Brother compatible design
The researchers then compared the incidence of autism and ADHD among siblings, some who were exposed to acetaminophen in childhood and some who were not. This study design helps account for unmeasured familial factors that influence the likelihood of conditions, particularly genetics and shared environmental conditions. More than 124,000 sibling-matched children were included in the autism analysis, and more than 97,000 sibling-matched children were included in the attention-deficit/hyperactivity disorder (ADHD) analysis.
The researchers found no association between prenatal acetaminophen use and either condition. It did not matter what dose of acetaminophen was taken, during pregnancy (which trimester), how often it was taken, or how old the mother was at the time. There was simply no association between acetaminophen and autism or ADHD.
Interestingly, there was an association when the researchers dropped the sibling-matched design and instead compared children exposed to acetaminophen with those not, a finding that has emerged in other studies. But when the researchers did a “negative control” analysis and compared children whose mothers took acetaminophen before pregnancy or after birth with mothers who didn’t use the painkiller, they also saw a “biologically implausible” link.
“Collectively, these findings suggest that the positive signal observed in both conventional and negative control analyzes reflects residual familial confounding rather than a true pharmacological effect of prenatal paracetamol exposure,” the researchers said.
No association was found between acetaminophen use in pregnancy and neurodevelopmental status in children. Sweden In 2024 and Japan In 2025.
