From the late 1980s to the early 2000s, the rate of diagnosis of Attention Deficit Hyperactivity Disorder (ADHD) soared 500 percent. Today 5 to 10 percent of all U.S. children between the ages of 6 and 18 have been diagnosed with ADHD.
A recent study by University of Notre Dame economist William Evans and colleagues at the University of Minnesota and North Carolina State University suggests that, at least in part, the epidemic may be driven by misdiagnosis. The economists reach that conclusion based on statistical analyses of data on ADHD diagnosis, medication treatment and the age of those diagnosed relative to peers enrolled in school. The study will be published in an upcoming issue of the Journal of Health Economics.
The researchers discovered that children who are “older for their grade” are less frequently diagnosed and treated for ADHD. Children born just after the cutoff date for enrollment and therefore relatively old for their grade had a significantly lower incidence of ADHD diagnosis and treatment than classmates born just before the cutoff and, therefore, young for their grade. All things being equal, such a disparity should not exist. The fact that it does suggests something other than the disorder is causing the increase in diagnosis.
Evans and his colleagues conclude that some children may be mistakenly diagnosed with ADHD because they exhibit more immature behavior than older classmates. The researchers note that diagnosing ADHD is difficult. Children who have the disorder are hyperactive, have a difficult time staying focused and act impulsively, but even non-ADHD children occasionally exhibit such behavior. For those truly having the disorder, however, the behaviors are pervasive and persist into adulthood.
According to the economists’ analysis, approximately 1.1 million children may have received an inappropriate diagnosis and more than 800,000 received stimulant medication due only to relative maturity.
The Keough-Hesburgh Professor of Economics, Evans’ work focuses on social issues and the policies used to address them. His research is regularly cited in other disciplines, including medicine, health care finance and public health.