Why Childhood ADHD Estimates Worldwide Differ Significantly
(HealthDay News) — About 7% of children worldwide have attention-deficit/hyperactivity disorder (ADHD), new research concludes. The study was published online March 3 in Pediatrics.
The estimate comes in lower than the latest data from the U.S. Centers for Disease Control and Prevention, which reports that 11% of U.S. school-age children had been diagnosed with ADHD by 2011. However, it is double a worldwide ADHD estimate of 3.4% published in the Journal of Child Psychology and Psychiatry earlier this year.
In the new study, researchers examined decades' worth of research on ADHD and came up with 175 studies containing 179 estimates of ADHD prevalence. When pooled together, the combined results contained data on more than one million children over a period of 36 years. The studies took place in North America and Europe. All the data added up to a worldwide ADHD estimate of 7.2%, with a range running from 6.7 to 7.8%, according to the report. The lead author Rae Thomas, BEd, PhD, of Bond University in Robina, Australia, told HealthDay that the estimate did vary between versions of the Diagnostic and Statistical Manual of Mental Disorders (DSM) -- studies based on the DSM-IV had an average prevalence of 7.7%, while the DSM-III-based studies estimated 5.6% and the DSM-IIIR estimated 4.7%. The included studies also varied widely in their estimates of ADHD, from a low of 0.2% to a high of 34%, she said.
Critics say there may be serious problems with the way the team came to their conclusions, noting the research pools together dozens of studies that used a wide variety of criteria to determine whether children had ADHD.