I was just wondering if anyone has any idea why there is such an increase recently in the cases of Autism in the US. (Here is the Wiki article. Here is the chart by itself.)
As you can see, the growth is literally exponential. What would account for such a thing?
Actually, for starters, I have two theories. Mercury in fish, coupled with better diagnostic methods.
What do the rest of you think?
Mercury is pretty nasty, it wouldn’t surprise me if it was linked to just about any congenital health issues.
That said, I doubt it’s the cause of the increases in cases since I don’t think there’s a great deal more mercury in fish now than a generation ago. Studies should also be able to correct for that fairly easily as there are a shocking amount of people who just plain don’t eat fish.
Not necessarily better, but a more broad spectrum of what counts as autism is what I think would account for the lion’s share of the increase.
Also, I’m not sure how the numbers are counted. If that’s the number of diagnoses per year then the graph doesn’t necessarily show what you think it does. For example - a 40-year-old who is only now diagnosed would count towards 2012 stats, not 1972 where he should be, provided it’s congenital and he didn’t catch autism in the past year.
I think the question to examine first is that raised by the chart’s description:
“It is unknown how much, if any, growth came from changes in autism’s prevalence.”
There’s a nearly perfect correspondence between the raise in autism diagnosis and a drop in the diagnosis of Mental Retardation that pretty much explains it all by itself: http://photoninthedarkness.com/?p=158
It’s a chart of children between 6 and 17 cathegorised as having Autism: “Bar chart of the number (per 1,000 U.S. resident children aged 6–17) of children aged 6–17 who were served under the Individuals with Disabilities Education Act (IDEA) with a diagnosis of autism, from 1996 through 2007. Counts of children diagnosed with autism for each year were taken from Table 1-9 of IDEA Part B Child Count (2005) and from Table 1-11 of IDEA Part B Child Count (2007). These were divided by census estimates for U.S. resident population aged 6–17 taken from US census estimates for 1990–1999 resident population by age and the similar estimates for 2000–2007; for all years, the September population estimates were used.”
Per this article, it may be an autoimmune disorder, caused by a maternal immune system with too little to struggle against.
I suspect it’s almost entirely caused by changes in diagnosis, coupled in some cases with pushy parents demanding an “official” label for their special snowflake. (Viz the huge rise in allergies, ADHD, etc.)
Look at old censuses - they’re full of “imbeciles” and so on. Nobody gets labelled an imbecile these days, at least not officially 
Changes in diagnostic criteria are highly likely to be responsible for the perceived “exponential” increase, with other factors like increasing parental age playing a role.
Mercury is not likely to be a culprit, seeing as how the rising numbers of autism spectrum diagnoses are not correlated with increasing exposure to mercury. For instance, one alleged culprit, the mercury-based preservative thimerosal was removed from virtually all routine childhood vaccines over a decade ago and reported autism diagnoses have kept increasing.
the last i heard, having an older father increases the risk. people these days are probably starting families later.
That was my first thought too:
Though I think it is tricky to pinpoint an increase/decrease, what with changes of diagnostic methods/criteria.
The decrease in mental retardation rates is one enormous factor.
Other factors include maternal obesity:
Those are some pretty amazing charts, and quite convincing. As autism has gone up, retardation has gone down. The same people are just being re-classified.
I think there’s a lot of good evidence that what amounts for most of the supposed increase in autism are three factors. First, in the mid-90s, the definition of autism was expanded to include related disorders such as Asperger’s Syndrome and pervasive developmental disorder not otherwise specified. This created the category of Autism Spectrum Disorders (ASDs), which meant that more people who did not fit the classic definition of full-blown severe autism were now included in the diagnostic category. This is called diagnostic expansion. When you expand a diagnostic category, by definition you’ll see an increase. However, this doesn’t mean that the actual rates increased, it simply means that people with the disorders are now recognized as having them.
The second factor is that as rates of diagnosis of ASDs has increased, rates of diagnosis of mental retardation and other developmental disorders, and of learning disabilities, and of childhood schizophrenia, have gone down. This means that those children are now being more properly diagnosed with ASDs. This is called diagnostic expansion.
The third factor is earlier recognition and intervention, which is associated with a better outcome.
The other issues regarding increasing age of mother and father, obesity of mothers, etc., are still being investigated, but probably account for a smaller percentage of the increase that the first three factors.
As far as the genetic component goes, it has been postulated in Wired that the geeks are to blame - they can make big bucks in high tech thus attracting mates and are breeding more these days. The article states (about geeks):
“In another age, these men would have been monks, developing new ink for printing presses. Suddenly, they’re reproducing at a much higher rate.”
A more recent study in the Netherlands found similar increases in autism among children of IT workers.
Do you agree with this statement from the ‘A Photon In The Darkness’ site cited above?
I do not. I think knowing the cause for autism spectrum disorders is separate from the issue of “why are the rates increasing.” Knowing the cause might be beneficial in that we might be able to mitigate the disabilities that are associated with the most serious forms of autism.
However, the neurodiversity movement strongly objects to the idea that they need to be “cured,” so the issue I think is complicated. Searches for causes often are hand-in-hand with searches for cures, and some of the proposed “cures” for autism these days are barbaric and horrific (MMS/industrial bleach enemas, chelation therapy, chemical castration). In addition, would the reduction in autism result in a fundamental reduction in the diversity of contributors to society? I don’t know if Temple Grandin cares much about the cause of her autism, or thinks she needs to be cured.
I can refer you to How To Lie With Statistics, a book that should be in every Doper’s library, if not emblazoned in their brain.
The author, Darrell Huff, devotes a section to “Did somebody change the subject?” which describes much of what is happening here. Change the definition and you will change the statistics.
It’s also important to note that there is no definitive test for autism, just a nebulous collection of symptoms, many of which describe active children. How much is hyper-active, how much is normal? Depends on what you want to prove, and who observes it.
While you are absolutely correct that there is no definitive test for autism, I’m not sure I agree with your statement that many of the symptoms of autism describe active children, at least not the DSM-IV diagnostic criteria.
Some of the symptoms:
From here. Now tell me these aren’t subjective?
“Less likely,” “smile less,” “respond less,” “less eye contact”? Highly subjective criteria. If you are looking for “symptoms,” you will find them.
I’m encouraged to read that. For parents that are fighting for resources for their ASD kids either from insurance companies, school districts, etc. seeing phrasing like “so-called epidemic” can be infurating.
While it’s possible that increases in autism rates don’t meet the technical definition of ‘epidemic’ if reclassificaiton of diagnosis is the cause, the CDC has not determined that to be the case. I don’t believe it to be true myself anecdotally.
[QUOTE=CDC]
Q: Is there an ASD epidemic?
A: More people than ever before are being diagnosed with an ASD. It is unclear exactly how much of this increase is due to a broader definition of ASDs and better efforts in diagnosis. However, a true increase in the number of people with an ASD cannot be ruled out. We believe the increase in the diagnosis of ASDs is likely due to a combination of these factors.
[/QUOTE]
The CDC does define it as an urgent public health concern. The less money spent on autism research the more you’ll see parents grasping at the therapy and treatments outside of science and critical review.
The condition known as autism is real, but the epidemic may not be.
