Louie "failed to explain how he extrapolated from the studies he analyzed to reach his final conclusion." The panel also affirmed the district court's rejection of defendants' federal preemption defense. And it made its limits explicit: "We are not deciding whether there is a general causal relationship between acetaminophen and ADHD and/or ASD."
The Procedural Meaning of the Remand
Remand returns the roughly 550 cases to Judge Cote, where the parties will litigate renewed Rule 702 challenges to the three reinstated experts before any verdict path opens. The panel invited that process and noted the district court "may consider it prudent to invite the parties and their experts to address those new studies," a reference to post-2023 literature.
Kenvue signaled its strategy in a July 13, 2026 statement. The company said it would renew its challenge to plaintiffs' expert reliability, maintained that credible, independent science shows no proven link, and said it was exploring all options. Kenvue and the retailer defendants sought an extra 45 days to prepare a rehearing petition because appellate counsel had retired.
Kenvue's financial disclosures have not moved with the litigation. Its Form 10-Q for the quarter ended March 29, 2026 repeats that the company "is unable to reasonably estimate either the likelihood or the magnitude of its potential liability," language that has held across fiscal 2023, fiscal 2024, and fiscal 2025 annual filings. No verdict or settlement figure exists in the MDL, and the reinstated experts must survive fresh Daubert analysis before any bellwether schedule is set.
The Ruling's Effect on Rule 702 Gatekeeping
After the December 2023 amendments to Rule 702, this appellate decision qualified the exclusionary trend at the appellate level. Those amendments, per the Advisory Committee Notes, told courts to treat the sufficiency of an expert's basis and methodology application as admissibility questions under a preponderance standard and to remove those questions from jury-weight treatment.
The acetaminophen decision draws a narrower line without disturbing the standard. Courts may scrutinize whether a generally accepted methodology was reliably applied. They may not substitute their own view of which scientific conclusions are correct in a genuinely contested field.
The current causation record remains sharply divided. Plaintiffs must defend how their experts synthesize the broader epidemiology and address confounding, while defendants point to the Ahlqvist (2024) nationwide sibling-control study of nearly 2.5 million children, which found an autism hazard ratio of 0.98 after sibling control. The FDA initiated a label-change process on September 22, 2025, while stating that "a causal relationship has not been established." ACOG's September 2025 Practice Advisory kept acetaminophen in first-line pregnancy analgesic and antipyretic guidance.
Practitioner Takeaways for Plaintiff and Defense Counsel
The split holds hands each side concrete instructions for the next round. Its reasoning gives plaintiffs a route back into the MDL and gives defendants appellate language for renewed exclusions.
For plaintiff counsel:
- Anchor every methodological choice to field-standard practice documented in peer-reviewed literature, and engage confounding by indication and genetic confounding affirmatively so each Bradford Hill weighting and multi-outcome framework has precedent beyond the expert's own say-so. The reversal does not cure silence on study-author cautions.
- Address adverse studies directly, especially the Ahlqvist sibling-control study in JAMA and the 2025 BMJ umbrella review, because cherry-picking remains a live vulnerability and Cabrera's affirmed exclusion shows that invoking Bradford Hill without synthesis fails.
For defense counsel: Use the affirmed exclusions of Cabrera and Louie as appellate-blessed authority for renewed Rule 702 challenges based on failed Bradford Hill synthesis and unexplained extrapolation. Frame the reversal as narrow because it validated a routinely used epidemiological method without endorsing general causation, and preserve the panel's scope disclaimers as a trial asset.
Both parts should treat the September 2025 FDA labeling review as context. It may support the "knew or should have known" element in failure-to-warn claims, and its own disclaimer forecloses using it as causation evidence. Practitioners tracking manufacturer-defendant records across product liability MDLs will find a useful comparison in the talc litigation analysis of J&J-related exposure.
What the Remand Means for Litigation Strategy
The remand restores litigation pressure without creating settlement value on its own; that value now turns on the next Rule 702 record. No verdict, bellwether schedule, or shift in Kenvue's inability-to-estimate language will arrive until the three reinstated experts clear fresh Daubert review, so the filings to watch are the supplemental expert record and Kenvue's next SEC disclosures.
For additional causation-record strategy in complex exposure MDLs where confounding challenges dominate, see the related Paraquat analysis.
