Kids who are the youngest in their grade may be overmedicated for attention deficit hyperactivity disorder (ADHD), according to a Norwegian researcher who studied prescribing data.

Those who were also born preterm were at particular risk of being overmedicated, said Dr. Christine Strand Bachmann, a pediatrician at St. Olav’s University Hospital in Trondheim and PhD candidate at the Norwegian University of Science and Technology (NTNU) in Torgarden.

The study included Norwegian children born between 1989 and 1998, about 488,000 in all.

“We found major differences in the prescription of ADHD medication,” Bachmann said in an NTNU news release. “Children born in November-December had an 80% higher risk of being prescribed ADHD medication, compared to those born in January-February. This finding applies to children who were born at term.”

She and her colleagues reviewed all prescriptions kids received from age 10 to 23, comparing those born in January or February with those born in November or December.

Bachmann said the increased ADHD medication for the youngest kids owes to the way school systems are organized.

“Put simply, it looks like we’re medicating the most immature children because we’re comparing them to their oldest classmates, who are a whole year older,” she said.

“This shouldn’t be the basis for receiving an ADHD diagnosis,” Bachmann added.

Adults have to expect that a child born in November is going to be less mature than a child born in February of the same year, she said.

“Of course, we can’t stop diagnosing ADHD and giving medicine to those who need it,” Bachmann said. “But what we see here is something else.”

Children who were born before the 37th week of pregnancy had higher use of ADHD medication than their full-term classmates, the study also found.

“In that sense, the youngest premature children carry a double burden,” Bachmann said. “The disadvantage of being born late in the year comes on top of the disadvantages of being a preemie.”

While use of ADHD medications decreased with age for the young, full-term children, that didn’t happen with those born prematurely, the study found.

Bachmann said it appears that preemies are extra susceptible to the negative effect of being the youngest in school.

“Perhaps they experience falling short in the classroom, in gym and in social contexts, compared to their peers,” she said. “And perhaps the negative experiences settle in the body in a different way and to a greater extent in those born prematurely.”

Kids with ADHD often have difficulties with concentration, hyperactivity and impulsivity.

Bachmann suggested that younger students be assessed individually to determine whether they should wait a year to start school.

In Denmark, which has a flexible approach to starting school, studies do not show an increased use of ADHD meds among the youngest kids in class, Bachmann pointed out. About 40% of Danish kids born in October, November or December postpone their school start for a year.

“Premature babies born late in the year could especially benefit from this approach,” Bachmann said, emphasizing that she is not advocating that all children born in the fall should start school later.

“We think this could be relevant for the most vulnerable children,” she said, adding that kids should be individually assessed.

The study found similar age effects for other medications while assessing drugs for depression, anxiety, psychoses and sleep, but those gaps disappeared through the teen and early adult years.

The findings were recently published in the journal Pediatrics.

More information

The U.S. Centers for Disease Control and Prevention has more on ADHD.

SOURCE: Norwegian University of Science and Technology, news release, Dec. 12, 2022