Study Raises Doubts About Link Between Tylenol and Autism in Children

Findings come as lawyers attempt to resurrect hundreds of Tylenol autism lawsuits, which were dismissed last year by a federal judge.

Amid continuing public debate and litigation over whether Tylenol’s active ingredient, acetaminophen, may cause autism or attention deficit hyperactivity disorder (ADHD) among children exposed to the drug before birth, a new study indicates that much of the existing research has suggested a possible association between prenatal use and developmental disorders.

However, according to the findings published in The BMJ on November 10, the problem is that most of the researchers who conducted or reviewed those studies rated the evidence as low quality and questioned how reliable the conclusions may be.

Tylenol (acetaminophen) has been widely used during pregnancy for decades, largely because it has long been considered safe for unborn children. However, in recent years, several studies have reported associations between prenatal acetaminophen exposure and an increased risk of certain developmental disorders.

Questions about the connection were again sparked in September, when the U.S. Food and Drug Administration (FDA) announced it was requiring new label warnings for Tylenol and other acetaminophen-containing products. Health officials indicate that pregnant women should now be warned to use the drug with caution, and only when necessary. However, they have stopping short of recommending that women avoid Tylenol during pregnancy altogether.

In the new study, a group of researchers from the University of Liverpool say the current data is inconclusive, after looking at nine reviews involving 40 different studies and performing a meta analysis.

The researchers determined that the “reviews reported a possible strong association between maternal paracetamol (the European name for acetaminophen) intake and autism or ADHD or both in offspring.” However, seven of the nine reviews done on the studies warned of potential bias and confounding factors that may be at play in the conclusions, the researchers noted.

Out of the nine reviews of the 40 studies, two determined confidence in the findings was low, while the other seven reviews judged confidence in the findings as critically low. The researchers noted that their own analysis of their confidence in the findings was also low to critically low.

The research team concluded that pregnant women, doctors, regulatory bodies and people with autism and ADHD should be told about the low quality in the evidence that Tylenol causes autism or ADHD. They also called for higher quality studies that would control for familial and unmeasured confounders to help improve the evidence and deliver a clearer picture on the potential link.

Tylenol Autism and ADHD Lawsuits

For years, drug makers have faced a growing number of Tylenol autism and ADHD lawsuits in federal courts nationwide, citing studies associating acetaminophen use with neurodevelopmental disorders.

These lawsuits were assigned to U.S. District Judge Denise Cote in the Southern District of New York in October 2022. However, in December 2023, Judge Cote issued a sweeping order excluding all of the plaintiffs’ expert witnesses under the federal Daubert standard, determining that the scientific methods used to link acetaminophen to autism were not reliable enough to present to a jury. This led to the entire MDL being dismissed before any bellwether trials could take place.

Plaintiffs are currently pursuing an appeal in the Second Circuit Court of Appeals, arguing that the FDA’s new label requirements indicate that the science is good enough to require a warning from the nation’s leading drug regulatory agency, so it should also be good enough for the courts. It is unclear when the appeals court will issue an opinion.

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