October 21, 2019
A recent study published in the New England Journal of Medicine found that children with August birthdays are diagnosed and treated for ADHD at a 34% higher rate than their peers born even a month later.
How can that be? The explanation is simpler than you might expect.
Many states use Sept. 1 as an arbitrary cutoff date to determine when children can enter Kindergarten. Five-year-olds born before Sept 1 are admitted, while those born after must wait another year to enroll.
You can see how this plays out: A child who turns 5 on Aug 20th will be one of the youngest in her class—maybe by as much as 11-plus months. In contrast her classmate born Sept 20th will be one of the oldest in the class. With nearly a year less development under their belts, the younger kids may be apt to be easily distracted, and behave in ways associated with ADHD—not because they have the condition, but because they are less mature than their classmates.
Because an ADHD diagnosis in young children is largely subjective, the observations of parents, teachers, and health care providers might result in interpreting age-appropriate inattentive behavior as a symptom of ADHD, if birth date is not factored into the evaluation.
Writing in The New York Times, health policy researchers Anupam B. Jena, Michael Barnett, and Timothy Layton explain the potential for inappropriate or overdiagnosis and the potential harm that may follow:
We believe these findings reveal just how subjective the diagnosis of A.D.H.D. can be. In any given class, inattentive behavior among younger, August-born children may be perceived, in some instances, to reflect symptoms of A.D.H.D., rather than the relative immaturity that is biologically determined and to be expected among children who are nearly one year younger than September-born classmates.
The stakes of additional, potentially inappropriate diagnoses are high, particularly when diagnoses are accompanied by medical treatment, which has side effects. In cases where A.D.H.D. is appropriately diagnosed, we know that behavioral and medical treatments can improve concentration and school performance and other outcomes. And in these instances, the harms of medical treatments are, on average, outweighed by the benefits. But when the disease is improperly diagnosed, the clinical harms and dollar costs of treatment may not be met with commensurate benefits.
This study is not the first to reach these conclusions, however, it is considered stronger than previous research because of the large sample size, and the careful study design.
At the very least, this is a wake-up call for parents, doctors, teachers, and evaluators that an ADHD assessment—particularly for young children—must take into consideration the child’s birth date.