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Could being born in August make an ADHD diagnosis more likely?

Kindergartners who start school earlier may have a greater risk of being diagnosed and treated for attention deficit and hyperactivity disorder simply because of the timing of their birthdays, a new study published in the New England Journal of Medicine suggests.

The study explored insurance claims data to compare the rate of ADHD diagnoses among thousands of children with August and September birthdays. They found that children with August birthdays were more likely to be diagnosed with the disorder, in part, researchers suspect, because their relative maturity may make them more challenging to teach.

More than 6 million U.S. children have been diagnosed with ADHD, the most common neurobehavioral disorder during childhood. That number that has doubled in less than two decades. According to the Centers for Disease Control and Prevention, children with ADHD easily lose focus or misbehave, and these behaviors do not improve over time. The study is among a growing body of research about the diagnosis and treatment of the disorder — including when and whether kids are being labeled for exhibiting behavior appropriate for their ages.

Here’s a look at the study’s findings and why they matter.

What the study found

In the study, funded by the National Institutes of Health, anonymous insurance claims were analyzed from Truven Health Marketscan Research Database, which has more than 80 million enrollees across the country. Researchers focused on claims from more than 407,000 U.S. children born between 2007 and 2009, and followed those cases until 2015. They looked only at cases covered by private insurance, since the database does not include people whose health care is covered by Medicaid or who are uninsured.

In the 18 states with a Sept. 1 cutoff for kindergarten enrollment, researchers found the rate of ADHD diagnosis among children with August birthdays was 34 percent higher than among children with September birthdays (the oldest in their classrooms). Out of 10,000 August-born kids, 85.1 were diagnosed with the disorder, in contrast to 63.6 out of 10,000 September-born kids.

Children born in August received treatment for ADHD at a rate of 52.9 per 10,000 children, compared to 40.4 per 10,000 children born in September who were treated for ADHD. That means children born in August in these states faced a 32-percent higher rate of ADHD treatment than their September-born peers, according to the study. In treating ADHD, physicians are encouraged to recommend behavioral therapy, such as parent training, for children ages 4 to 5 as a first course of action, according to the CDC. If medication is required, the Food and Drug Administration has approved use of stimulants, which often contain methylphenidate and amphetamine, and non-stimulants, such as atomoxetine, guanfacine and clonidine, to treat and manage a child’s symptoms.

These significant differences didn’t emerge in comparisons between children born in other pairs of months, nor did they show up in states that do not cut off kindergarten enrollment in September, researchers noted.

Beyond excluded data, the study was limited because researchers couldn’t determine if ADHD diagnoses were appropriate or if treatment produced positive outcomes for a child’s behavior. They also had no way of connecting a child’s insurance claim to their school enrollment status or when they entered school.

How common is ADHD among young children?

In 1995, 1.5 million children were receiving medication for attention deficit and hyperactivity disorder, or ADHD. By 2011, that figure more than doubled to 3.5 million children getting treatment, and 6.4 million children diagnosed with ADHD.

Pediatrician Joseph Hagan, who has practiced for nearly 40 years, said physician awareness of ADHD is far more sophisticated than it was two decades ago. Part of that has meant more children are diagnosed.

Hagan said he has diagnosed 5-year-olds — i.e. kindergarten-age kids — with the disorder and prescribed them medication, but always with an abundance of caution. Why? Current guidelines were designed to apply to children age 6 or older, said Hagan, who helped write the American Academy of Pediatrics’ recommendations for how the clinical community should approach ADHD in children. Diagnosing this disorder in younger children is “trickier,” he said, and requires a higher level of care.

It can be hard at that age to distinguish between true symptoms of ADHD, and growing pains that come along with learning how to behave in school.

Hagan said that if a doctor is going to “overdiagnose,” it is most likely going to happen within this age group, adding, “You don’t want to overdiagnose.”

Beyond observing inattentiveness, impulsivity or a combination of the two, Hagan said that to diagnose ADHD, a physician must first evaluate that:

  • A child must present at least six of nine criteria that negatively influence their daily life, such as troublesome impulsive acts and speaking without thinking.
  • Associated behaviors must appear in more than one environment, not only at home or only in the classroom (because “it’s the way your brain works”).
  • Those behaviors shouldn’t be explained by psychological conditions that mimic ADHD, such as stress, anxiety or trauma.

For children ages 4 to 5, the guidelines suggest behavioral therapies should be the first line of defense for parents and teachers.

Children and adults remain far more likely to be diagnosed with ADHD in the United States than those in the United Kingdom, according to a study published in September in the journal Lancet. Worldwide. This neurobehavioral disorder, typically diagnosed during childhood, is found in as many as 7 percent of children. The diagnosis often lasts until adulthood.

Access to and use of medication to treat diagnosed cases of the disorder are on the rise, both in the U.S. and around the globe, the study said.

But in the United States, there has been significant pushback in recent years about the unintended consequences of misdiagnosing children with ADHD and then unnecessarily medicating them.

In 2018, more than two dozen states cut off kindergarten enrollment during the month of September, according to data from the National Center for Education Statistics. This wasn’t always the case. In 1975, only nine states enrolled incoming kindergarteners if their birthday came by September, a 2012 report from the Education Commission of the States found.

Why it matters

In 2017, health economist Tim Layton had just enrolled his son in kindergarten until the Harvard University assistant professor saw a study that stopped him in his tracks. Its findings suggested people born in August were predisposed to all kinds of bad things in life — everything from dropping out of school to ending up in jail. While, of course, ADHD can be managed and treated, his son’s birthday was in late August, and Layton “decided to hold him back largely because of the findings of that paper.”

That paper also inspired Layton to wonder how a young child’s birth date could set them up for negative comparisons with their peers simply because they were at a disadvantage in their relative maturity. Were these kids more likely to be diagnosed with and treated for ADHD than their older classmates? His questions led him and Harvard Medical School physician Anupam Jena to author this paper.

Sometimes, Layton said, “normal behavior is getting diagnosed and treated as ADHD just purely because a child is being compared to a heterogeneous group of children, and they appear different. That leads to diagnosis and treatment of this condition.”

What now? The clinical community needs to do a better job of diagnosing along explicit conditions, Layton said “so we don’t go down this road of massive diagnosis of this condition.”

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