Paracetamol Linked to Higher Autism Risk

October 31, 2019

Its use by pregnant women could affect their children, study finds.

In one of the more rigorous studies of its kind, researchers have found paracetamol use by pregnant women is linked to a higher risk of autism in their kids.

The finding, published in the journal JAMA Psychiatry, builds on recent studies in Spain and Denmark that also linked autism with maternal paracetamol use.

Those studies, however, shared a common weakness – they relied on the mothers’ self-reports to calculate total paracetamol use, a technique prone to error.

To sidestep any questions around fallible reporting, the current team, led by paediatrician Xiaobin Wang at the Johns Hopkins University Bloomberg School of Public Health in Baltimore, US, measured paracetamol levels in blood taken from the umbilical cord at birth.

Wang’s group analysed 996 children born to mothers enrolled in the Boston Birth Cohort, a study of single, non-IVF births starting in 1998 and finishing up in 2018.

The original study included more than 3000 mums and babes. Wang’s subset was chosen because there was enough cord blood remaining to do the necessary tests.

In the Boston study children were tracked for up to two decades with tests that, in some cases, included screens for autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD).

Wang’s team gathered up those data and got down to work.

They started by testing the cord blood samples for paracetamol and two of its breakdown products. Results in hand, they calculated how much drug the foetus had been exposed to in the period around birth, dividing those levels into low, medium and high.

As a double check, they zeroed in on other things that raise autism risk and might confuse the picture, including greater maternal age and weight, fever during pregnancy, extreme prematurity and very low birth weight.

Adjusting for those potential confounds, they crunched the numbers on any connection between paracetamol levels in cord blood and later diagnoses of ASD and ADHD.

The results raise the temperature on an already uncomfortably warm debate.

Babies in the high paracetamol group had a nearly fourfold increase in the odds of having ASD compared to those in the low paracetamol group. Being in the high paracetamol group also raised the odds, by nearly threefold, of a later diagnosis of ADHD.

“[C]ord biomarkers of fetal exposure to acetaminophen were associated with significantly increased risk of childhood ADHD and ASD in a dose-response fashion,” the authors write.

Notwithstanding the usual caveat that correlation does not equal causation, what might be creating this effect?

How paracetamol works is surprisingly complex, given its wide use, but it is known to inhibit an enzyme called cyclooxygenase, or COX, as part of its anti-inflammatory and painkilling effect.

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