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Kids who start kindergarten young are more likely to be diagnosed with ADHD

There’s a growing concern about overdiagnosis of ADHD, since the treatment can come with adverse effects.

More than 5 percent of US children are on an ADHD drug.
Getty Images/Blend Images

Timothy Layton, an assistant professor of health care policy at Harvard University, has a son who was born in August. Just before he was supposed to start kindergarten in 2017, Layton read a research paper showing that kids born in August scored worse at school on a range of academic and behavioral measures compared to older kids in their class.

“The research suggested the youngest kids in the class have an uphill battle throughout their time in school because they are younger,” said Layton. And it made such an impression, he and his wife decided to hold their son back a year. “We thought we’d do the opposite — and give him an advantage.”

Layton then went on to explore a related phenomenon in his research: How do kids born in August, like his son, compare to September babies when it comes to rates of attention deficit hyperactivity disorder diagnosis? He and several colleagues already knew that ADHD rates were surging, and that there was a great deal of variation in diagnosis rates among states. Three times as many kids are diagnosed with ADHD in Arkansas compared to Nevada, for example. So they wondered if birthdays were driving the trend: Were the younger children in a kindergarten class more likely to be diagnosed?

In a paper recently published in the New England Journal of Medicine, Layton and his co-authors found that, yes, birthdays matter hugely when it comes to ADHD diagnosis. What more, younger children who are just immature are being diagnosed for reasons that have nothing to do with their actual medical need.

For context, many states impose age cutoffs for entry to kindergarten. In 18 states, children whose fifth birthdays happen by September 1 can start kindergarten the year they turn 5, while kids who reach 5 after that date need to wait a year.

The researchers looked at the insurance claims for more than 400,000 children across the US who were born between 2007 and 2009 and followed until 2015. And they found that in states where kids must be 5 years old by September 1, August-born children had an ADHD diagnosis rate of 85 per 10,000 children. Kids born in September, meanwhile, had a much lower rate of diagnosis, at 64 per 10,000 kids. That’s an absolute difference of 21 diagnoses per 10,000 children, and this trend didn’t emerge in states with different age cutoffs.

What the study shows, says Layton, is that “diagnosis and treatment of ADHD is still very subjective.” And it may be one piece of the puzzle in explaining why the prevalence rate in kids has grown from 3 and 7 percent historically to 11 percent today — a level many researchers say is too high.

Considering that more than 5 percent of US children are now on an ADHD drug, and that the drugs can come with heavy side effects, the research also suggests some children taking ADHD medications could be exposed to risks for no reason at all.

What is ADHD?

ADHD as a medical diagnosis has been around for a long time, though under different names. In the first quarter of the century, it was called hyperkinesis. Then along came hyperkinetic disease. Now, it’s attention deficit hyperactivity disorder.

There’s still a lot that researchers don’t understand about what causes ADHD, but it’s become clearer that genes play a role. And over the years, there’s been a growing awareness that there is a neurological basis for the attention issues and hyperactive, impulsive behaviors associated with the disorder.

Today, ADHD is one of the most common neurodevelopmental problems in childhood, and it’s diagnosed when normal characteristics of being a kid — being inattentive, fidgeting a lot — become disruptive. There’s no biological marker, like a blood test, that can identify ADHD, so doctors have to look out for symptoms and try to understand whether those symptoms impede with a child’s academic performance or social interactions before making the diagnosis.

“Just having those behaviors doesn’t mean you have ADHD,” said Martin Stein, a professor of pediatrics at the UC San Diego School of Medicine. “The behaviors have to be associated with impairment.”

But making a diagnosis can be difficult and take months. Clinicians need to get to know the child and go through several steps to assess him or her — and they don’t always have that time, explained Michael Manos, the clinical director of the Cleveland Clinic’s ADHD Center for Evaluation and Treatment.

A proper assessment involves determining what ADHD symptoms a kid has and how those symptoms disrupt their lives, and then ruling out other potential causes of symptoms, such as depression or anxiety. “The diagnosis is no just looking at a rating scale and listening to a parent’s brief description of behavior,” Manos added. “You have to be careful to go through the other steps.”

The rate of ADHD diagnosis has surged, due in part to pharmaceutical marketing

This difficulty diagnosing the disorder, more awareness about it, and a years-long campaign by pharmaceutical companies to increase the number of people on their medications means more children are now being diagnosed with the condition.

Over the past two decades, the makers of ADHD drugs have heavily marketed the disorder and promoted their pills to doctors, educators, parents, and even kids — through medical education, magazine and TV ads, and comic books.

According to an exposé in the New York Times, this campaign:

stretched the image of classic ADHD to include relatively normal behavior like carelessness and impatience, and has often overstated the pills’ benefits. The Food and Drug Administration has cited every major ADHD drug — stimulants like Adderall, Concerta, Focalin and Vyvanse, and nonstimulants like Intuniv and Strattera — for false and misleading advertising since 2000, some multiple times.

The results of this pharma campaign have been remarkable: Over the past 20 years, by just about every measure, the rates of diagnosis and treatment have surged in the US. According to the National Institutes of Health, the prevalence of children ever diagnosed with ADHD increased by 42 percent between 2003 (when it was 8 percent) and 2011 (when it was 11 percent). Some of the latest data, from 2015-’16, shows 10 percent of children and adolescents ages 4 to 17 were diagnosed with ADHD in the US.

And Layton’s study isn’t the first to find evidence that ADHD diagnoses may be missing the mark. In a 2018 review of 19 studies from 13 countries involving more than 15 million children, researchers found the same link — younger kids were more likely to be diagnosed in 17 of the 19 studies. “It is the norm internationally for the youngest children in a classroom to be at increased risk of being medicated for ADHD, even in jurisdictions with relatively low prescribing rates,” the authors concluded. Again, that means factors other than medical need are driving ADHD diagnoses and potentially leading to overtreatment of kids who are neurologically healthy.

There’s a growing concern about the harms of treatment

There are just two evidence-based treatments for ADHD, according to the American Academy of Pediatrics’ ADHD guidelines: behavioral therapy and pharmaceutical drugs. Depending on the age of the child, these two approaches can be tried either alone or in combination. But there’s also worrying evidence about the side effects of some of the most popular ADHD drugs.

For example, the AAP suggests doctors prescribe methylphenidate (sold under brand names including Ritalin) to preschool-age children when behavioral therapy fails or isn’t available. A 2018 Cochrane Review of randomized controlled trials on methylphenidate in children and adolescents found about one in 100 patients treated with the drug suffered a serious adverse event, including death, cardiac problems, and psychotic disorders. While the quality of the evidence was low, the authors said these harms were serious enough to suggest “clinicians and parents are alert to the importance of monitoring adverse events in a systematic, meticulous manner.”

The Cochrane Review on the use of amphetamines (sold under brand names including Adderall) for ADHD in children was no more reassuring. While the drugs seemed to improve the core symptoms of ADHD over the short term, “they were also linked to a higher risk of experiencing adverse events such as sleep problems, decreased appetite, and stomach pain.”

This doesn’t mean no one should take these drugs, Stein said. When a child is properly diagnosed, treated, and followed up with, most respond to first-line medications and benefit from them, seeing improved school performance and concentration. But the question is: Was the child accurately diagnosed? And evidence from the birthday studies suggests that many are not, and are being exposed to serious risks for no reason.

For now, Layton said doctors need to think twice before labeling a child with ADHD. “If the child has a birthday close to the cutoff for their school year, we need to pause.”

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