Aug. 19, 2010 -- If your child is the youngest in the class and has a diagnosis of ADHD -- attention deficit hyperactivity disorder, marked by inattention and impulsiveness -- it may be a mistake, researchers say.
What is actually immaturity may be mislabeled as ADHD, according to new studies.
''It's not just how old you are when you enter kindergarten that matters," says researcher Todd Elder, PhD, a health economist at Michigan State University, East Lansing. "It's how old you are relevant to your classmates."
Likewise, if your child is the oldest in the class and doesn't have a diagnosis of ADHD, that, too could be wrong, Elder says.
Although recent headlines from his research have focused on the possibility that nearly 1 million children in the U.S. may have been misdiagnosed with ADHD, Elder tells WebMD that there may also be a substantial amount of underdiagnosis among older kids.
The research is slated to publish in the Journal of Health Economics.
Is It Really ADHD? A Closer Look
In his study, Elder looked at the differences in ADHD and medication rates between the oldest and youngest children in a grade. He used data from the Early Childhood Longitudinal Study Kindergarten Cohort, funded by the National Center for Education Statistics.
He looked at whether and how the age of a child relevant to his classmates made a difference. He also looked at which child was likely to take ADHD medications and if the patterns differed by states, which have different cutoff dates for when a child can enter kindergarten.
He found that the youngest children in kindergarten were 60% more likely to be diagnosed with ADHD than their oldest classmates, which could translate to 900,000 children potentially misdiagnosed. They were more likely to be on ADHD medications than the older kids.
What is it about the peer group that may influence a misdiagnosis of ADHD? ''I'm not entirely sure," Elder says. "Diagnoses are explicitly based on a comparison of a kid's behaviors with those of their peers."
Kids in the same grade and kids of the same age are two very different scenarios, he says.
Is It Really ADHD? Another Look
In a similar study, Melinda Morrill, PhD, a research assistant professor of economics at North Carolina State University in Raleigh, and her colleagues looked at data from two national health surveys and a national private health insurance claims database to evaluate ADHD diagnosis and treatment in children. The time period studied was from 1996 to 2006.
"The basic idea is, we compared children born just a few days apart," she tells WebMD, including older kids who made the kindergarten cutoff and younger kids who did not. "We found very different rates of diagnosis and treatment."
''Children born before the cutoff have a 25% higher rate of ADHD diagnosis than children born after the cutoff for kindergarten eligibility," she says. "That's huge."
In her national sample, she says, the average diagnosis rate of ADHD is 8%. Children born before the cutoff had a rate of 9.7%, she says, and children born after (the older kids in a class) had a rate of 7.6%.
She can't say why, as that's beyond the study's scope. "All we show is that we have this pattern," she says.
She agrees with Elder: ''Immaturity could be mistaken for ADHD."
Is It Really ADHD? Second Opinions
James Perrin, MD, a spokesman for the American Academy of Pediatrics and head of the division of general pediatrics at Massachusetts General Hospital for Children, Boston, is skeptical that a million children may be misdiagnosed.
''It's not an easy diagnosis to make," he says of ADHD. "There is subjectivity."
Parents should get two opinions, he says. "We do recommend there be an independent verification," says Perrin, who has consulted for pharmaceutical companies that make medications for ADHD.
If the diagnosis is ADHD, environmental changes as well as medication are recommended, Perrin says, not medication alone. "It may be the child is in the wrong environment."
Another expert, George Kapalka, PhD, of Monmouth University in Long Branch, N.J., who has researched ADHD, doesn't dispute there are misdiagnoses. "We should strive to diminish those," he tells WebMD.
But, he adds, criteria for diagnosing ADHD ''clearly indicate impairment must be present in at least two settings, so the diagnosis should never be made based on school problems alone."
More Tips for Parents
Consider a child's age, not grade, Elder says, when a diagnosis of ADHD is suspected. "If your child is the youngest in the classroom, and the teacher says 'ADHD,' I would try to get multiple opinions."
''Parents should know about this," Morrill says of her research findings, ''and think about whether their child is behaving normally for their age group, not just relevant to their classroom peers."