Saturday, December 22, 2007

Making stuff up: a novel form of evidence

Of all the whoppers told by the autism bio-med/conspiracy buffs, none may be easier to refute than that chestnut which tells us that the symptoms of mercury poisoning are "exactly the same" as autism. This line is repeated over and over with great certainty, as if it is as obvious as the setting sun.

The talking point was supersized in 2000 when Medical Hypothesis, a fringe journal for junk scientists, published Autism: A Novel Form of Mercury Poisoning. When somebody writes Dandruff: A Novel form of Skin Cancer, it will also find a home in Medical Hypothesis. The 2000 paper was widely quoted by parents who needed something to blame. Mercury seemed so obvious - it is known to attack the nervous system, and it's present in thimerosal, and the symptoms of autism present right around the time that infants are immunized. So there ya go - case closed!

Yet a simple comparison of the clinical symptoms of mercury poisoning and the diagnostic criteria for autism shows they are quite distinct.

As Pediatrics tells us, the characteristic motor findings of mercury poisoning are ataxia (gross incoordination of muscle movements) and dysarthria (motor speech disorder).
The outcome of fetal methyl mercury poisoning in severe form also included spasticity. In contrast, in autism, the only common motor manifestations are repetitive behaviors (stereotypies) such as flapping, circling, or rocking. Persons with Asperger syndrome may be clumsy, and hypotonia has been noted in some infants with autism; the frequency of clumsiness and hypotonia in autism spectrum disorders is not established. No other motor findings are common in autism, and indeed the presence of ataxia or dysarthria in a child whose behavior has autistic features should lead to careful medical evaluation for an alternative or additional diagnosis.

Fetal exposure to mercury frequentlyt leads to microcephaly - a small head. But prenatal exposure to lead, alcohol, PCBs and other neurotoxins, for example, also tend to decrease head size. "In contrast", notes Pediatrics, "in autism increasing evidence indicates that head size and, as measured by volumetric magnetic resonance imaging, brain size tends to be larger than population norms."

I guess that's where the "novel" part comes in.


Cross posted at AutismNewsBeat.com

5 comments:

EFFIIIMD said...

I am gonna do the science that you probably don't want to see. You may even be right and actually all of my pediatrics colleagues will be joyous of that; as will I. I don't have to be the one to show the rate of autoimmunity/autism and iatrogenesis stratified to number of vaccines with and with out thimerosal, but ending this debate will be good for the nation. A definitive answer from a prospective study will be cathartic, don't you agree?

ANB said...

Maybe you could find a population outside of the US that has a less aggressive schedule, and compare its rate of autism to our own. Heck, maybe somebody's already done that for you. I guess that would all come in a lit review, though.

As far as not wanting to see honest science preformed, well, to quote the Gipper - "There you go again!" Assuming facts, that is. ;-)

EFFIIIMD said...

A population outside the US would be a different genetic and envrionmental mix, so it weakens the science at how vaccines impact autism rates in this country. ANB unless you clearly state for all here that we should pursue my scientific approach to this, one must assume you are afraid to admit that you really aren't interested in the most discriminating science on this issue. I can't wait for this to get done now. You are pushing my impetus to spread the word and do the science.

So that I do not assume anything about you on this, will you make a statement in writing on the blog as a hidden identity that this is the science that we all need to push for? I will have real respect for you if you do the same on your personal website. If you can't be willing to allow the most scrutinizing approach to this problem then I will continue to assume you are in no way interested in protecting the health of this nation's children. There I go again, making assumptions just like I assume my car will start this AM on my way to the hospital where I will be saving more lives by artful perception.

Anonymous said...

The very last sentence of that opinion piece: "On the basis of current evidence, we consider it improbable that thimerosal and autism are linked."

Fogarty said...

We need to prove it now don't we? We cannot continue to ASSUME its safety record in industry influenced epidemiology and then does this crap out to the rest of the world's children. Simple idea here-build a better mouse trap than one built in the 1930's.