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Using acetaminophen such as Tylenol in pregnancy linked to higher rates of ADHD, autism

Experts caution that it is too soon to tell pregnant women not to use the over-the-counter painkiller, better known as Tylenol.

Tylenol Extra Strenth is shown in a medicine cabinet.
Tylenol Extra Strenth is shown in a medicine cabinet.Read moreAP

Exposure to acetaminophen in the womb may have some connection with a child’s risk for attention deficit/hyperactivity disorder (ADHD) and autism spectrum disorder, suggests a new study published Wednesday in JAMA-Psychiatry.

But experts caution that it is too soon to tell pregnant women not to use the over-the-counter painkiller, better known as Tylenol.

The study, conducted by researchers with the Johns Hopkins University Bloomberg School of Public Health and funded by the National Institutes of Health, does not prove a causal relationship between the common over-the-counter pain medication and the disorders.

The authors and other experts said more research is warranted to determine if there is a connection between the medicine and the conditions.

“In the past, acetaminophen use during pregnancy was considered to be safe,” said study author Xiaobin Wang, a Johns Hopkins pediatrics professor. “Our findings along with previous studies raise the concern about potential risk of acetaminophen use during pregnancy. This information helps the women and their providers to weigh the risk and benefit of acetaminophen use during pregnancy and make informed decisions.”

Unlike much of past research that relied on women self-reporting acetaminophen use during pregnancy, the new findings are based on acetaminophen levels detected in actual umbilical cord blood samples of 996 births. Researchers used data from the Boston Birth Cohort, a long-term study of factors influencing pregnancy and child development.

The researchers classified the amount of acetaminophen and its byproducts in the samples into thirds, and found that the highest third of exposure was associated with nearly three times the risk for ADHD, and more than three times the risk for autism spectrum disorder.

Still, the new study comes with notable caveats, other experts say. It is an observational study — meaning researchers draw inferences from observing a sample of people — not a randomized trial with a control group that could tease out cause and effect.

It can’t account for other factors such as genetics, family history, or environmental factors beyond the acetaminophen.

» READ MORE: Autism in girls often isn't diagnosed for a surprising reason.

In addition, the nearly 1,000 children whose data are in the study represent a higher-risk population than the general public. The Boston Birth Cohort includes a significant proportion of lower-income single mothers, and the babies were more likely to have been born preterm or low birthweight — known risk factors for developmental disabilities.

“The sample is not a general population sample,” said Joseph McCleery, an autism researcher and assistant professor of psychology with St. Joseph’s University’s Kinney Center for Autism Education and Support. Especially in autism, environmental factors are generally not as important as genetic factors, he said.

» READ MORE: One in three kids with ADHD get no support services

Still, McCleery, who was not involved in the research, said the new findings are provocative.

“There’s a lot more work to be done here, but they show a solid relationship of likely perinatal use of acetaminophen and higher risk” of ADHD and autism, McCleery said.

“I would say this is more convincing than previous research that there is a connection between acetaminophen and autism,” he said. “It suggests we should be thinking about this more as a possible causal risk factor.”