New study challenges previous reports linking Tylenol use during pregnancy to autism, ADHD

Multiple studies linking the use of acetaminophen (Tylenol) during pregnancy to neurological disorders like autism and attention deficit hyperactivity disorder (ADHD) are being challenged by a new study that has just emerged from the Karolinska Institute in Sweden and Drexel University.

The study, published in the peer-reviewed medical journal JAMA on Tuesday, analyzed about 2.5 million children born between 1995 and 2019, and found "no evidence of increased risk of autism or ADHD associated with acetaminophen use," according to the study. However, it did find a "marginally increased risk" in models without "sibling controls."

Important to the study was its sibling analysis, conducted to look at full siblings who share both genetic and environmental components. There was no risk found in those observations, which suggests that variables observed in other models may be contributing to skewed data.

“Matched sibling control studies better control for environmental factors that are unknown to the investigators,” Dr. Eric Brenner, an assistant professor of pediatrics at Duke University, said in an email to CNN. Brenner was not involved in the study.

“Sibling controls will most likely grow up in the same home, have similar diets, and will be exposed to similar environments which allows investigators to better control for environmental factors.”

'Admissible evidence': federal judge rules against 440 Tylenol lawsuits

A federal judge ruled that 440 lawsuits against Tylenol makers do not have "admissible evidence" showing a link between prenatal use of Tylenol and autism or ADHD, according to reporting by ABC News.

U.S. District Judge Denise Cote wrote in her opinion that the presentations of some experts seemed to be "cherry-picked and misrepresented study results." The judge acknowledged that at least one expert "refused to acknowledge the role of genetics in the etiology of either ASD or ADHD."

The strength of the recent study published in JAMA is its duration and number of participants. The results that show no real risk of acetaminophen use during pregnancy as a contributing factor to autism and ADHD are in agreement with the American College of Obstetricians and Gynecologists, which maintains the painkiller is safe for pregnant women to use.

A committee of the Society for Maternal-Fetal Medicine, a 5,000-member nonprofit, determined in 2017 that "the weight of evidence is inconclusive," USA TODAY previously reported.

The U.S. Food and Drug Administration has chosen to not weigh in on the ongoing lawsuits. The FDA publicly commented on the issue in 2015 when it stated it was investigating concerns. After reviewing studies, the FDA noted "potential limitations" and maintained its stance that Tylenol for pain in pregnancy is safe at this time.

Contributing: Karen Weintraub

This article originally appeared on USA TODAY: Is prenatal Tylenol use linked to autism and ADHD? New study says no