Youngest Kids in Grade More Likely Than Older Peers to Be Diagnosed With ADHD

March 5, 2012— -- Children who are the youngest in their grades are more likely to be diagnosed with attention deficit hyperactivity disorder (ADHD) and be prescribed medication for the condition than their peers born earlier in the same year, according to a new Canadian study.

Researchers from the University of British Columbia compared a group of more than 937,000 children between the ages of 6 and 12 and analyzed their risk of being diagnosed with ADHD and of being prescribed a medication for it.

They found that boys born in December were 30 percent more likely to be diagnosed with ADHD and 41 percent more likely to have a medication prescribed than boys born in January. The risk was even higher for girls born at the end of the year -- they were 70 percent more likely to receive a diagnosis and 77 percent more likely to get prescribed an ADHD drug. This pattern is known as the relative age effect.

Children in Canada must be born by Dec. 31 to enter kindergarten, the authors said, which means some kids in the same grade may be almost a year apart. As a result, they may be less mature than their older peers.

"It appears that a lack of maturity among the younger children in a grade is sometimes misinterpreted as representing the symptoms of the neurobehavioral disorder of ADHD," said Richard Morrow, the study's lead author. "While many children may be appropriately diagnosed and treated, a key message from our findings is that some children who appear to meet the criteria for the diagnosis may in fact be inappropriately diagnosed."

"These findings raise concerns about the potential harms of overdiagnosis and overprescribing," he added. "These include potential adverse effects on sleep, appetite and growth, and potential increased risk of cardiovascular events."

But Dr. Jim McGough, professor of clinical psychiatry at UCLA's David Geffen School of Medicine, argued that the diagnoses considered by the authors to be inappropriate may not be. ADHD is characterized by a developmentally inappropriate level of hyperactivity, impulsivity and inattention, and there are many immature children who have these issues, so ADHD may be an accurate diagnosis.

"If they meet the criteria, then they have ADHD," McGough said. "But about half the kids who are diagnosed in the first grade won't meet the criteria later on."

"We don't exactly know why they no longer meet the criteria later," said Lori Evans, clinical assistant professor of child and adolescent psychiatry at the NYU Child Study Center.

After children get diagnosed, they should be monitored carefully. Although McGough and Evans said the medications used to treat ADHD are safe, kids who don't need them shouldn't take them.

"Proper management of ADHD involves these kids getting assessed at regular intervals to determine whether to continue treatment," McGough said.

Morrow hopes the study will eventually lead clinicians and educators to consider the possible influence of relative age when it comes to assessing children for ADHD and trying to meet their developmental needs in school.

Evans added that the study highlights the importance of diagnosing children properly.

"For ADHD, we need a diagnosis in two settings. It can't just be based on behavior at school. We need to also observe their behavior at home or some other place."

She added, "The diagnosis should be made with extreme care. There are many kids out there who have ADHD and aren't receiving appropriate treatment, but we also need to make sure that kids who don't need treatment don't get it. They may just need to grow up."

Morrow said he hopes the study will eventually lead clinicians and educators to consider the possible influence of relative age when it comes to assessing children for ADHD and trying to meet their developmental needs in school.