Autism Street

By now, many of you have heard about a new study from California’s UC Davis MIND Institute that shows a continuing increase in autism caseload. There has already been a lot of speculation about what this study may mean in terms of potentital autism etiologies, but I’ve also seen some good critical thinking about what this study is really capable of telling us.

Is the Rise In Autism Rates Real?

The MIND Institute’s Second Attempt: More of the Same Type of Reasoning

Some Facts of Interest About the Numbers From the MIND Institute Study

Why is David Kirby grasping at straws? - Comment

Questioning the new MIND study on prevalence of autism

In fact, what the study’s authors apparently conclude in the paper itself seems appropriately skeptical:

Autism incidence in California shows no sign yet of plateauing. Younger ages at diagnosis, differential migration, changesin diagnostic criteria, and inclusion of milder cases do not fully explain the observed increases. Other artifacts have yet to be quantified, and as a result, the extent to which the continued rise represents a true increase in the occurrence of autism remains unclear.

Emphasis mine.

I haven’t read the paper yet, but as I understand it, it’s also noted that the study does not account for increased awareness -  which is something that would  be very difficult to quantify, but also something that has a potentially huge confounding impact on determining whether or not any increase in autism caseload represents a real increase in autism.

It’s clear to most, that autism caseload in California is not descriptive epdiemiology in a strict sense, but rather a measure of the numbers of autistic people receiving services from the CDDS, and that interpretations based on such measurements are also subject to some serious limitations. However, if for the moment (and with acknowledgement of these limitations), we accept the information as potentially useful, can we learn anything else about this California data?

It would seem that many an “autism advocate” has warned us of an impending “crisis” that looms for California’s healthcare systems and schools. If autism caseload is increasing, and it represents a real increase in autism itself, then a next logical conclusion is that, ceteris paribus, similar increases will also be seen in the total numbers of children in special education in California’s schools, right?

Wrong - well, maybe wrong.

To look a little more closely at this, let’s look at part of a post from blogger Lisa Jo Rudy over at About.com:Autism

Schools are overwhelmed with children diagnosed on the autism spectrum. In part, that’s because a new category CALLED “autism” was created by the Department of Education during the 1990’s.

Rudy is correct about autism being a relatively new category, but we can dig deeper in regard to the situation in California - data from the department of education about category use for the past ten years in California, is available online. Are schools in California being “overwhelmed” with children diagnosed on the autism spectrum?

Here’s what the IDEA data for California kids in elementary, middle, and high schools shows:

 
Remember, like the CDDS client data, the IDEA is not descriptive epidemiology.

The USDE data are not reliable for tracking the prevalence of autism, and they in fact never were meant to fill this need.

Source

But what we can learn from this, is that there has been an increase in the number of kids receiving special education services who wear an “autism” category label. So there you have it. There has been an increase, and that increase has arrived at the schools, “overwhelming” them.

Of course the, “not so fast” is next.

The Invisible Epidemic

The next graph shows a bigger picture in California. It’s the number of students (age 6-17) receiving special education services, as a percentage of the population (age 6-17) for all disability categories.

The percentage has been flat, at about 9.15%, for 10 years! How is this possible? If there have been increases in the autism category, all things being equal, we should have seen this number rise, shouldn’t we? And therein lies one potential answer - all things are probably not equal. It’s true that within the IDEA data for California, the increase in the use of the “Autism” category label is not offset by decreases in the use of the category label “Mental Retardation”. The increase is also not offset by a corresponding decrease in use of the label “Speech or Language Impairment”.

Speech or Language Impairment

A communication disorder such as stuttering, impaired articulation, a language impairment, or a voice impairment that adversely affects a child’s educational performance.

Source

So what else is there? Something big in California?

Specific Learning Disability

A disorder in one or more of the basic psychological processes involved in understanding or in using language, spoken or written, that may manifest itself in an imperfect ability to listen, think, speak, read, write, spell, or to do mathematical calculations, including conditions such as perceptual disabilities, brain injury, minimal brain dysfunction, dyslexia, and developmental aphasia. The term does not include learning problems that are primarily the result of visual, hearing, or motor disabilities, of mental retardation, of emotional disturbance, or of environmental, cultural, or economic disadvantage.

Source

I can see how, in days of lower awareness and recognition of autism among parents and educators, an autistic child could easily be placed in this category (as a kind of catch-all), based on the first portion alone - “A disorder in one or more of the basic psychological processes involved in understanding or in using language, spoken or written…”. It could even be the case, that alongside less awareness and recognition, there was also some degree of unwillingness to use a category label like “Autism” on the part of both parents and educators.

Back to the UC Davis study for a moment - Principal investigator, Irva Hertz-Picciotto, has been quoted at WebMD as saying:

 ”When you put it all together, this doesn’t come close to explaining the increases in the last 10 years,” Hertz-Picciotto tells WebMD. “The more you whittle away at this increase, the more you have to say that what is left over is real. … Given that autism cases keep going up, and can’t be fully explained by artifacts, environmental factors deserve serious consideration.”

Source

Remember, this quote is from a media story, and it’s only fair to point out (once again) that the conclusion in the actual paper was apparently far less speculative:

Autism incidence in California shows no sign yet of plateauing. Younger ages at diagnosis, differential migration, changes in diagnostic criteria, and inclusion of milder cases do not fully explain the observed increases. Other artifacts have yet to be quantified, and as a result, the extent to which the continued rise represents a true increase in the occurrence of autism remains unclear.

Again, emphasis mine.

One thing seems clear though, quantifying those “other artifacts” may be a good idea, otherwise we need to start looking at why a “real” increase in number of children aren’t showing up in the California schools.