Why so many children in America have ADHD

Few things agitate Robert F. Kennedy junior, America’s new health secretary, more than the rate of attention-deficit hyperactivity disorder (ADHD) among American children. And for good reason: one in nine children aged 3-17 years has been diagnosed with ADHD, two to three times the rate in other Western countries. On February 13th, Mr Kennedy’s first day in office, President Donald Trump put him in charge of a special commission tasked with working out, in the next 100 days, why so many American children have ADHD and other chronic conditions.

There are reasons to worry that the commission will miss the mark. Its terms of reference mirror Mr Kennedy’s beliefs. He blames ADHD on the rampant use of chemicals by America’s food industry. While there is scientific evidence that artificial food colours can worsen some ADHD symptoms in children, their role is marginal. The actual reason why America is an outlier is widespread over-diagnosis.

A typical ADHD diagnosis in America is done by a paediatrician or a family doctor in an office visit as brief as 15 minutes. The norm in Europe is an hours-long assessment by a psychiatrist. The difference has to do with America’s scant health-insurance coverage for mental health care and lax rules about who can diagnose ADHD. Lots of corners are cut in those 15 minutes. A full ADHD assessment that follows psychiatric guidelines entails cognitive tests of the child, detailed interviews of parents and teachers and even observing the child in the classroom. This helps to rule out other causes for ADHD-like behaviour. Often, it is a child’s normal reaction to a chaotic home or classroom.

Fresh evidence of specious diagnoses landed in December, in a study published by the National Bureau of Economic Research. It found that ADHD diagnoses in America spike by 14% on Halloween compared to the ten weekdays before or after that. It is easy to guess why—the children were examined on the one very exciting day when you get to wear a fun costume and collect bucketloads of candy. Joel Nigg, a psychiatrist at Oregon Health and Science University, says that in his clinical practice he sees many cases that look like ADHD on the surface but, once fully evaluated, turn out to be something else (anxiety or a learning disability, for example).

Doctors are not alone in over-diagnosing ADHD. In a study in 2020, 10% of Americans rated their children high on a scale of ADHD symptoms, compared with 3-4% of Swedish and Norwegian parents. Cognitive tests showed that the American parents over-reported ADHD symptoms by a wide margin; the Swedish and Norwegian parents were generally accurate.

America’s ethos of “school achievement above all else” is part of the problem, says Stephen Hinshaw of the University of California at Berkeley. It does not help that Americans are bombarded with advertisements for ADHD drugs. Only America and New Zealand allow direct prescription-drug advertising to consumers.

All too often, however, the push for ADHD diagnoses comes from schools. Accountability rules can incentivise them to get ADHD diagnoses for poor-performing students: they can place children with ADHD into special-education classes and exclude their test results from reporting. Dr Hinshaw and others have found that ADHD rates are higher in states with more stringent accountability rules, especially for poor children. In Louisiana and Mississippi, poor states and early adopters of school accountability, one in six children has been diagnosed with ADHD.

At the same time, rich American parents and the competitive schools where they enroll their children have been tempted to exploit school accommodations for ADHD, such as extra time on exams.  This shows up in the data for the so-called “504 designation”, a disability category for students who are expected to learn as much as other students, with certain accommodations (their test scores are included in the school average). An analysis by The Economist found that 8.6% of secondary-school students in the most affluent areas have a 504 designation, compared to 1.4% of students in the poorest areas (see chart).

What would the ADHD rate in America be if children were diagnosed properly? According to a study of 12,000 American children published in 2022 by Dr Nigg and his colleagues, 9% of children would be categorised as having ADHD based solely on parents’ answers about symptoms. If both parents’ and teachers’ ratings were required, only about 5% of the children would have ADHD. When the researchers went further, taking into account standardised scales that show how far behaviour is from that typical for a child’s age, the ADHD rate dropped to 3.5%—falling in line with that in other Western countries.■

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