The diagnosis of autism has only been with us for about 70 years when it was first identified by Leo Kanner. That’s not very long. But most likely, people with autism have always been around. Prior to Kanner’s study, those with autism, depending on the severity, were either not clinically noticed, were referred to as being “off” or “different,” or diagnosed as schizophrenic or insane. Later on some would also fall under the diagnosis of mental retardation. We’ve come a long way in addressing the specific characteristics and needs of autistic children.
The data sets that are frequently used to support the “autism epidemic” argument are often misunderstood or misinterpreted. Take, for example, what is the oft referred to “California Data.” There are many reasons to be cautious with this data. In 2002 the University of California completed their MIND study (The California Data) which had been commissioned by the California legislature. This study rose out of reasonable concern over what appeared to be a 273% increase in rates of autism. Their conclusion was that the broadening of the diagnostic criteria did not impact the rapidly rising rates.
So what was wrong with their study? They studied 2 cohorts of children with autism born in 1983-85 and 1993-95. Both groups were assessed with the same instrument (a data collecting interview), however the instrument was based on the later DSM-IV which hadn’t been around in the early 1980s and was much more inclusive. For that reason, all the children from the first cohort met the criteria as did all the children of the second. The researchers then erroneously concluded broadening the diagnosis didn’t make a difference. Complicated right? Had they reversed it and used the DSM-III criteria for both groups, then there most likely would not have been such a drastic increase.
Let’s use weight as an example to make this a little clearer. Let’s say that in the 1980s children weighing less than 35 pounds at age 4 were considered underweight (regardless of height). Then in the 1990s we changed the criteria and say all 4-year-olds under 45 pounds are considered underweight. Would all the underweight children from the ‘80s be included in this new definition? Yes. Would there also be a significant number of children added to the underweight category by the 1990s definition? Of course. Has the actual number of underweight children increased? Depends on how you look at it. This is broadening of a diagnostic criteria.
Another data set that appears to show drastic rates of increase is the Individuals with Disabilities Education Act (IDEA) data. This is sometimes called the “Child Count” data.
A child diagnosed with autism under IDEA receives additional free education services. For some families this is an absolute godsend. Every year the Federal Government requires reporting of the number of children served by this act. This is where you will see people pulling the numbers like a 1,354% increase. The period of time where this was observed was 1991-2001. But before 1991 autism did not qualify as a reporting category. When you start reporting something new, there is going to be a dramatic increase. Increases will continue to be seen as more people become aware. States have all gradually increased their reporting at different levels and rates. For example, in the school year 2002-03, Oregon reported 4.3 children with autism per 1,000, but Colorado only reported 0.8 children per 1,000.
“Diagnostic Substitution” is another way in which autism rates are often mistakenly seen as elevated. The chart below shows rates of mental retardation decreasing at approximately the same rate that autism increases. Are there fewer children being born with what we used to call mental retardation? Probably not. Behaviors and learning disabilities that were present in order to make these diagnoses remain, we just assign them to a more specific diagnosis which is now under the ASD umbrella. This same pattern has been found in European countries as well.