Federal judge says research can't be used to link acetaminophen to autism, ADHD

The 440 lawsuits brought against the makers of Tylenol and generic acetaminophen do not have "admissible evidence" to show that prenatal exposure to the medication can lead to autism or ADHD, a federal judge ruled this week.

U.S. District Judge Denise Cote wrote in her opinion that at least one of the experts provided by the plaintiffs "cherry-picked and misrepresented study results and refused to acknowledge the role of genetics in the etiology of either ASD or ADHD."

The ruling is largely consistent with the position of major medical bodies, which say the evidence is not sufficient to make a cause-and-effect link between the use of acetaminophen during pregnancy and issues like autism and ADHD in children.

While there has been some evidence to suggest that acetaminophen use during pregnancy may be linked with neurobehavioral issues, a definitive cause-and-effect has not been established. The risk may be greater with higher doses and more frequent use of the drug, studies note.

A 2021 consensus statement published in Nature Reviews Endocrinology called for more warnings around taking these drugs during pregnancy. But neurobehavioral issues are complex, and other factors during pregnancy, like maternal stress or alcohol use, may play a role in the findings, researchers said.

The statement spurred lawsuits, filed on behalf of families with children with autism and ADHD, which argued that drug manufacturers should have issued warnings to pregnant women about the health risks.

The American College of Obstetricians and Gynecologists (ACOG) maintains that acetaminophen is safe in moderation during pregnancy.

The organization said there is no direct evidence pointing to a relationship between some use of acetaminophen and neurobehavioral issues in children.

"As always, any medication taken during pregnancy should be used only as needed, in moderation, and after the pregnant patient has consulted with their doctor," ACOG said in response to the 2021 consensus statement.

The U.S. Food and Drug Administration said in September that it would not weigh in on the ongoing lawsuits and there is not enough evidence to say acetaminophen causes neurobehavioral issues.

The federal health agency also said that women should talk to their doctors before taking any medications during pregnancy or if they are planning to become pregnant.

A spokesperson for Johnson & Johnson Consumer Inc., the maker of Tylenol and a subsidiary of Kenvue, told ABC News in a statement that the court’s ruling "aligns with the position of the U.S. Food and Drug Administration (FDA) and leading medical organizations that have thoroughly evaluated this matter – the science does not support causation."

The statement continued, "We plan to move to dismiss these lawsuits as there is the potential for unfortunate, real, and long-term public health consequences in allowing scientific guesswork in courtrooms to inform medical decision-making. Healthcare professionals -- not lawyers -- are best positioned to advise their patients on whether taking acetaminophen is appropriate based on their unique medical conditions."

Attorneys for the plaintiff did not immediately reply to ABC News' request for comment.