1/05/2010

Just a Reminder of the Neuropathology of Autism and Accepted Scientific Findings

I've blogged several times before about the neurobiology of autism. All of the vaccines-stole-my-child-from-me group tend to go on and on, quoting Wakefield, Haley, Deth, or the Geiers' bad science. Conrick especially loves to do long, long dumps of citations that supposedly prove that the mercury did it.

I was pulling the latest articles from Pediatrics today and came across this paper from 2007 that I thought would be worth putting out there again as a reminder that while there may still be much to be learned about autism, there are things we do in fact reasonably know that the anti-vaccine side will not acknowledge.

All quotes are taken from Chris Plauché Johnson, Scott M. Myers and the Council on Children With Disabilities' (2007) "Identification and Evaluation of Children With Autism Spectrum Disorders."

In looking at the prenatal period, Johnson, Myers, et al. point out that:

"Because many of the developmental brain abnormalities known to be associated with ASDs occur during the first and second trimesters of pregnancy,141,142 environmental factors (eg, teratogens, such as thalidomide and valproic acid)73 are more likely to play a role in the fetus via maternal factors. It is possible that maternal illness (eg, rubella) during pregnancy plays a role.143,144 Recently, the possible association between fetal testosterone concentration and certain autistic behaviors such as abnormal social relationships and restricted interests at 4 years of age was investigated.145" p.1188

Here is an acknowledgment (longstanding) that environmental factors play a role in autism, but that it is during pregnancy.

So what do we really know?

"The most consistent neuropathologic findings suggest pathology that arises in utero. The association of increased risk of ASDs associated with prenatal exposure to teratogens, such as thalidomide and valproic acid, suggests that early insults during critical periods of brain development (as early as 20–24 days after conception in the case of thalidomide) may be sufficient to cause ASDs.171" p. 1189

There's still much to be learned, and there is the need to expand the research, to look at larger numbers of autistic brains, to verify these findings, but we have pretty good data suggesting that autism is set by birth. We have pretty decent research (despite the antivaxxers' hatred of said science) that vaccines have nothing do with it:

"Etiologic possibilities occurring after birth have been proposed—in particular, measles-mumps-rubella (MMR) vaccine153 and mercury-containing vaccines.154–156 In 2001, the Institute of Medicine157 reviewed epidemiologic population-based studies and concluded that there was no evidence of a causal association between the MMR vaccine and autism. Studies that examined the association between MMR vaccine and autism since the publication of that review have supported this conclusion. 27,95,103,158–161 Questions also have been raised about the effects of environmental mercury exposure (including mercury-containing vaccines) on brain development in ASDs and other developmental disabilities.154–156 Mercury, in its organic form, is a known neurotoxin with neurologic sequelae, including motor impairment and visual and intellectual deficits, depending on the age at exposure and the type of mercury. There is no evidence to date that children with neurodevelopmental disabilities, including autism, in the United States have increased mercury concentrations or environmental exposures. 162 Using large data sets from the United States, Sweden, and Denmark, to date, no consistent association has been found between thimerosal-containing vaccines and neurodevelopmental outcomes or prevalence of ASDs.27,95,162–164 Despite evidence to the contrary, a recent survey of parents of children with ASDs revealed that 54% believed that their child’s ASD was caused by immunizations; 53% thought it was caused by genetics 165 Although the previous discussion reveals the wide variety of conditions known to be associated with ASDs, currently, an etiologic investigation of the individual child with an ASD infrequently identifies a known cause in the absence of GDD/MR, dysmorphic features, a positive family history, and/or a focal neurologic examination." p 1189
What really ought to concern us is the survey numbers showing 54% of parents think their child's ASD is vaccine-related, and 53% think it was genetics. I assume there's some overlap, accounting for the over 100% accounting. I will see if I can pull the survey later.


Chris Plauché Johnson, Scott M. Myers and the Council on Children With Disabilities.
Identification and Evaluation of Children With Autism Spectrum Disorders. Pediatrics 2007 120: 1183-1215.

1 comment:

Roger Kulp said...

I have always taken a position slightly different from the anti-vaxers.While I am convinced mercury causes autism,I do believe it probably happens in the womb.

My mother had a lot of mercury fillings,something the antivaxers never seem to concerned about.

Nor do they seem all that concerned high fructose corn syrup,which has been around long enough to cause an epidemic in autism in the last twenty years.A baby whose mother drinks a lot of soda or eats a lot of foods with HFCS would get a hellluva lot more mercury than a vaccine or two.