Does Younger School Entry Increase ADHD Diagnosis Rate?

Mother and daughter on first day of schoolChildren who are younger than their classmates are more likely to be diagnosed with attention-deficit hyperactivity (ADHD), according to a study in The Journal of Pediatrics.

According to the United States Centers for Disease Control and Prevention (CDC), 10.1% of all children ages 5-17 were diagnosed with ADHD during the statistical gathering period of 2011-2013. Among boys, diagnosis rates were much higher, at 14%, compared to 5.9% among girls.

Does Young Age Increase Likelihood of ADHD Diagnosis?

Led by Dr. Mu-Hong Chen, researchers examined data on 378,881 children from Taipei and Taoyuan, Taiwan. The children ranged in age from 4 to 17 between 1997 and 2011. In Taiwan, the annual school enrollment birth date cutoff is August 31, so children born after this date must register for a grade level below that of children born before August 31.

Researchers compared the youngest children (born just before the cutoff in August) to the oldest children (born just after the cutoff in September). Preschool and elementary school children were more likely to be diagnosed with ADHD or receive ADHD medication if they were among the youngest in their grade.

The correlation did not hold for adolescents, suggesting the overall likelihood of being diagnosed with ADHD decreases with age.

ADHD or Immaturity?

Though researchers only looked at Taiwanese children, previous research suggests similar outcomes may occur for other children. A 2012 study of Canadian children also pointed to the role of age in ADHD diagnosis rates. In that study, kindergarten children were 30% more likely to be diagnosed with ADHD and 41% more likely to receive ADHD medication if they were among the youngest in their class. By first grade, younger children were 70% more likely to receive an ADHD diagnosis, and 77% more likely to be prescribed ADHD medication.

Neither study directly tested a causal connection between age and diagnosis rates. The authors of both studies point to concerns about diagnosing children with ADHD when age and maturity level might contributing factors.


  1. ADHD or just immature? (2016, March 10). Elsevier Health Sciences. Retrieved from
  2. Attention Deficit Hyperactivity Disorder (ADHD). (2016, January 4). Retrieved from
  3. Neale, T. (2012, March 5). Starting school early may affect ADHD diagnosis. MedPage Today. Retrieved from
  4. Nierenberg, C. (2016, March 10). Birth date may influence child’s risk for ADHD diagnosis. Retrieved from

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  • Richard


    March 14th, 2016 at 10:34 AM

    There are simply too many people for whom the answer of being immature is for some reason insufficient to them.
    Being immature doesn’t seem like anything that is fixable, but hey, if I say that they are hyperactive then maybe there is a pill that can help with that.
    That is some flawed thinking right there.

  • christina Z

    christina Z

    March 14th, 2016 at 4:34 PM

    Why do you think that there are now all of these parents holding their kids back a year, usually in kindergarten? They don’t want them to get stymied my a misdiagnosis like can so easily happen as well as to give them an academic leg up. It seems that this is the new trend.

  • Matthis


    March 15th, 2016 at 2:37 PM

    This could have a lot to do with how certain kids are diagnosed. I would think that much of it too will come from the teachers in the classroom, the parents, and how the doctor overall usually works with these types of cases.

  • Emily T

    Emily T

    March 17th, 2016 at 11:27 AM

    This is a pretty interesting theory but I still am not too sure that it holds water overall. I do think that there are some kids who are just immature and they get this label slapped on them a little too soon without much in the way of research and testing. But I also think that there could be something environmentally going on that would cause the spike in numbers. Kids are not entering school today any younger than they always have and yet the numbers of diagnoses has gone way up. There is something going on that we just have not been able to work fully out yet.

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