The study, done by the UCLA Fielding School of Public Health in collaboration with the University of Aarhus in Denmark and published in the current online edition of JAMA Pediatrics, used the Danish National Birth Cohort, a nationwide study of pregnancies and children, to examine pregnancy complications and diseases in offspring as a function of factors operating in early life.
The researchers studied 64,322 children and mothers who were enrolled in the Danish cohort from 1996 to 2002 and obtained diagnoses of hyperkinetic disorder among the cohort’s children (at an average age of 11) from the Danish National Hospital Registry or the Danish Psychiatric Central Registry.
The researchers found that children whose mothers used acetaminophen during pregnancy were at a 13% to 37% higher risk of later receiving a hospital diagnosis of hyperkinetic disorder, being treated with ADHD medications or having ADHD-like behaviors at age 7. The longer acetaminophen was taken the stronger the associations. The risks for hyperkinetic disorder/ADHD in children were elevated 50% or more when the mothers had used the common painkiller for more than 20 weeks in pregnancy.
“The causes of ADHD and hyperkinetic disorder are not well understood, but both environmental and genetic factors clearly contribute,” said Dr. Beate Ritz, professor and chair of the department of epidemiology at the Fielding School and one of the senior authors of the paper. “We know there has been a rapid increase in childhood neurodevelopmental disorders, including ADHD, over the past decades, and it’s likely that the rise is not solely attributable to better diagnoses or parental awareness. It’s likely there are environmental components as well.”
ADHD, one of the most common neurobehavioral disorders worldwide, is characterized by inattention, hyperactivity, increased impulsivity, and motivational and emotional dysregulation. Hyperkinetic disorder is a particularly severe form of ADHD.