ADHD News & Research

Just How Common Is ADHD, Really? A New Study May Have the Answer

The rate of ADHD worldwide has been disputed for years. Now, researchers may have identified the benchmark rate of ADHD, to help medical professionals determine whether communities are being over-diagnosed or under-diagnosed.

March 16, 2015

For as long as ADHD has been recognized by the medical community, the rate at which it occurs in children has been disputed, ranging from as low as 3 percent to as high as 14 percent. The conflicting numbers confuse parents, doctors, and patients, who struggle to determine if the condition is over-diagnosed — and over-medicated — or under-diagnosed.

A new study published in Pediatrics claims to have identified a benchmark estimate for the worldwide rate of ADHD in children. The study’s authors analyzed the data from 175 studies from around the world, conducted over 36 years, to reach their overall estimate: approximately 7.2 percent of children worldwide have ADHD.

By using this rate as a benchmark, the authors say, medical professionals can begin to determine if over- or under-diagnosis of ADHD has occurred in their community. Though a majority of the studies were done in Europe and North America, the total number of studies analyzed was spread evenly enough around the world that the researchers are confident in their conclusion.

Since the Diagnostic and Statistical Manual of Mental Disorders (DSM) has been revised several times over the years, the researchers also looked at whether the rate of ADHD diagnosis had changed along with the DSM. Since the DSM-IV has an updated (and perhaps — as some critics argue — looser) definition of ADHD, researchers expected to see a significant increase in diagnoses as the DSM-IV was widely used. However, no statistically significant difference was seen between the DSM-III and the DSM-IV criteria, researchers said.

The 7.2 percent estimate is lower than the most recent data from the U.S. Center for Disease Control and Prevention (CDC). It claims that 11 percent of school-aged children have ADHD. However, since this study looked at a worldwide population — not just the United States — it’s possible that the jump in U.S. diagnoses may be related to other contributing factors, researchers said.

The study, while comprehensive, does have some concerns. Most of the individual studies (74 percent) looked only at school populations, possibly excluding children who were homeschooled or otherwise outside the school population. In addition, the individual studies were primarily focused on specific communities or regions, which limits the ability of researchers to use them to form generalities about the global population.

Despite the concerns, however, the researchers believe the study to be a major step forward in eliminating ADHD stigma and helping those who are affected get the treatment they need. “Media reports of high rates of diagnosis may cause suspicion regarding the diagnosis overall,” said Rae Thomas, Ph.D., the lead researcher on the study. But “an accurate diagnosis is arguably the single most important thing a clinician can do for a patient.” These new estimates, he concludes, may give clinicians more accurate tools to use when searching for a diagnosis.