Sunday, March 30, 2014

Autism Rising : The Emperor's New Clothes

It's that time of the year again - winter is finally starting to fade, spring is in the air, and Autism Awareness month is right around the corner.  Which means that it is time to play one of my favorite games - rationalize about the latest massive increase in the rate of autism.

In case you haven't heard, the CDC just this week released the latest in its series of reports on autism prevalence.  This new report which looked at children who were eight in 2010 found that overall 1 in 68 children had a form of autism - 1 in 42 boys and 1 in 189 girls.  

Since a picture is worth a thousand words, here is what the CDC's autism prevalence figures have looked like over the past 10 years.

As you can see the autism prevalence figures from just this one source have more than doubled in just ten years.  I have to wonder how much higher the rate is going to have to go before public health officials and the medical community start taking the problem seriously.  What does the number have to be before we stop trying to explain away the increase and start acknowledging that the increase just might be because more people are developing autism?

The CDC's explanation this year is a mixed bag of more children with typical intelligence being recognized, "better awareness", and, somewhat strangely, saying that even more awareness is needed in certain areas.  Entirely missing from the explanation or interpretation is anything that suggests there might be a very real problem.

How can it be that after ten years of study the CDC can't figure out if the increase is real?  How can they say in their 2000 report when the new, unexpectedly high rate was 6.7 per 1,000 -
Studies of ASD prevalence in the United States during the 1990s have identified rates of 2.0 - 7.0 per 1,000 children, a greater-than-tenfold increase from rates of 0.1 - 0.4 per 1,000 children identified during the 1980s. [...] However, because the number of persons identified for services is dependent on multiple factors (e.g., changing eligibility criteria, increased awareness, and changes in service availability), aggregate data might underestimate prevalence and should be used with caution in examining population-based trends.
And now, ten years later, when the rate is 14.7 per 1,000, when there are more than 2 children with a diagnosis of autism for every one back then, they say -
The global prevalence of autism has increased twentyfold to thirtyfold since the earliest epidemiologic studies were conducted in the late 1960s and early 1970s. At that time, prevalence estimates from European studies were one in 2,500 children in the population, and by the 2000s prevalence estimates from large surveys were 1%–2% of all children. Although the underlying reasons for the apparent prevalence changes are difficult to study empirically, select studies suggest that much of the recent prevalence increase is likely attributable to extrinsic factors such as improved awareness and recognition and changes in diagnostic practice or service availability.
How can the expected rate of autism go from 1 per 1,000 to 6.7 per 1,000 to 14.7 per 1,000 and the explanation stay the same?

To preempt any snarky comments, yes, there are some external social factors that can explain away some of the increase without their being an actual increase in the number of people with autism.  But to suggest that there were 14 people with autism in the past for every 1 that was identified but no one noticed due to social issues is just absurd.  It is very hard to miss a large number of children who have functional language issues, don't socialize well, have restricted interests, repetitive behaviors, sensory issues, and the tendency to meltdown on a regular basis.

The other part of the CDC's explanation, the idea that increase is bring driven by children with more typical intelligence, is complex one that would require its own post. But, suffice it to say, like last year's "later diagnosis" theory it doesn't hold up under close scrutiny.  The increasing IQ numbers could easily be attributable to the increasing availability and use of early intervention services such as speech therapy and ABA.  If you start increasing a child's receptive and expressive communication ability and teach them how to better self-regulate then, everything else being equal, they will be score better on an IQ test.

Besides which, since these numbers are in line with last year's NSCH increase but are based on one static age, how can you reconcile the current findings with last years?  Especially since the median age of diagnosis did not change in the current CDC report from the one before?  Oh wait, you try to do it like so -
Comparison of findings from the ADDM Network 2010 surveillance year with results from the CDC 2011–2012 National Survey of Children's Health (NSCH) on parent-reported ASD prevalence (5) revealed some similarities. Collectively, these two studies used three complementary data sources: health (ADDM), education (ADDM), and parent-report (NSCH). The report based on NSCH data estimated ASD prevalence of 2.0% among children aged 6–17 years in 2011–2012. Like the ADDM Network, NSCH also found a large increase in ASD prevalence compared with its previous estimate, which was based on 2007 data. The NSCH attributed this increase to children who received diagnoses at an older age, with a greater proportion judged as having mild (less severe) ASD according to parent report. Although not synonymous with ASD without co-occurring intellectual impairment, the increased number of children with milder ASD diagnosed at an older age in the NSCH study parallels the increasing percentage of children with normal intellectual ability and ASD identified in the ADDM Network.
In other words, the NSCH report attributed the increase to increased number of milder, more intelligent children being diagnosed later in life (i.e. after age 8) and the current CDC report says that is comparable to milder, more intelligent children being diagnosed earlier in life (i.e before the age of 8)?  Even though the NSCH data is more recent than the CDC data?

