New Study Finds A Correlation Between ADHD Diagnosis and School Enrollment Date

The younger children are when they enter school, the more likely they are to be diagnosed with ADHD, a new study says.

A study led by Harvard Medical School researchers and published in the New England Journal of Medicine shows a correlation between children born in August who have a school cutoff date of Sept. 1 and an ADHD diagnosis. In fact, children with August birthdays in these states are 30 percent more likely to be diagnosed with ADHD when compared with their older peers in the same grade.

ADHD diagnosis - The Everyday Mom Life

The study suggests that the diagnosis, which has risen dramatically in the past 20 years, may be a factor of earlier school enrollment and immaturity for the classroom’s youngest students.

Immaturity vs. ADHD

“Our findings suggest the possibility that large numbers of kids are being over-diagnosed and over-treated for ADHD because they happen to be relatively immature compared to their older classmates in the early years of elementary school,” said study lead author Timothy Layton, assistant professor of health care policy in the Blavatnik Institute at Harvard Medical School.

Most states have random cut off dates for children starting school. In states where the cutoff is Sept. 1, a child born on August 31 will be a full year younger than some of their peers.

The younger a child is the more trouble they may have sitting still and concentrating for long periods of time in class, Layton said. Extra fidgeting may lead to a medical referral followed by diagnosis and treatment for ADHD, he continued.

For instance, normal, energetic and noisy behavior for a 6-year-old could seem relatively abnormal when comparing him or her to a 7-year-old peer. Researchers stated that this may be particularly true for younger children because an 11 to 12-month difference in age could lead to significant behavior differences for young students.

“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,” said study senior author Anupam Jena, the Ruth L. Newhouse Associate Professor of Health Care Policy in the Blavatnik Institute at Harvard Medical School and an internal medicine physician at Massachusetts General Hospital. “A normal behavior may appear anomalous relative to the child’s peer group.”

Study Analysis

Researchers used the records of a large insurance agency database and compared the different in ADHD diagnosis by birth month. They looked at August versus September and compared more than 407,000 elementary school children born between 2007 and 2009, and who were followed through the end of 2015.

The analysis showed 85 out of 100,000 students born in August were either diagnosed with or treated for ADHD, compared with 64 students per 100,000 born in September.

Looking at ADHD treatment only, investigators also observed a significant difference in that 53 of 100,000 students born in August received ADHD medication, compared with 40 of 100,000 for those born in September.

Jena added that a 2017 working paper from the National Bureau of Economic Research suggests children born just after the cutoff date of Sept. 1 also tend to have better long-term educational performance when compared to their younger peers born just before the cut off date.

“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,” Jena said.

Complex Diagnosis

However, Jena cautions that the reasons for the rise in ADHD are complex and multifaceted and that cutoff dates are likely just one of the many reasons.

“The diagnosis of this condition is not just related to the symptoms, it’s related to the context,” he said. “The relative age of the kids in class, laws and regulations, and other circumstances all come together.”

Oddly, no differences were observed between children born in August and September in states with cutoff dates other than Sept. 1 for school enrollment.

You can find the abstract and the whole study click here

For more news and research, click here.


  1. My oldest son had a summer birthday so he had a hard time sitting still in class. The teachers tried to label him with ADHD but I instead worked with him and he did just fine in school.

  2. Hmm, that’s an interesting finding. Our school has a cutoff date different than other surrounding districts. I wonder if they have seen a higher percentage in our school.

  3. This is so interesting to know, especially since I find that kids are going to school younger and younger! Do you think there shouldn’t be strict cut off dates?

  4. This is for sure so interesting to know especially for parents of the school age kids like me. I will be more careful with my kid for sure after reading this!

  5. Oh my gosh!! I am SO glad this was done. I noticed this with my own kids – my daughter started a year earlier and had so many more issues than my sons. It seems like a good thing to start them early but it really isn’t.

  6. ADHD seems quite common to label a very active child usually younger than his/her classmates. Teachers should work on an active little child rather stressing parents for natural active little child behavior.

  7. What an interesting study. I think it does depend on the child. For instance, my sister was born in December and was ready to start kindergarten when she was 4, while my brother was a September baby and waited till the following year because he wasn’t ready maturity wise.

  8. I am not too familiar on ADHD but this may help other parents who are having children that having the same issue. Great post anyway.

  9. Wow, this study makes a lot of sense. It probably depends on the child’s immaturity too. Thank you for sharing this, I will have to keep it in mind for when I have children!

  10. I didn’t know this. I’ve been wondering about our second child. He turns school-age in November, which means he doesn’t make the cut-off date. Good to know that a year more means they’ll be able to better participate in class.

  11. Is that so? And I really wonder here in our country the Philippnes why our department of education is so obsessed about getting kids to a certain level at a certain age even when they are not ready.

  12. I think that some teachers who may be overwhelmed and probably should be in a different career entirely are far too quick to label a child as ADHD, ADD, or simply “bad” because the child is being a child and not a small adult. These findings are very interesting and bring up some very valid point about the mental maturity differences between a 6-year-old and a 7-year-old.

  13. This is so interesting! I’ve long maintained that schools often expect behaviors above the developmental level of the kids they teach. I found it interesting that my associate’s in early childhood development always covered development and readiness more extensively than a bachelor’s in elementary education.

  14. Wow, what an incredible article! It makes a lot of sense, and it’s great that researchers are finding these correlations in order to better understand diagnoses such as ADHD.

  15. Oh wow. This is quite interesting study that Harvard did. It’s weird that ever since ADHD was discovered, all energetic kids have been diagnosed with ADHD. Odd as it seems.


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