ADHD News & Research

Study: Acetaminophen Use During Pregnancy May Increase Risk of ADHD in Children

A large national study links mothers’ repetitive use of a common pain reliever to an increased likelihood of ADHD in their children.

October 31, 2017

A large study has found a correlation between acetaminophen use during pregnancy and an increased risk of ADHD in children. Though the study establishes no direct causation, its results may discourage pregnant women from taking acetaminophen — sold in the U.S. under the brand name Tylenol, among others — to manage their pain.

The study examined almost 113,000 Norwegian children, 2,246 of whom had been diagnosed with ADHD, along with their biological mothers. The subjects were participants in the Norwegian Mother and Child Cohort Study, a large nationwide study conducted by the Norwegian Institute of Public Health. Of the mothers examined, 27 percent had used acetaminophen in one trimester of their pregnancy; 16 percent had used it in two, and 3.3 percent had taken it in all three.

The children of mothers who had taken the drug for more than 7 days total during their pregnancy had a slightly increased risk of having ADHD, compared to those who took no acetaminophen. Taking acetaminophen for more than 29 days nearly doubled the risk of ADHD in the children studied. These results occurred even after researchers controlled for potentially mitigating factors, including the parents’ own ADHD symptoms and the rate of acetaminophen use before pregnancy.

The researchers hypothesized that hormonal changes sparked by acetaminophen use could impact a baby’s development, or that the ADHD link may be related to oxidative stress caused by the medication. There may also be a link between paternal use of acetaminophen and ADHD, they said, but that particular relationship was not explored in this research.

The lead author of the study, Eivind Ystrøm, emphasized that pregnant women don’t need to avoid Tylenol completely when they’re in pain. Instead, those who require “continuous acetaminophen for a longer period” should consult with a doctor, he said in an email to CNN.

The study1 was published online in Pediatrics in late October.

Editors Note: A similar study, published in April of 2018, reached much the same conclusions as the one above, but also found an increased risk of autism linked to acetaminophen use during pregnancy. More about that study, conducted by the Hebrew University of Jerusalem, can be found in the American Journal of Epidemiology.

1 Ystrom, Eivind, et al. “Prenatal Exposure to Acetaminophen and Risk of ADHD.” Pediatrics, vol. 140, no. 5, 2017, doi:10.1542/peds.2016-3840.