Why Is Autism So Prevalent Now?

One of the things that has proven most shocking about the epidemic of Autism Spectrum Disorder (ASD) diagnoses in the United States has been the suddenness with which it swept the country. In the span of a single generation, from 1985 to 2015, cases skyrocketed from 1 in every 2500 to 1 in every 65. Just from 1993 to 2003, the numbers jumped by 657 percent, according to the Scientific American.

For families whose lives have been affected by ASD to the medical professionals and applied behavior analysts who treat the condition, the explosion has been shocking, particularly because we still have no real understanding of the cause behind it.

The desperate search for answers has lead people down some strange and occasionally harmful roads. The suggestion from one small and later discredited study in England that MMR (Measles, mumps, and rubella) vaccinations given in childhood were a possible cause for the skyrocketing numbers was enough to set off the whole anti-vaxxer movement… a trend of withholding common vaccinations from children that has contributed to upticks in whooping cough and measles outbreaks in the U.S. and U.K.—without any decrease in ASD diagnoses.

So the one question on everyone’s mind is why does autism – a disorder that was first described in the 1940s – seem to be so common now?

The Epidemic That Never Was: Autism Has Always Been With Us

But the truth may be both stranger and more prosaic: there may be no epidemic at all.

To understand why, you have to plumb some of the hard questions about what autism actually is, and how we have come to view the disorder since it was first defined in the 1940s.

A psychiatrist at Johns Hopkins named Leo Kanner was the first doctor to describe the condition as a distinct disorder in 1943. But Kanner didn’t coin the term; similar symptoms had been described as autistic as early as 1910, and accounts from as far back as the 18th century describe patients who, in all likelihood, would have fit modern standards for an ASD diagnosis.

So autism has always been with us and in proportions that have not always been clear. Inventing a diagnosis did not invent the disorder. And it turns out to be very likely that changing the diagnostic routines has not actually changed the number of people afflicted, but only our ability to accurately count them.

That change happened in 1994. The Diagnostic and Statistical Manual of Psychiatric Disorders, the standard classification system used by psychiatrists, had provided a diagnosis for autism since 1980. That diagnosis required that candidates match six of six possible criteria—a high standard. But the new version of the DSM released in 1994 required that only eight of sixteen criteria be met—a lower bar.

At the same time, other societal pressures may have contributed to an increase in ASD headcount. As a Scientific American article from 2012 points out, the passage of the IDEA (Individuals with Disabilities Education Act) in 1990 began to require that school districts report a precise headcount of students with disabilities. That produced a surge in easily-accessible numbers that have been easier to calculate and report than the population-based models favored by epidemiological researchers.

Finally, as autism came to be better described and understood, it lost many of the social stigmas of other childhood psychiatric conditions. Because the disorder exists along a spectrum that can be accommodated in many circumstances and because applied behavior analysis offers effective treatment for many patients, an autism diagnosis has become less onerous over the years. More parents recognize the symptoms and refer their children to screening.

So not only was the community becoming more familiar with and adept at recognizing the disorder, but it was happening during a period when there was more and more pressure on them to make such diagnoses.

One sign that this is behind the growth can be found by comparing the increase in autism diagnoses to those of other intellectual disabilities. Since 2000, the two have tracked on almost an exact inverse—suggesting that perhaps autistic children who were being classified with other disabilities are now being given the proper classification.

In fact, a 2015 study in Denmark attributed about 60 percent of the increase in autism diagnosis to DSM changes alone.

Of course, if the dramatic rise really is attributable largely to diagnostic changes, you would expect to see that factor as a one-time increase in the numbers. Although not instantaneous, due to both awareness and adoption rates that vary across the country, there is some indication that this is exactly what has happened in the United States. The latest CDC numbers, released in 2015, show that the incidence rate had largely leveled off: between 2010 and 2012, the rate stayed static at 1 in 68.

This is good news for ABAs. Since applied behavior analysis is one of the few treatments for autism scientifically proven to be effective, it means more children will be getting the kind of treatment they need for their disorder. Although the surge of attention that has accompanied the reporting of the autism epidemic may have been misplaced, it has also focused much-needed funding and resources on a disorder that previously received too little attention.