The increase was most pronounced in minority groups, suggesting that better access to health insurance and mental health services through the Affordable Care Act may have played a role in the increase. The rate of diagnosis during this period doubled in girls, although it was still much lower than in boys.
But the researchers say they found no evidence that confirms frequent complaints that the condition is overdiagnosed or misdiagnosed.
There are significantly more cases of ADHD in the US than in other developed countries, which has led researchers to believe that Americans are overdiagnosing children. Dr. Wei Bao, lead author of the study, said in an interview that a review of studies around the world does not support this.
"I do not think overdiagnosis is the main problem," he said.
Nevertheless, these doubts persist. Dr. Stephen Hinshaw, who wrote a book in 201
"It's probably not a true epidemic of ADHD," said Hinshaw, professor of psychology at Berkeley University and professor of psychiatry at UC San Francisco. "It could be an epidemic of diagnosis."
In interpreting their findings, however, the authors of the study tied the higher numbers to a better understanding of the state of physicians and the public, new standards for diagnosis, and improved access to health insurance through the Affordable Care Act.
Because of the ACA, "some low-income families have better access to services and recommendations," said Bao, assistant professor of epidemiology at the University of Iowa College of Public Health.
The study, published in JAMA Pediatrics, used data from the National Health Interview Survey, an annual federal survey of women about 35,000 households. Between 1997 and 1998, the number of diagnoses among children increased from about 6 percent to children between 2015 and 2016 to more than 10 percent.
Advances in medical technology could also have contributed to this increase. Twenty years ago premature babies or toddlers had a heavier survival. These factors increase the risk of being diagnosed with ADHD.
The study also suggests that fewer stigmata regarding mental health care in minority communities could also lead to more people receiving ADHD diagnosis.
In the late 1990s, 7.2 percent of non-Hispanic white children, 4.7 percent of non-Hispanic black children, and 3.6 of Hispanic children were diagnosed with ADHD, according to the study.
By 2016, there were 12 percent of white children, 12.8 percent of blacks and 6.1 percent Hispanics
Over the last few decades, Hinshaw said, there has been an expanded view of who can develop ADHD. It is no longer considered a disease that affects only white middle-class boys, as eating disorders are no longer responsible only for white middle-class girls.
Yet he warned against overdiagnosing ADHD in cases where behavioral problems could be caused by social or environmental factors such as overcrowded classrooms.
The study found that the incidence of ADHD among girls rose from 3 to over 6 percent. It said that this was partly a consequence of the change in the classification of the condition. For years, ADHD had involved children who were hyperactive. But in recent years, the American Psychiatric Association has added to their mental health guide conditions that diagnosis should also include some infants who are inattentive, Bao said. That has increased the number of girls, he explained, because they seem to be more in this second subtype.
"If you compare these two, you can easily imagine that people can easily recognize hyperactivity," he said . That was true for Ruth Hay, a 25-year-old New York-born student and cook who is now in Jerusalem lives. She was diagnosed with what was then called ADD the summer between the second and third grade.
Hay said her hyperactive tendencies are not as "loud" as some people's. She is less likely to jump around in a room than to hop in her chair, she said.
Despite her early diagnosis, Hay said, nobody told her about other symptoms. For example, she said, she suffers from executive dysfunction, which makes her feel unable to perform tasks, no matter how much she wanted or tried.
"I've been called lazy in times when I was not lazy," said Hay. "If you look at a list of all the different symptoms of ADHD, I have them all to one degree or another, but the only ones that have ever been discussed with me are that you may be less focused and fidgety."
"I do not know what my brain would be like if I did not have it," she added. "I do not know if I'm still me, but all that was for me is a disability."