The Hygiene Hypothesis and Autism

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For those who don't want to read the articles, it is basically that:

1. Autism is an inflammatory disease

2. Studies show that inflammation in other diseases may be caused by a microbial deprivation, meaning our world is too clean and hygienic, and we aren't exposed to enough parasites and microbes when we're young, which leaves us with an immune system that overreacts to stuff, thus causing inflammation behind autism, allergies, and a number of other things. One version says that our immune system is not properly "trained" as a result of the deprivation when young, so our cytokines overreact like an autoimmune disorder (see this book for a good description: http://www.amazon.com/Infectious-Behavi ... B005S8P3BA). The version quoted in the New York Times says that actual parasite infection limited inflammation in our ancestors.

3. This is supported by the lower prevalence of autism in rural areas and third world countries.

From The New York Times:

http://www.nytimes.com/2012/08/26/opini ... d=all&_r=0

What basis is used to assume that Autism is an inflammatory disease in the first place?

Funny ... I don't feel inflamed ... or diseased, either ...

I was born in a country town in the 60's.
Cleanliness with two boys is a high improbability; aka, not likely.

I can see a correlation with regard to some "observed traits". But that is a long way from understanding why those traits exist from the point of view of the Autistic person.

I can't see this theory getting anywhere... lol

That correlates inflammation in the brain with autism, but not as a causative factor.

Correlation is not causation.

More direct explanatory discussions linked below. Besides, there have been a number of rodent studies where induced inflammation caused autistic behaviors: https://imfar.confex.com/imfar/2013/web ... 12373.html

One where the hypothesis was even tested with a successful treatment of autistic behaviors in rodents: http://www.sciencedaily.com/releases/20 ... 182019.htm

More explorations of the inflammation-autism link by peer-reviewed scientific publications:

Prenatal inflammation linked to autism risk

http://www.nih.gov/news/health/jan2013/niehs-24.htm

Neuro-inflammation, blood-brain barrier, seizures and autism
http://www.jneuroinflammation.com/content/8/1/168

And a proposed mechanism:
http://www.jneuroinflammation.com/content/10/1/46:

We'll see how the human trials pan out.

Don't really have the time to look into your links just now, and I'm not sure that I'm knowledgeable enough about the subject to assess the validity of the claims. But I think that some of your arguments supporting the hypothesis are flawed, specifically those relating to the lower incidence of autism in developing countries/rural areas, and its prevalence in middle class white families. How do we know that it isn't that middle class white people with autism are more likely to be diagnosed than people with autism from a developing country or rural area?

Edit: And the thing about the "idiot savants" does not seem to be very applicable here. First off, we are undeniably better off with the possible over-cleanliness now than we were back in the nineteenth century when people died of cholera contracted from contaminated wells, etc. Second, and more to the the point, 19th century scientists probably weren't entirely unbiased towards the social class from which many of them came themselves. "Idiot savants" in the upper classes would have been wealthy enough to support themselves without having to function at the same level as other people, right? But, potential "idiot savants" from the lower classes who weren't capable of supporting themselves without large inheritances, would very likely have ended up desperately poor if not out on the streets, and they probably weren't terribly well educated, so even if an illiterate individual were able to nurture some sort of savant-like talent, I imagine that it probably wouldn't be seen as intellectual enough by the scientists of the day to warrant being seen as a savant-like talent, and thus the "idiot savants" of the lower classes were probably simply deemed "idiots" or "that beggar on the side of the road".

I also think that you're creating a false dichotomy here between people who think that this hypothesis is valid, and people who believe absurd things such as autism being the next step in human evolution.

I'd like to point out that Dr. Hans Asperger wrote in his original paper:

"We are convinced, then, that autistic people have their place in the organism of the social community. They fulfil their role well, perhaps better than anyone else could, and we are talking of people who as children had the greatest difficulties and caused untold worries to their care-givers."

Autism Spectrum Disorders may well actually not be a disease in its entirety, but a natural variation such that there are benefits it can produce to humanity as a whole.

That being said, I would like to point out that there are a few sources which have pointed out that there has been an apparent rise in the number of people with ASDs world wide in the past decade or so, such as

Baron-Cohen S, Klin A (2006). "What's so special about Asperger Syndrome?" (PDF). Brain Cogn 61 (1): 1–4. doi:10.1016/j.bandc.2006.02.002. PMID 16563588

There may be several reasons for this, such as that the benefits of Autism Spectrum Disorders are now more necessary than ever, and Asperger's/Autism really is a step up in human evolution. Alternatively, if the inflammation hypothesis is true, then this newer climate of wiping out too many bacteria, is still allowing for ASDs to increase in number, and hence natural selection is still taking effect.

Natural Selection, as Darwin originally put it, is simply that those traits that allow for the best adaption in an area, will out-compete and survive, traits that don't fare as well IN THAT AREA!

So I would argue that either way, evolution and natural selection are favouring Autism Spectrum Disorders, if only to give humanity a wakeup call with regard to some of the problems it is facing, be it through alerting us to the issues regarding killing off too many bacteria, or by allowing the promulgation of certain heightened analytical capabilities that come with some ASDs, to hopefully provide workable solutions to other problems that humanity is facing.

To sum up, I'm saying that ASDs may or may not be the next step in human evolution, but evolution is certainly favoring ASDs at this time, regardless of the reason.

I wouldn't rule out a connection with inflammation in some way. However, why isn't the entire population in the developed world autistic in that case? Are you/they saying that only people with certain genetics will succumb to the inflammation and become autistic?

The thing is, that as autism seems to have a variety of components and a variety of genes involved, I don't think it can be so simple as to say that all autism (or perhaps even a certain type of autism) is caused by inflammation.

Maybe it plays a part when a whole host of other things (including genetics) create the perfect storm.