Youngest kids in class more likely to get ADHD drugs, study finds

By Deborah Kotz, Globe Staff

Much attention has been paid to the overdiagnosis of attention deficit hyperactivity disorder in children and the over-prescription of drugs such as ritalin, but a study published this week in the journal Pediatrics indicates that certain kids -- those in the youngest third of their class -- are 50 percent more likely than their older peers to be prescribed ADHD drugs.

They’re also more likely to under-perform on math and English standardized tests administered in fourth grade, one of the factors teachers and pediatricians use to help make a diagnosis of ADHD.

“Age should be considered when evaluating children for an ADHD diagnosis and a prescription of a stimulant such as ritalin,” said study co-author Sonia Hernández-Diaz, an associate professor of epidemiology at the Harvard School of Public Health.

Previous research has found the same correlation between age and ADHD diagnoses: A March study published in the Canadian Medical Association Journal examined medical records from nearly one million 6- to 12-year-olds in British Columbia, where incoming kindergarten students need to turn five by Dec. 31. They study found that boys born in December were 30 percent more likely to receive an ADHD diagnosis than boys born in January, and that December-born girls were 70 percent more likely to get the diagnosis than those born 11 months earlier.

In the new Pediatrics study, Hernández-Diaz and her Icelandic colleagues examined standardized test scores and medical records for nearly 12,000 students aged 9 to 12 from Iceland. They found a striking drop-off in academic performance among students who were born in the last three months closest to the birthday cutoff date for entrance into the grade compared to those who were older.

Slightly more than 6 percent of children were prescribed ADHD drugs in the study; 8 percent of those in the youngest third of their class were prescribed the drugs, while 5 to 6 percent of those in the middle or oldest third took the medications. The differences were greatest for the fourth graders but persisted through seventh grade, which Hernández-Diaz said was unexpected and surprising.

Whether age factors into a child’s SAT scores or college prospects remains an unanswered question. “Researchers always assumed that academic differences due to age would completely disappear once children reached high school, but we don’t really know,” she added.

The increased likelihood of ADHD diagnoses based on a child’s age may be even more troubling given that kids prescribed Ritalin and Adderall in elementary school often remain on the drugs permanently.

Psychiatrists have argued that ADHD is a permanent condition for some that needs to be treated well into adulthood, and that’s likely the case. Other research published this week found that adults with the condition were less likely to commit crimes when they remained on their medications than when they stopped taking the drugs.

But what about children with borderline symptoms exacerbated by their young age? Should they remain on medications through their teens and into adulthood?

There’s clearly no easy answer for this issue. Some parents choose to have their children start kindergarten a year later if their birthday falls too close to the cutoff point to give them an academic and social advantage, but that doesn’t solve the problem for kids who remain the youngest in their class.

Hernández-Diaz said raising awareness that some kids may “just need more time to mature and improve in their academic performance” might help reduce ADHD overdiagnoses. “Parents and teachers need to be aware that kids may just be acting their age if they’re nearly a year younger than some of their peers and are struggling a bit emotionally and academically.”