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Description: Think about this logically. If the incidence of a diagnostic category within the DSM in the general population shows a big jump what sorts of explanations might we begin to look for to account for it? Well, in the United States, and in Canada as well, the rate of ADHD within the child population has jumped upwards dramatically since the turn-of-the-century. Why might that be?

Source: ADHD diagnoses soar 43% in United States, Yahoo parenting, Kerry Sheridan.

Date: December 9, 2015


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Links: Article Link —

Epidemiologists are researchers who study the incidence or rates of particular illnesses or disorders in the general population and the factors which influence those rates. Epidemiologists are particularly interested when the incidence of a particular disorder shows a rapid increase or decrease. They are interested because such changes in incidents or rate suggest that something else that is potentially causally relevant to the disorder or disease has also changed. So, for example, the huge jump in birth defects and other issues that arose in the area surrounding Chernobyl after the nuclear meltdown there in 1986 unfortunately told us a great deal about the effects of exposure to radiation on developing fetuses and embryos. So, it may well be that there are new environmental or social factors at work which are causally linked to the observed dramatic increases in diagnoses of ADHD within North America. However, it may also mean that there’s been a shift in how ADHD is defined or in both public and professional awareness of the disorder and its range of manifestations. The article discussed in the media post to which this blog refers looks most closely at the increasing incidence itself but offers us an opportunity to speculate about some of the things that may be behind it and to also think about what kind of research we might need to do to sort out precisely what is going on.

Questions for Discussion:

  1. What are some of the possible environmental or psychosocial explanations for why the rate of ADHD might have increased since the year 2000?
  2. What are some of the alternative explanations for why the rate of diagnosis of ADHD may have increased even if the actual underlying prevalence of the disorder may not have shifted?
  3. What sorts of studies might we need to do to sort out the contributions that you outlined in response to the first and second questions above in our thinking and in our policy and intervention planning related to ADHD?

References (Read Further):

Collins, K. P., & Cleary, S. D. (2015). Racial and Ethnic Disparities in Parent-Reported Diagnosis of ADHD: National Survey of Children’s Health (2003, 2007, and 2011) (No. b058db857503494eb1ca293fa48caa2d). Mathematica Policy Research.


One Response to “ADHD Incidence Jump: Think Like an Epidemiologist”

  1. Mark Speechley

    This is excellent. I’ve taught epidemiology for many years and this is a perfect example of the distinction between ‘real causal’ hypotheses (the interesting, exciting ones that everyone wants to test) and ‘artifactual’ hypotheses that many people find boring, but are absolutely essential to test before we move to the fun stuff.

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