The study does not show that prenatal exposure to
the medication causes ADHD, and the increase in risk is small, Dr.
Jorn Olsen, one of the study's authors, told Reuters Health.
Nevertheless, "it's reasonable to say that there's no reason to use
these drugs during pregnancy unless there is a clear medical
indication," said Olsen, a professor of epidemiology at UCLA and at
Aarhus University in Denmark.
Acetaminophen, or paracetamol, has been available over the counter
since the 1950s, Olsen and his colleagues note in their report in
While the medication is widely considered to be safe to use during
pregnancy, they add, recent studies have shown it can disrupt
hormone function in pregnant rats and mice.
Given that hormones play a key role in guiding fetal development,
the researchers decided to investigate whether acetaminophen
exposure might be related to ADHD risk. They looked at 64,322
children and mothers enrolled in the Danish National Birth Cohort
between 1996 and 2002.
More than half - 56 percent - of mothers reported using
acetaminophen during pregnancy.
Children born to these women were 37 percent more likely to be
diagnosed with hyperkinetic disorder (HKD), a severe form of ADHD.
They were 29 percent more likely to be prescribed ADHD medications,
and 13 percent more likely to exhibit ADHD-like behaviors at age 7.
The acetaminophen-ADHD link was stronger for women who used the
medication during more than one trimester of pregnancy, and
increased with the frequency of exposure.
Five to six percent of babies born today will develop ADHD symptoms
during their lifetimes, Dr. Olsen noted; based on the current
findings, that risk would increase to about 7 percent for children
exposed to acetaminophen prenatally.
"It's still a modest increase," he said. "For the women that are
taking these drugs there are no special reasons for concern....for
women who are pregnant and who have not taken these drugs, I think
that the take-home message would be a lot of the use of these
particular drugs during pregnancy is not really necessary."
[to top of second column]
An editorial accompanying the study pointed out that Olsen's team
adjusted for things that might have also influenced fetal
development, such as the mothers' inflammation or fever, while
possibly explaining why the women took acetaminophen. But the
researchers could not account for every reason the women took
acetaminophen, so more study is needed.
Pregnant women should consult their physician about whether or
not they should be taking acetaminophen during pregnancy, one of the
editorial's coauthors, Dr. Kate Langley, told Reuters Health.
Even if acetaminophen exposure does turn out to have a causal
relationship with ADHD, she added, it is only one of many
environmental and genetic risk factors involved in the disease, said
Langley, a professor of psychology at Cardiff University and the MRC
Center for Neuropsychiatric Genetics and Genomics.
"In terms of research, it's definitely something that should be
followed up, but it's the first step on a long road to try to
determine how we should interpret these findings," she said.
and http://bit.ly/MrXxLE JAMA
Pediatrics, online February 24, 2014.
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