KNOXVILLE — In a new study released Thursday, children born in August have a significantly higher diagnosis and treatment rate of Attention-Deficit/Hyperactivity Disorder compared to children born in September.

The study, published in The New England Journal of Medicine, used insurance data to track several hundred thousand children born between 2007 and 2009 and followed until 2016.

The study says:

"Younger children in a school grade cohort may be more likely to receive a diagnosis of attention deficit–hyperactivity disorder (ADHD) than their older peers because of age-based variation in behavior that may be attributed to ADHD rather than to the younger age of the children."

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The study did not look at states that did not have a Sept. 1 cut off.

Tennessee's cutoff date for entering Kindergarten, which is mandated by state law, is Aug. 15.

That means a child must be five years old on or before that date to enroll in school for the year.

The authors of the study wrote a piece on their research in the New York Times.

In the article, they say:

"We believe these findings reveal just how subjective the diagnosis of ADHD can be. In any given class, inattentive behavior among younger, August-born children may be perceived, in some instances, to reflect symptoms of ADHD, 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."

Dr. Debbie Christiansen is a developmental-behavioral pediatrician at East Tennessee Children's Hospital.

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"A lot of things in medicine are subjective," Christiansen said. "It's not just ADHD."

She says the study has good points, but should be taken with full context.

"I think it brings to light to fact that we need to be careful when we make a diagnosis," Christiansen said. "You need to look at lots of things and take lots of things into consideration and you don't need to rush to make a diagnosis."

Dr. Robert Devereaux is a psychologist at Thriveworks in Knoxville.

He says the study shows parents should consider holding their child back in school if they're born close the age cut off.

"Perhaps waiting a little more time, or being a little more considerate of that may be really helpful instead of just jumping the gun because all of their friends are starting school. They may just simply not be ready."

Dr. Christiansen says testing can be time consuming, but encouraged parents to make sure they do what they can to get the right diagnosis.