Once children begin school, teachers play a key role in their development. Teachers are responsible for educating, observing, and reporting a child’s progress as they make their way through elementary school.

If a child is not meeting the expected benchmarks like other children in the class, there's a good chance the teacher has taken note and brought it to the attention of the parents.

One common disorder that is often noticed in classroom settings is attention deficit/hyperactivity disorder (ADHD), which can include symptoms such as fidgeting, excitability and difficulty focusing.

But a recent study published in the New England Journal of Medicine by investigators from Harvard University and Massachusetts General Hospital has identified a new factor that may impact which students are diagnosed with ADHD in the classroom setting.

Their study found that children with August birthdays in school systems that have a September 1st grade cutoff are up to 30% more likely to be diagnosed with ADHD.

Bias in the Classroom

According to the Centers for Disease control (CDC), the rate of ADHD diagnosis has been steadily increasing since 1997, and approximately 9.4% of children aged 2-17 were diagnosed with ADHD in 2016. Symptoms usually appear between the ages of three and six years-old, making kindergarten a prime time for diagnosis.

In some states, when a child begins kindergarten, there is a birthday cut-off date of September 1st. Those who turn five after the first of September must wait until the following year to enroll, creating a classroom of children that could be up to a full year apart in age.

While a year may not sound like a large gap, it is important to note how fast children develop from year-to-year when they are young.

"As children grow older, small differences in age equalize and dissipate over time, but behaviorally speaking, the difference between a 6-year-old and a 7-year-old could be quite pronounced. A normal behavior may appear anomalous relative to the child’s peer group."

Study Findings and Implications

The research team, led by Mass General's Anupam Jena, MD, PhD, referenced over 400,000 insurance claims of children and sorted them by date of birth. They found that children born in August were 35 percent more likely to be diagnosed with ADHD, with 0.8 percent of August-born children being diagnosed compared to 0.6 percent of older children. This difference was not seen in schools without a September first cut-off date.

While researchers recognize ADHD is a complicated diagnosis requiring a clinician’s expertise, the data suggest that diagnoses are not always just related to symptoms, but context as well.

If there are questions of a possible ADHD diagnosis, “A child’s age relative to his or her peers in the same grade should be taken into consideration and the reasons for referral carefully examined,” says Jena.

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