Youngest kids in class are more likely to be diagnosed with ADHD

The difference a year makes.


The rate of ADHD diagnoses among children has risen dramatically over the past 20 years. In 2016 alone, more than 5 percent of U.S. children were being actively treated with medication for ADHD. According to experts, the rise is fueled by a combination of factors, including a greater recognition of the disorder, a true rise in the incidence of the condition and, in some cases, improper diagnosis.

In a new study by Harvard Gazette, scientists associated a positive relationship between school starting age and children’s cognitive development. The study suggests that children’s birthday put him or her at risk for an ADHD misdiagnosis, at least among children born in August who start school in states where enrollment is cut off at a Sept. 1 birth date.

The results of the new study underscore the notion that, at least in a subset of elementary school students, the diagnosis may be a factor of earlier school enrollment. Meanwhile, there is a possibility that large numbers of kids are being overdiagnosed and overtreated for ADHD. They happen to be relatively immature compared to their older classmates in the early years of elementary school.

Study lead author Timothy Layton said, “Most states have arbitrary birthdate cutoffs that determine which grade a child will be placed in and when they can start school. In states with a Sept. 1 cutoff, a child born on Aug. 31 will be nearly a full year younger on the first day of school than a classmate born on Sept. 1.”

“At this age, the younger child might have a harder time sitting still and concentrating for long periods of time in class. That extra fidgeting may lead to a medical referral followed by diagnosis and treatment for ADHD.”

Study senior author Anupam Jena said, “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.”

Scientists gathered data from a large insurance database and compared the difference in ADHD diagnosis by birth month — August versus September. They followed almost 407,000 elementary school children born between 2007 and 2009 until the end of 2015.

In states that use Sept. 1 as a cutoff date for school enrollment, children born in August had a 30 percent greater chance of an ADHD diagnosis than children born in September, the analysis showed. No such differences were observed between children born in August and September in states with cutoff dates other than Sept. 1.

When investigators looked at ADHD treatment only, the difference was also large — 53 of 10,000 students born in August received ADHD medication, compared with 40 of 10,000 for those born in September.

Research has shown wide variations in ADHD diagnosis and treatment across different regions in the U.S. ADHD diagnosis and treatment rates have also climbed dramatically over the last 20 years. In 2016 alone, more than 5 percent of all children in the U.S. were taking medication for ADHD, the authors noted. All of these factors have fueled concerns about ADHD overdiagnosis and overtreatment.

Jena said, “The reasons for the rise in ADHD incidence are complex and multifactorial. Arbitrary cutoff dates are likely just one of many variables driving this phenomenon, he added. In recent years, many states have adopted measures that hold schools accountable for identifying ADHD and give educators incentives to refer any child with symptoms suggesting ADHD for medical evaluation.”

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

“It is important to look at all of these factors before making a diagnosis and prescribing treatment. 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.”

The findings are published Nov. 28 in The New England Journal of Medicine.