The number of children in the United States diagnosed with Attention Deficit/Hyperactivity Disorder (ADHD) increased from 6.1 percent to 10.2 percent from 1997 to 2016, according to an analysis from the University of Iowa published in the Journal of the American Medical Association (JAMA) Network Open.
This upward trend cut across all demographic subgroups, says Wei Bao, assistant professor of epidemiology in the UI College of Public Health and study co-author.
“Our findings indicate a continuous increase in the prevalence of diagnosed ADHD among U.S. children and adolescents,” says Bao.
The study analyzed the health information of more than 186,000 children and adolescents gathered by the U.S. National Health Interview Survey (NHIS), an annual survey of American households conducted by the U.S. Centers for Disease Control and Prevention. The data were collected annually from 1997 to 2016.
The analysis found that 1,243 children age 4 to 17 were reported to have ADHD in the 1997–98 survey, representing 6.1 percent of U.S. children and adolescents. That increased to 1,880 reported cases in 2015–16, representing 10.2 percent of U.S. children and adolescents.
The analysis also found this upward trend across gender, racial, family, and geographic lines. However, it found that not all increases were uniform, and that there were distinct differences within groups.
For instance, in the gender subgroup, the research showed 14 percent of boys were diagnosed with ADHD in 2016, up from 9 percent in 1997. However, only 6.3 percent of girls were diagnosed with ADHD in 2016, up from 3.1 percent in the 1997 survey.
While the number of Hispanic children diagnosed with ADHD jumped from 3.6 percent to 6.1 percent, they are still far less likely to receive a diagnosis than children from other racial groups. White children in the survey were diagnosed with ADHD at a 12 percent rate in 2016, up from 7.2 percent in 1997; 12.8 percent of African American children were diagnosed with ADHD in 2016, up from 4.7 percent in 1997.
The survey also found incidences of the disorder varied significantly by geography. Children in the Western region of the United States were less likely to be diagnosed with ADHD—7 percent in 2016—compared to the Northeast, Midwest, or South, all of which exceeded 10 percent. In 1997, 5 percent of children in the Western states were diagnosed with ADHD, while other regions ranged from 5.5 percent to 6.9 percent.
The NHIS survey did not attempt to find a cause for the increase, but the authors offered some possible factors, such as increased awareness of ADHD and a diminished social stigma for ADHD. Changes that expanded the definition of the disease also may have contributed to the increase.
They say that previous studies also support a role of environmental risk factors, such as exposure to lead or certain pesticides or chemicals during pregnancy and the postnatal period, as well as nutritional deficiencies. Prenatal and perinatal risk factors, including pre-term birth, low birth weight, maternal cigarette smoking, and use of certain medications or illicit substances during pregnancy also have been associated with ADHD risk in previous studies.
The study, “Twenty-year trends in diagnosed attention deficit/hyperactivity disorder among US children and adolescents, 1997–2016,” was published in the Aug. 31 issue of JAMA Network Open. It was first-authored by Guifeng Xu in the UI College of Public Health and co-authored by Lane Strathearn of the UI Roy J. and Lucille A. Carver College of Medicine, Buyun Liu of the UI College of Public Health, and Binrang Yang of Shenzhen Children’s Hospital in China.
The study can be found online at the JAMA Network Open website.