It's a very common claim that ADHD is over diagnosed, or even doesn't exist; and in particular I've heard claims that AD/HD is over diagnosed within the US since it's diagnosed more often in the US then in some other countries.

I'm trying to determine if this is true, to the best of our ability; which admittedly is very difficult. Assuming we accept AD/HD exists as a disorder which can and should be treated in some individuals can anyone provide studies which could indicate the likely level of over diagnoses within the US. Actually, to be more exact can anyone point to studies on number/percentage of individuals likely to have been misdiagnosed with AD/HD when they do not have it; or how those rates of false diagnosed as AD/HD may compare to other nations.

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    How would you know if someone was properly diagnosed or not? You would have to have a definition of what AD/HD is and then have experts diagnose people as either having it or not. The problem is that is literally what we do now to diagnose it in the first place. – Kevin Wells Feb 12 '16 at 22:16
  • Anyone know if SPECT imaging (measuring blood flow to certain brain structures) has held up as a diagnostic tool for ADD/ADHD? That information would tell us a lot about the "even exists" portion. – PoloHoleSet Nov 20 '17 at 18:10
  • Note that "overdiagnosed" doesn't quite mean what people think it means. It is entirely possible to over- and underdiagnose something at the same time. – Tgr Nov 21 '17 at 11:40

This is a difficult question for several reasons:

From a WebMD article:

Some say the disorder is a modern problem, one that "didn't exist" when your parents and grandparents were growing up. People point to the fact that the number of American children 4-17 who've been diagnosed with ADHD increased 42% between 2003 and 2011. But does that mean more people have the condition than ever before? Again, the facts are a bit murky.

[Mandi Silverman, PsyD, a clinical psychologist at the ADHD and Disruptive Behavior Disorders Center at the Child Mind Institute replies:] "Our answer is that there's more awareness, more research, and we have more sophisticated assessment tools."

There's also significant variation even within the US; from the same aritcle:

Another ADHD-related mystery is that rates seem to vary a lot based on geography. More than 13% of children in certain states -- including Alabama, Arkansas, Kentucky, Ohio, Rhode Island, and South Carolina -- have been diagnosed with the disorder. Yet other states -- including California, Colorado, and Nevada -- report diagnosis rates of 7% or lower.

There are also big differences in the number of people who are diagnosed with ADHD around the world. For example, some surveys have found that 11% of children in Australia have been diagnosed, compared to less than 3% in the United Kingdom.

Since in the US the criteria are the same, the difference can only come from training differences of the mental health professionals applying the diagnosis and/or variation in the pool of children that are screened in the first place... The CDC has some potential insight into the latter, with racial and insurance variation:

In 2011–2013, the prevalence of diagnosed ADHD among children aged 4–17 was 11.5% among non-Hispanic white children, 8.9% among non-Hispanic black children, and 6.3% among Hispanic children.

In 2011–2013, the prevalence of diagnosed ADHD among children aged 4–17 was highest among children with public insurance (11.7%) and lowest among uninsured children (5.7%). Among children with private insurance, the prevalence of diagnosed ADHD was 8.6%.

An intriguing explanation of the geographic varioation within the US is found in a 2013 NYT article:

Even after [Stephen] Hinshaw’s team accounted for differences like race and income, they still found that kids in North Carolina were nearly twice as likely to be given diagnoses of A.D.H.D. as those in California. [...] In trying to narrow down what those influences might be, Hinshaw evaluated differences between diagnostic tools, types of health insurance, cultural values and public perceptions of mental illness. Nothing seemed to explain the difference — until he looked at educational policies.

The No Child Left Behind Act, signed into law by President George W. Bush, was the first federal effort to link school financing to standardized-test performance. But various states had been slowly rolling out similar policies for the last three decades. North Carolina was one of the first to adopt such a program; California was one of the last. The correlations between the implementation of these laws and the rates of A.D.H.D. diagnosis matched on a regional scale as well. When Hinshaw compared the rollout of these school policies with incidences of A.D.H.D., he found that when a state passed laws punishing or rewarding schools for their standardized-test scores, A.D.H.D. diagnoses in that state would increase not long afterward. Nationwide, the rates of A.D.H.D. diagnosis increased by 22 percent in the first four years after No Child Left Behind was implemented.

The WebMD article also claims that

A recent review of studies concluded that the true rate of ADHD among children is pretty similar throughout Asia, Africa, Australia, Europe, and the Americas.

without a clear reference, so I'm guessing it might be pointing to the highly cited (>1500 in GS) 2003 review of Faraone et al.. Here's the summary of findings (keep in mind that it predated DSM-5):

enter image description here

​Table 7 shows the range of prevalence rates for US and non-US populations for the three DSM diagnostic criteria when outlying values have been excluded. Comparison of the prevalence range for the US studies shows that the highest prevalence is reported when using DSM-IV criteria, as has previously been shown by Wolraich et al (17) and Baumgaertel et al (16). The non-US studies also showed a higher prevalence of ADHD when using DSM-IV diagnoses. As ​Table 7 shows, the range of prevalence reported in the non-US studies is, for each diagnostic system, similar to that reported in the US studies.

Several of the non-US DSM-III-R and DSM-IV studies found fairly low prevalence figures, between 2.4 and 7.5%. The countries included in the low-prevalence group are Sweden (2/2 studies in this population), Italy (1/1 study in this population), Australia (2/2 studies in this population), Iceland (1/1 study in this population), and Spain (1/1 study, but only for 11 years age group). This may reflect a true lower prevalence in these countries but further studies are required to confirm this. These countries are not represented in the studies using DSM-III diagnostic criteria.

