Changes in disability laws
When the Individuals with Disabilities Education Act (IDEA) was reauthorized in 1991, ADHD was for the first time included specifically as a type of disability that gained patients special accommodations. At nearly the same time, Medicaid reimbursements began to include ADHD. Rates of ADHD diagnosis throughout the U.S. rose rapidly through the 1990s, presumably in part because of these legal and policy changes. Apparently, as parents and physicians learned that the ADHD label allowed more mandated services, pressures to apply that diagnosis increased.
Unintended consequences of No Child Left Behind policies
One of the more interesting sources of inflated ADHD rates is related to a series of policies designed to improve test scores and graduation rates in U.S. schools. We were led to this research by another striking ADHD prevalence finding that emerged from the NSCH. Although the main observation has been an inexorable rise in national ADHD prevalence rates, the NSCH also uncovered a huge state-by-state variation in diagnosed prevalence. The highest rates are in the South and Midwest; the lowest are in the West. Significant variations in disease rates in different states provide a “natural experiment” in the attempt to isolate factors that might lead to artificially inflated (or deflated) rates of diagnosis.
Our research method was to study in detail two highly contrasting states: North Carolina, which had a 2007 ADHD prevalence of 15.5% (and a medication rate of 74.4% of those diagnosed), vs. California, with a prevalence of only 6% (medication rate of 49%).
What explains this large difference? A small part relates to racial and ethnic diversity. For example, 49% of the CDC’s California sample was Hispanic, vs. only 9% of the North Carolina sample. Other research has shown that Hispanics are less likely to be diagnosed with ADHD than other ethnicities—so a state with a relatively large population of Hispanics might have a lower ADHD prevalence in part due to ethnic variation. However, when we statistically controlled for differences in ethnic composition, there was still a far greater prevalence in North Carolina.
The more important difference between the two states, by far, turns out to relate to school improvement initiatives such as the No Child Left Behind Act (NCLB). Such policies differ in specifics, but their common feature is their provision of financial incentives for schools to improve student performance (usually measured by test scores), as well as financial sanctions for schools that do poorly.
How might such policies lead to inflated rates of ADHD? There are at least two mechanisms. First, in some regions, the test scores of children with ADHD were not included in the test score averages that schools must report to their state. Thus, if low-scoring students can get an ADHD diagnosis, a school enriches its pool of test-taking students with high scorers—leading potentially to rewards to the school for performance improvement. Second, even in school districts that do count test scores of ADHD students, there is still an incentive to encourage diagnosis. Recall that the 1991 IDEA law enabled kids with ADHD to be eligible for special educational accommodations, such as more time for test-taking. If such accommodations help to improve test scores, then schools would have a strong incentive to ensure that ADHD diagnoses are not missed.
To see whether NCLB policies had the unintended effect of increasing ADHD diagnoses, we compared prevalence rates before and after NCLB was implemented. We found that, as predicted, NCLB had a profound effect on rates of ADHD—but only for youth near or below the federal poverty level (the law targets Title I schools with many low-income students). From 2003 (when NCLB was implemented) to 2007, rates of ADHD for impoverished youth increased from 10% to 15.3% in those states where NCLB was new—an increase of over 50%. In states that already had implemented their own versions of NCLB before 2003, however, there was no corresponding increase in ADHD rates, which makes sense, because the diagnosis inflation effect of the policy would have already occurred in such states (for more detail, see Fulton BF et al, Psychiatric Services 2015;66(10):1074–1082).
In our book, we discuss other factors that may contribute to inflated ADHD rates, but are less easy to quantify. One of these is the increasing aggressiveness of pharmaceutical marketing practices, including direct-to-consumer advertising and industry-funded direct promotion to doctors. Another potential factor is that clinicians do not always follow gold-standard guidelines for careful diagnostic evaluations, which, although time-consuming, can often find that apparent ADHD symptoms are actually caused by other problems, such as poor family environments or comorbid conditions. Finally, ADHD is often diagnosed by busy primary care physicians who may not have the time or the expertise to delve into the nuances of diagnosis.
In sum, while ADHD is a legitimate and disabling condition for many people, a number of social, political, and economic factors have combined to artificially inflate its reported prevalence in the U.S. The unfortunate consequence is that, at least in some quarters, ADHD has acquired a reputation of being a trivial and possibly manufactured disorder—potentially fueling its stigmatization. Being more cautious in our policy decisions and in our diagnostic practices will help to improve the public’s confidence in our field.