Tylenol use in pregnancy linked to ADHD, study shows

While pregnant women are routinely told by physicians to avoid most over-the-counter medications, acetaminophen has generally been considered safe.

But now, new research is posing some questions about the presumed safety of acetaminophen use during pregnancy.

The study, published in the journal JAMA Pediatrics, found that women who took the drug during pregnancy were approximately 40 per cent more likely to have children diagnosed with attention deficit hyperactivity disorder than mothers who took none.

Also see: New warnings on U.S. Tylenol bottles -- should Canada do the same?

Researchers followed 64,000 Danish mothers and children from a variety of socioeconomic backgrounds between 1996 and 2002.

“[The results] are worrisome because more than 50 per cent of the women took acetaminophen; it’s an over-the-counter drug and they can freely buy, and use it at their discretion,” Dr. Beate Ritz, co-author and chair at UCLA, tells Time. “It’s considered relatively safe, and maybe it’s not.”

The researchers determined the frequency of acetaminophen use during pregnancy and later assessed the children's behaviour at age seven using parent questionnaires. They also looked at diagnoses and prescriptions for ADHD medication among the children.

Also see: The shocking truth about ADHD in children

The results showed that mothers who used the pain reliever for headaches or to reduce fevers saw a 37 per cent greater risk in their kids receiving an ADHD diagnosis. The mothers also had a 29 per cent greater risk that their kids would needed ADHD medication.

“When women reported having used acetaminophen for 20 or more weeks during pregnancy, the risk for HKD diagnosis in children almost doubled,” the authors write. HKD is a severe form of ADHD.

While the study may be worrisome to pregnant mothers, physicians note that the findings are preliminary and that further research is needed, reports the Toronto Star.

The study does not prove a cause-and-effect relationship between acetaminophen and ADHD in children.