Acetaminophen is an active ingredient in medicines such as Tylenol and Excedrin. It is also the most commonly used over-the-counter pain and fever reliever among pregnant women.
Now, a new research is suggesting that it may also boost the risk of attention deficit hyperactivity disorder (ADHD) in children.
The research, published in JAMA Pediatrics on Monday, is still preliminary. However, it is raising questions over whether the drug should be used during pregnancy.
"It is important we follow up [on] the potential health-risks that acetaminophen may cause," Zeyan Liew, candidate with the UCLA Fielding School of Public Health and an author of the study, told The Huffington Post. "ADHD incidence has been noticed to be increased in the last decades, and we are interested in searching for avoidable environmental factors that may contribute to the trend."
In reaching their conclusion, the researchers used the Danish National Birth Cohort to study pregnancy complications and diseases in children. They focused particularly on medications and infections.
The researchers examined 64,322 children and mothers enrolled in the Danish Cohort from 1996 to 2002. Following up with parents once their children reached the age of seven, the researchers asked questions about behavioral problems. They also obtained diagnoses of hyperkinetic disorder and identified if ADHD medications, mostly Ritalin, were used by the children.
Over half of the mothers reported using acetaminophen during their pregnancy. The researchers found that children whose mothers used acetaminophen while pregnant, had a 13 to 37 percent higher risk of being diagnosed with hyperkinetic disorder, being treated with ADHD medications or ADHD-like symptoms at the age of seven. Furthermore, there were stronger associations with those who took acetaminophen longer into their pregnancy.
"It's known from animal data that acetaminophen is a hormone disruptor, and abnormal hormone exposures in pregnancy may influence fetal brain development," said Dr. Beate Ritz, professor and chair of the department of the Fielding School and one of the paper's senior authors.
Ritz said that acetaminophen can cross the placental barrier, possibly interrupting fetal brain development through interference with maternal hormones or through neurotoxicity.
"We need further research to verify these findings, but if these results reflect casual associations, then acetaminophen should no longer be considered a 'safe' drug for use in pregnancy," said Dr. Jorn Olson, co-author of the paper.
ADHD is one of the most common brain disorders among children. It is often characterized by impulsivity, hyperactivity and inability to stay focused. Though its exact causes are unknown, experts point to a combination of genetic and non-genetic factors.
