In The Politics of Autism, I discuss the uncertainty surrounding estimates of autism prevalence.
Dr. Allen Frances, the lead editor of previous version of the manual, says that the diagnostic instructions are confusing, so the diagnosis will vary from rater to rater and place to place. “It will be even more impossible than it is now to determine rates of autism and why they shift so much over time.” A more recent study says that prevalence estimates are likely to decline under DSM-5 – but it cautions that policies for service eligibility and diagnostic tools will change in response to the revised criteria. Clinicians may react by looking for more symptoms to back up ASD diagnoses.
And DSM-5 is not the last word. Whereas the titles of previous editions included Roman numerals (DSM-III, DSM-IV), the new one instead has an Arabic numeral to make it easier to designate revisions. The future will bring DSM-5.1, DSM-5.2, and so on, which may include further changes in the way we describe and diagnose autism.
The rapid rise in autism cases is not because of vaccines or environmental toxins, but rather is the result of changes in the way that autism is defined and assessed — changes that I helped put into place.
In the late 1980s and early 1990s, I chaired the task force charged with creating the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders, or the D.S.M.-IV. Sometimes called the “bible of psychiatry,” the D.S.M. influences medical practice, insurance coverage, education and treatment selection.
In the third edition of the D.S.M., published in 1980, autism was tightly defined and considered extremely rare. Criteria for the diagnosis required a very early onset (before age 3) of severe cognitive, interpersonal, emotional and behavioral problems.
But my task force approved the inclusion of the new diagnosis, Asperger’s disorder, which is much milder in severity than classic autism and much more common. In doing so, we were responding to child psychiatrists’ and pediatricians’ concerns for children who did not meet the extremely stringent criteria for classic autism, but had similar symptoms in milder form and might benefit from services.
Based on careful studies, our task force predicted that the addition of Asperger’s disorder would modestly increase the rate of children given an autism-related diagnosis. Instead, the rate increased more than 16-fold, to one in 150 from an estimated one in 2,500 in the span of a decade. It has been climbing more gradually ever since and is one in 31 today. Our intentions were good, but we underestimated the enormous unintended consequences of adding the new diagnosis.
The resulting explosion in cases included many instances of overdiagnosis — children were labeled with a serious condition for challenges that would better be viewed as a variation of normal. It also sowed the seeds of conspiracy theories and anti-vaccine beliefs as people wondered how to explain the rising cases.
Many large studies have come to the same conclusion: Vaccines don’t cause autism. The role, if any, of environmental toxins is still to be determined, but there is no known environmental factor that can explain the sudden jump in diagnoses. The changes we made to the diagnosis in the D.S.M.-IV can.
Why did autism-related diagnoses explode so far beyond what our task force had predicted? Two reasons. First, many school systems provide much more intensive services to children with the diagnosis of autism. While these services are extremely important for many children, whenever having a diagnosis carries a benefit, it will be overused. Second, overdiagnosis can happen whenever there’s a blurry line between normal behavior and disorder, or when symptoms overlap with other conditions. Classic severe autism had so tight a definition it was hard to confuse it with anything else; Asperger’s was easily confused with other mental disorders or with normal social avoidance and eccentricity. (We also, regrettably, named the condition after Hans Asperger, one of the first people to describe it, not realizing until later that he had collaborated with the Nazis.)
