Children born to women who took antidepressants during pregnancy are statistically likelier to develop the mental disorder called ADHD, researchers said on Tuesday.
ADHD is a condition blamed for severe and frequent bouts of inattention, hyperactivity or impulsivity, often leading to problems in socialising and education. Children and young adolescents are most frequently diagnosed with it.
But, the researchers stressed, the risk of attention-deficit hyperactivity disorder (ADHD) is low in real terms and it may yet be explained by a statistical quirk.
Reporting in the journal Molecular Psychiatry, a team led by Roy Perlis at the Massachusetts General Hospital looked at the medical background of 1,377 children in New England who had been diagnosed with autism and 2,243 who had been diagnosed with ADHD.
These two groups were matched against three times as many healthy counterparts, who had neither of these disorders.
Taking antidepressants during pregnancy was associated with the risk of autism in the offspring, the study found, although this link faded away once a maternal history of severe depression was taken into account.
A similar association emerged between ADHD and antidepressants in pregnancy. However, the risk remained even when the severity of maternal depression was considered.
"This risk, modest in absolute terms, may still be a result of residual confounding," the investigators said, referring to a lingering possibility of statistical error.
And, they warned, any risk "must be balanced against the substantial consequences of untreated maternal depression".
Previous research has found that depression is a major danger for both mother-to-be and her baby, and the risk of a depressive relapse is multiplied fivefold if medication for it is discontinued during pregnancy.
Independent experts were cautious about the study, pointing to a long-running debate about the mix of genetic and environmental causes for ADHD.
Guy Goodwin, a professor of psychiatry at Britain's University of Oxford, said the level of exposure to antidepressant drugs in the womb among children in the study was "quite low".
This made it "possible, even likely" that ADHD in the offspring had a genetic cause and did not come from the medication, he told the Science Media Centre in London.
The fierce debate over ADHD includes opposition from some doctors who contest the very existence of the purported condition.
They fear the term "medicalises" problems that are really rooted in a child's personality or maturity, dud parenting or other social issues.
According to a 2013 report by the US Centers for Disease Control and Prevention (CDC), 6.8 percent of American children and teenagers have ADHD. Doctors often prescribe powerful psychostimulants such as Ritalin, sales of which have boomed in recent years.