Whether this exclusion is cherry picking or justifiable removal of outliers... you be the judge. The review does confirm the obvious fact that the more inclusionary the criteria is, the more children get diagnosed, regardless where they live.

A slightly more recent (2007) and even more highly cited review (>3K in GS) concludes with

geographic location plays a limited role in the reasons for the large variability of ADHD/HD prevalence estimates worldwide. Instead, this variability seems to be explained primarily by the methodological characteristics of studies

And exactly what was found to influence the results is summarized in the regression table below:

enter image description here

And here's the authors' explanation in words

In the final multivariate metaregression model (Table 2), the methodological variables that remained significantly associated with the prevalence rates were the requirement of impairment for the diagnosis, diagnostic criteria, and source of information. As expected, studies without a definition of impairment had significantly higher ADHD/HD prevalence rates than those with a definition of impairment (p<0.001). Studies based on DSM-III-R or ICD-10 criteria, respectively, had significantly lower ADHD/HD prevalence rates than those using DSM-IV criteria (p=0.02 and p=0.005, respectively). Studies that relied on information provided by parents, teachers, and “or rule,” respectively, were associated with significantly higher ADHD/HD prevalence rates than those relying on a best-estimate procedure (p=0.02, p<0.001, and p=0.003, respectively), whereas those relying on information provided using the “and rule” criterion were associated with significantly lower ADHD/ HD prevalence estimates (p=0.04) (Table 2). Geographic location was associated with significant variability between estimates from North America and both Africa (p=0.03) and the Middle East (p=0.01). Estimates from these areas were significantly lower than estimates from North America. No significant differences were found in prevalence rates between North America and Europe (p=0.40), South America (p=0.83), Asia (p= 0.85), or Oceania (p=0.45) (Table 2). The multivariate metaregression model using Europe for the comparison yielded similar findings. Impairment, diagnostic criteria, and source of information remained significantly associated with prevalence rates. Significant differences were found only between Europe and both Africa (p=0.05) and the Middle East (p=0.03).

To increase power by decreasing degrees of freedom, an additional model was run using only methodological variables initially. Methodological variables associated with the prevalence rate for a p≤0.20 in univariate analyses were initially included and progressively deleted from the model using a backward procedure. Then, the geographic location of the studies was entered. In this multivariate model, geographic location was not significantly associated with prevalence rates after adjustment for methodological variables (data available from authors upon request). Finally, since most studies were conducted in Europe and North America (N=64), the same data analysis strategy was applied using only these two regions. In the final multivariate metaregression model, the same methodological variables remained significantly associated with prevalence rates: impairment, diagnostic criteria, and source of information. Again, geographical location (Europe versus North America) was not significantly associated with ADHD/HD prevalence rates (p=0.61).

It's notable that, in contrast, if you simply look at the prevalence rates geographically without taking into account all the other variables, there does seem to be an explanatory difference between Europe and North America.

enter image description here

However this difference was better explained (in the authors' regression analysis) by the methodology used rather than by geography. The (sparse) data from Africa and the middle East however could not explained away by methodological variables alone. Hence the conclusion of the study that "geographic location plays a limited role".

One more thing to note is that some environmental/developmental factors affecting ADHD are known, in particular prenatal exposure to tobacco smoke. So potentially such factors could explain some/more of the geographic variation as well, although whether they do, I don't know.

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    One thing to note, with regard to geographic variations, is that ADHD is highly heritable. – Daniel R Hicks Nov 20 '17 at 18:54

Yes - Because of No Child Left Behind.

From the APA's website:

What, specifically, did you find out about the effect of these education policies?

Hinshaw: Thirty states, including all of the Southern states, passed these accountability laws before the No Child Left Behind Act — which, like the state consequential accountability laws, sets standards and establishes measurable goals in an effort to improve education outcomes for students — went into effect in 2002, so we were able to compare those 30 states to the other 20 before and after it became federal law to have consequential accountability. What we found was that standards-based education reform had likely played a large role in the nation's huge increase in ADHD diagnoses. Between 2003 and 2007, in those 20 states that didn't get consequential accountability until No Child Left Behind was implemented, we found a 59 percent increase in ADHD diagnoses among children who were within 200 percent of the federal poverty limit — so among the poorest kids in the state. Among middle- or upper-class kids in those states, there was only a 3 percent increase in ADHD diagnosis. That's a huge and statistically significant difference. But in states that had already passed the accountability laws before No Child Left Behind, rates of ADHD diagnosis only went up 20 percent, which is pretty much the national average, and there was no difference between poor and rich kids. Are we saying that consequential accountability is the cause? No. But there's a really strong association, and it's almost a smoking gun that when test scores really, really count in the public schools, for the poorest kids in a state, ADHD diagnoses go up dramatically shortly thereafter. What's the sum total of this? School policies really seem to matter, in a way that factors such as ethnicity, medical professionals and culture don't. Can we say they're the absolute and only cause of these state and regional differences? No, but they sure seem to be implicated.

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    You haven't shown it is over-diagnosed. Just that it is diagnosed more where there are incentives for recognising it. – Oddthinking Nov 20 '17 at 22:36
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    without trying to be pedantic, "diagnosed more where there are incentives for recognising it" sounds the same as over-diagnosed to me – Felipe Nov 22 '17 at 21:16
  • -1, because schools don't diagnose ADHD. Sure diagnoses become more common when schools start recommending that students get checked out, but that doesn't imply "over-diagnosed". In fact, we might interpret this as suggesting that, before such efforts, it was under-diagnosed. (Though that's not necessarily true, either.) – Nat Nov 27 '17 at 4:02

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