ADHD Diagnoses Continue to Climb

A large study in California shows that more kids than ever get diagnosed with attention deficit hyperactivity disorder. Is the condition really spreading, or are we just better at detecting it?

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As more children are diagnosed with attention deficit/hyperactivity disorder (ADHD), researchers continue to struggle with understanding whether the rise is real, or primarily driven by greater awareness of the condition.

In the latest analysis, the rate of new cases of ADHD in California between 2001 and 2010 climbed for both sexes and for most ethnic and racial groups for children between the ages of 5 to 11.

But that rise doesn’t address what’s behind the growing number of cases. Are more kids truly suffering from hyperactivity and attention deficits, or are we simply better at catching children who show any symptoms?

The new research, published in JAMA Pediatrics, is among the first to offer hints at an answer. The study is not the first to suggest that ADHD diagnosis may be increasingly common, but it has important advantages over previous work, says the study’s lead author, Dr. Darios Getahun of Kaiser Permanente Southern California. For example, instead of counting all cases reported by parents and teachers (who may make mistakes and either under- or over-report cases), the new study counts only confirmed medical diagnoses by doctors. The new study also includes more children than earlier ones, by pooling health-record data from more than 840,000 kids enrolled in a health plan with the non-profit Kaiser Permanente Southern California. Those children resemble the general population of youngsters in California, Getahun says, and the study group is large enough that researchers could look not just at trends overall, but also at trends broken down by race, age group, sex, and more. And that provides some insights into whether susceptibility to ADHD itself is all that’s changing, or whether our diagnostic criteria are changing too.

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Overall, the study found that 2.5% of kids aged 5 to 11 received a new ADHD diagnosis in the year 2001. Ten years later, in 2010, that number had risen to 3.1%, a relative increase of 24% even after the scientists adjusted for factors such as age, sex, race/ethnicity, and neighborhood average income, which can each influence ADHD risk. But not every group in the study appeared to be affected equally. In fact, the sub-populations with the highest ADHD incidence also tended to be the populations that do best on other measures of health and achievement: that is, kids who are white and living in wealthier neighborhoods and households with a median household income over $70,000 per year.

Meanwhile, the results showed that Hispanic kids are usually older than average when they’re diagnosed, if they are diagnosed at all. Asians and Pacific Islanders have the lowest ADHD incidence. Altogether, the findings suggest that, even though all the kids in the study had access to health care, some may still get be getting different treatment because they face different expectations at home and in the classroom, or because their parents have different attitudes toward mental health service provision. “That variation is very important,” says Getahun.

Families of the Asian children in the study, for example, were less likely to use mental health services to diagnose or treat ADHD, while the more well-off families and well-educated white parents were more likely to access these services, perhaps to excess, as they tended to expect more for their children academically.

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But the issue of diagnosis remains controversial. On the one hand, says Getahun, “If you diagnose [ADHD] early and you initiate treatment early, the children will do better.” On the other, over-diagnosis may lead some healthy kids to take drugs they don’t need.

Just a generation ago, ADHD was considered rare. Today it’s one of the most common behavioral disorders of childhood, characterized by poor focus, lack of attention, impulsivity, and constant movement, including fidgeting and squirming. Kids with ADHD are more likely to struggle in school, to miss classes, to get injuries, and to have “troublesome relationships” with family members and classmates. Some preliminary studies have even linked ADHD in childhood to adult outcomes such as smoking and career and relationship difficulties.

The size of the study, and the variation in ADHD diagnosis rates among different populations, supports the idea that not all of the rise can be attributed to increased awareness among doctors, teachers and parents of the disorder. While risk factors for ADHD, including brain injury, preterm birth (being born more than three weeks early), exposure to alcohol and tobacco in the womb, and some environmental toxins, such as lead and possibly mercury, may be playing a role in driving the rates higher, researchers still can’t completely explain why more and more children have been diagnosed with ADHD in recent years. But parsing apart some of the cultural and economic factors that may be responsible could help them get closer to an answer.