Updated October 16, 2026: The Second Circuit revived the federal acetaminophen autism and ADHD litigation in July 2026 and denied rehearing on October 16, according to Reuters. Earlier statements that the litigation had effectively ended are no longer current. The appellate rulings do not establish that acetaminophen causes autism or ADHD.
Families bringing Tylenol autism lawsuits allege that prenatal exposure to acetaminophen caused autism or ADHD and that manufacturers and retailers failed to provide adequate warnings. The litigation has focused on how courts evaluate scientific testimony about those claims.
What the lawsuits allege
The cases involve Tylenol and generic acetaminophen products, including store brands sold by major retailers. The families allege that the companies knew or should have known of a potential risk and should have warned pregnant consumers. Those are disputed allegations, not findings of liability.
The federal proceeding concerns ASD and ADHD claims. Other diagnoses should not be presented as established acetaminophen injuries or automatically qualifying conditions. A medication history and diagnosis do not, by themselves, prove causation.
The litigation’s dismissal and revival
The cases were centralized in October 2022 before Judge Denise Cote in the Southern District of New York as MDL No. 3043. An MDL coordinates separate lawsuits for pretrial proceedings; it is not a certified class action.
Judge Cote’s December 18, 2023 ruling excluded plaintiffs’ general-causation testimony, leading to judgments for the defendants. The Second Circuit reversed that outcome on July 13, 2026, finding that three experts had been improperly excluded. It upheld the exclusion of two others and remanded for further proceedings.
The court denied rehearing on October 16, Reuters reported. The revival of about 500 lawsuits does not mean that causation or liability has been established. Our Tylenol litigation overview explains the legal issues and what the rulings mean for the families.
Association and causation in the research
Observational studies can identify patterns that merit investigation, but they must account for other possible explanations. These include genetics, family environment, and the fever, infection, or pain that prompted medication use. Different studies measure exposure and outcomes differently.
The 2019 Boston Birth Cohort study
A 2019 study of 996 mother-child pairs measured acetaminophen biomarkers in umbilical cord blood. Children in the highest exposure group had higher odds of an autism diagnosis than those in the lowest group, with an odds ratio of 3.62. The corresponding ADHD odds ratio was 2.86.
Those figures describe an observed association, not proof that acetaminophen caused the diagnoses. An odds ratio is not the same as a relative risk. Cord-blood measurements also do not establish how much medication a mother took throughout pregnancy or for how long.
Later studies and reviews
A 2024 study covering approximately 2.48 million Swedish children found small associations in conventional analyses, but no association with autism, ADHD, or intellectual disability when comparing siblings. The authors said family-related confounding could explain associations in other models.
A 2026 systematic review and meta-analysis likewise reported no association with those outcomes in analyses restricted to studies at low risk of bias. The findings underscore why an early association should not be reported as an established cause.
The 2021 precautionary statement
A 2021 statement supported by 91 scientists, clinicians, and public-health professionals urged precautionary use and further research. As the Second Circuit explained, the statement represented agreement among its signatories, not a consensus of the entire scientific community, and did not establish a causal relationship.
What federal officials and medical groups have said
In September 2025, President Donald Trump urged pregnant women to avoid Tylenol. The FDA announced a labeling-change process addressing a possible association, while acknowledging that causation remained unestablished.
The American College of Medical Toxicology disputed the causal claim and warned that untreated fever or pain can harm pregnant patients. Kenvue also maintains that the scientific evidence does not establish the alleged link.
Which products contain acetaminophen?
Tylenol and store-brand acetaminophen products contain the drug. Some combination cold, flu, sleep, and pain medicines also contain it, but formulations vary. A brand name alone does not establish the ingredients or whether a product is involved in a particular lawsuit. Check the Drug Facts label and ask a pharmacist if uncertain.
Pregnant patients should discuss treatment with their healthcare professional. Do not assume that switching to another pain reliever is safer or that leaving a fever untreated is harmless.
Editorial correction: This article previously misstated the MDL number as 3403 and described the 2023 ruling as ending the cases. It now reflects the appellate proceedings and distinguishes statistical associations from proven causation.