To leave you on a happy note, the most recent data from the CDC is already quite stale because it is talking about children who were born in 2002.  It doesn't tell us what the rate of autism is in children who are being born today.  Given that the rate has gone up considerably every time we look at a later birth year I think it is safe to assume that the rate for children born today is much higher than 1 in 68.

If you want to get an idea of what the numbers might look like for children born after 2002 you can look at the NSCH numbers.  But  the NSCH data contains a lot of extra noise that makes it hard to compare to the CDC numbers.  However, if you take the data from the last three NSCH data sets, pull out the data on the children who were eight at the time, and chart it with the CDC numbers by birth years you get a somewhat clearer picture -

The numbers aren't exactly comparable because of differences in how they are derived.  The NSCH data is based on parental report and might be overstating the rate.  But the NSCH data also covers a much larger part of the country than the CDC numbers do so might be more representative of the country as a whole.

In any event, I think it is interesting that the two disparate data sets are showing the same trend.  If you measure the same thing in two different ways and come up with a similar answer then that tells you your answer is probably correct.

If the trend in the two data sets has continued to current day then the autism number for children born today will be about 1 in 25.  Maybe in twelve years when the CDC releases data for children born this year we will be treated to explanations about how our awareness is so much better than it was today.  Because, like ten years ago today, we would finally be seeing the half of the autism population that we can't see today.


  1. The ADDM from survey to survey is never taken in exactly the same parts of the country. They use different areas each two years. They use different counties within the same area. At least 20% of the people don't have a diagnosis of autism, but have evidence from school records only suggesting an ASD, even more of the purported cases of autism were just extrapolations from various records or the reports from school districts which may not have a diagnosis. The NSCH data was just a survey with a voluntary response and people who believe their kids are autistic might be more inclined to respond and since it was a phone survey there is no proof of legitimate diagnosis. Actually, instead of higher, the prevalence may go lower in the coming years now that the DSM 5 is used and the prevalence for the 2010 cohort was ascertained with DSM 4 which is now an obsolete instrument. I don't know why it would increase so much in just a two year period. It seems unlikely it was from any intrinsic factors.

    1. Hi Jonathan,

      The DSM 5 wasn't released until 2013 - after the data for 2010 was collected. The next brith year (2004) the CDC is going to be report on will all have been diagnosed before the DSM 5 too. So I wouldn't expect the DSM 5 to come into play for the CDC data for least another 2 or 3 cycles.

      Besides, the DSM 5 autism criteria contain an escape hatch that says that any DSM IV autism diagnosis is still valid under the DSM 5 which makes the whole point rather moot. If you have DSM IV autism then you meet the criteria for DSM 5, at least if you were diagnosed in 2013 or earlier.

      In general, I don't think we will see any real DSM 5 numbers for another five or ten years. It is only starting to come into use now and will take a few more years before it is the standard everywhere.

  2. It's a game. Fear Factor. So many professionals need to send their kids to college, why not give a label of mental illness to their kids and scare the hell out of their parents. My son is 20 now. If I had known how far he would come, I would not have worried. At all. He just needs time. I"m not saying he's not developmentally delayed. I am saying he will make it on his own one day, I know.

    1. I LOVE that you're saying this. And, I know some people's kids get to 20, and they're still having horrible problems, BUT, silver lining. :)

  3. How many kids are being dx'd because of ID?? LD's?? Shyness?? Apraxia etc etc etc. Lots. Why?? Because they can get in school services. Period. Truly, it's that simple... services. School's and health insurance runs on dx's without them you get NADA. Do I blame them... not at all. But it should not happen in a perfect world.

    Read the books out now written by those that wrote the IV... anyone, can be dx'd by anything under the IV per my Dr and those authors. They admit, autism, ADD and childhood bipolar are false epidemics and hopefully corrected under the V but... there will be others.

    Here's to hoping the V returns the numbers to where they should be.

  4. None of these questions are going to be answered until the medical profession actually discovers what biological/neurological mechanisms are affected in autism and how they are affected. There is no objective medical test to diagnose it - it is still a behavioural diagnosis. Until this question is answered, we will get nowhere. In many ways, we are still in the 1950s when autism was blamed on "refrigerator mothers".

  5. Well there's been a spike in diagnses, and some ppl say it's overdiagnosed - but my psych teacher of the last semester told us that she usually replies then "if it's overdiagnosed, so why it's so often undertreated?"

    and I think it's wonderful point.