A post here at Psychology Today created real interest in the possibility that French children may be less likely to be diagnosed and treated for Attention Deficit Hyperactivity Disorder. In fact, however, the prevalence of ADHD among French children appears to be about 3.5% to 5.6% - which is consistent with the DSM-IV-TR estimate of prevalence in the US. And, just as in the US, the diagnosis was frequently co-occurring with behavioral disorders and academic underperformance, and boys were more likely than girls to receive a diagnosis of ADHD.
Likewise, a 2003 literature review found similar prevalence of ADHD in 30 non-US countries.
Among adults, estimates of ADHD appeared to vary from about 2% to 4% in this 2007 study across 10 nations. Those numbers are consistent with a pooled prevalence estimate of 2.5% in this 2009 meta-analysis.
A study published just a couple of weeks ago found comparable demographics and baseline characteristics among adults with ADHD across European and non-European samples and concluded that ADHD research conducted outside the regions is likely generalizable to European patients.
So the evidence suggests that French kids, as well as children and adults from other nations, do in fact experience the functional (school, social, work, time-management) challenges of ADHD.
Rather than international variability of ADHD diganosis, the real shocker (to me, at least, and to attendees at my workshops) is the state-by-state variability of children diagnosed and treated for the condition. Check out this helpful article from the CDC (scroll down a bit to the blue map of the US). What thoughts or questions come to mind for you? Do you detect an East-West distinction? And among Eastern states, what patterns do you notice, and how do we account for those differences? Surely we don't think that 6% of kids in Texas "have" ADHD while just next door in Louisiana the prevalence is 15%, right?
As we think of this variability within the US, we almost certainly conclude that some of that difference is over-diagnosis. And there are negative consequences with "finding" ADHD when it's not there. But the implications for "missing" it - for underdiagnosing the disorder - are also significant.
The best evidence points to this: ADHD is not a US phenomenon. And when we find meaningful variability across populations, the questions which might come to mind include:
- are clinicians using different criteria, or understanding diagnostic criteria differently?
- are there social or economic pressures which lead to variability across populations?
- are there specific supports which protect and buffer the functional impact of ADHD symptoms among individuals in some groups?
Because ADHD is a disorder of performance rather than ability, we expect to find variability across settings and tasks. That variability is instructive: "What about this task or this setting is such a good match for this individual? And how can we make other areas of his/her life more like that?"
But the nature of the disorder is not such that we should see variability across state lines or national boundaries. Those differences probably tell us less about the brain-based condition itself and more about our diagnostic tools and strategies and accuracy.