Judge Excludes Expert Witnesses Linking Prenatal Tylenol Exposure to Autism and ADHD

In a decision that will prevent families from moving forward with Tylenol autism and ADHD lawsuits in the federal court system, the U.S. District Judge presiding over the litigation has determined that expert witnesses will not be allowed to testify that prenatal exposure to acetaminophen causes autism and attention deficit hyperactivity disorder (ADHD) in children.

Tylenol (acetaminophen) has been widely used by pregnant women for decades, largely due to the widespread belief that it is safe for unborn children. However, a growing number of lawsuits have been filed in recent months by families nationwide, each raising similar allegations that drug makers failed to adequately warn pregnant women about the growing evidence that in utero Tylenol prenatal exposure may cause autism or ADHD.

Given common questions of fact and law over the adequacy of the Tylenol pregnancy warnings, the U.S. Judicial Panel on Multidistrict Litigation (JPML) established coordinated pretrial proceedings last year, centralizing all claims brought throughout the federal court system before U.S. District Judge Denise Cote in the Southern District of New York, as part of a federal multidistrict litigation (MDL).

As part of the coordinated pretrial proceedings, Judge Cote determined early in the litigation that the Court would prioritize discovery into the link between Tylenol and autism, as well as ADHD and other developmental problems. This resulted in a series of hearings earlier this month, to test the admissibility of plaintiffs’ expert witness testimony, which would establish a causal link between Tylenol use during pregnancy and the two developmental disorders.

Tylenol Plaintiffs’ Expert Witnesses Rejected

In September, the manufacturers of Tylenol and generic acetaminophen products filed a motion seeking to exclude five expert witnesses proposed by the plaintiffs on general causation, arguing that the experts relied on speculative science to determine that Tylenol causes autism. The defendants maintain that there remains are very limited medical and scientific literature to support the opinions expressed, and that the plaintiffs’ experts ignored better-conducted studies that contradict their findings.

Following the hearings, Judge Cote issued an opinion (PDF) on December 18, granting defendants’ motion to exclude the five plaintiffs’ expert witnesses from testifying, after determining that the scientific approaches and studies used were not sound enough to allow the opinions to be presented to a jury.

“With these rulings, the plaintiffs do not have admissible evidence to demonstrate that prenatal exposure to acetaminophen causes either ASD or ADHD in offspring,” Judge Cote determined in the ruling, which will likely result in the dismissal of all claims pending in the federal court system, unless the decision can be reversed on appeal.

In an order (PDF) issued on the same day, Judge Cote called on the parties to meet and confer on the next steps for the litigation and submit a joint status letter by January 12, 2024.