Team McCallum

R&D for Lifetime of Life

ADHD misdiagnosed.

Two completely separate studies published in the Journal of Health Economics have both concluded that many US schoolchildren are being misdiagnosed with ADHD based on their birthday and the cut-off date for school year entry.

Children born just after the cutoff, who are relatively old-for-grade, have a significantly lower incidence of ADHD diagnosis and treatment compared with similar children born just before the cutoff date, who are relatively young-for-grade.

According to Prof William N Evans “Since ADHD is an underlying neurological problem where incidence rates should not change dramatically from one birth date to the next, these results suggest that age relative to peers in class, and the resulting differences in behavior, directly affects a child’s probability of being diagnosed with and treated for ADHD.”

In the second study, Prof Todd Elder found the youngest in a year had a 60% higher rate of being diagnosed with ADHD. When that group of classmates reached the fifth and eighth grades, the youngest were more than twice as likely to be prescribed stimulants.

The effect held true across states with varied cut-off dates. No matter whether the cut-off was 1st Sep (15 states) or 1st Dec (Michigan), those just squeezing in had low rates of ADHD and those missing out by a day had high rates of ADHD.

Overall, this study found that about 20% – or 900,000 – of the 4.5 million children currently identified as having ADHD are likely to have been misdiagnosed.


August 18, 2010 - Posted by | ADHD, Child Health, Success, Todd Elder, United States, William N Evans

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