EBD Blog

Over at Respectful Insolence Orac has a worth-a-read post about a law suit arising from the use of chelation as a therapy for Autism. Chelation, in this sense, is a process in which a compound that binds to metal atoms is injected into a person in hopes of extracting those metals from the person’s body. Some people who believe that mercury causes Autism advocate the use of chelation to remove mercury from individuals who have Autism. A couple of years ago I pointed to this case in an entry here at EBD Blog. There was an extended series of comments in which I described the evidence about chelation. Orac, who harbors an opinion of similar verticality as mine—which is to say very low—about chelating as therapy for Autism, comments on the suit brought against a doctor who treated a boy by chelation and during the therapy the boy died.

As happened last time I mentioned this story, someone is likely to come to the defense of chelation therapy for Autism. At that time (see the comments on my entry about a film on chelation) I was challenged to examine the evidence. I did and found it wanting. The favorable evidence is almost exclusively case reports—what are called “testimonials” in common language—rather than placebo-controlled studies that permit inferences about cause and effect. Anticipating this result, I quickly checked for newer info. I found an older paper by Bernard et al. (2002) that presents the rationale for the idea that mercury is a causal factor in Autism:

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder of unknown etiology in most cases. Studies of monozygotic twins report an average 60% concordance rate, indicating a role for both genetic and environmental factors in disease expression. A review of medical literature has shown that exposure to mercury, whether organic or inorganic, can give rise to the symptoms and traits defining or commonly found in ASD individuals. The discovery and increase in the reported prevalence of autism parallels the introduction and spread of thimerosal-containing vaccines. The onset of autistic symptoms generally follows the administration of thimerosal in vaccines, and symptom emergence is consistent with expression of mercury toxicity. Clinicians treating autistic patients have reported elevated mercury levels in urine post challenge with standard heavy metal chelators and improvement in function after mercury removal from chelation. These findings support a hypothesis that mercury in vaccines may be a factor in the pathogenesis of autism. Understanding of the underlying biological mechanisms of thimerosal toxicity in populations genetically susceptible to mercury’s effects might lead to effective medical treatments for autistic individuals.

Note that the argument is almost exclusively circumstantial. (Note also that they use weasal words, e.g., “mercury in vaccines may be a factor”.) They fail to do the heavy science needed to establish causal relationships.

By contrast, Doja and Roberts (2006) conducted a scientifically defensible analysis of existing research. Here’s the abstract for their paper.

Because of a temporal correlation between the first notable signs and symptoms of autism and the routine childhood vaccination schedule, many parents have become increasingly concerned regarding the possible etiologic role vaccines may play in the development of autism. In particular, some have suggested an association between the Measles-Mumps-Rubella vaccine and autism. Our literature review found very few studies supporting this theory, with the overwhelming majority showing no causal association between the Measles-Mumps-Rubella vaccine and autism. The vaccine preservative thimerosal has alternatively been hypothesized to have a possible causal role in autism. Again, no convincing evidence was found to support this claim, nor for the use of chelation therapy in autism. With decreasing uptake of immunizations in children and the inevitable occurrence of measles outbreaks, it is important that clinicians be aware of the literature concerning vaccinations and autism so that they may have informed discussions with parents and caregivers.

It’s inappropriate to dispense professional advice over the Internet, so I shan’t do so here. However, I can express my hope that people who consider controversial therapies strip away the irrational (often emotional) appeals of such therapies and look at the rock-solid evidence. Orac’s a pretty dang trustworthy source, so his blog’s a good place to start.

Bernard, S., Enayati, A., Roger, H., Binstock, T., & Redwood, L. (2002). The role of mercury in the pathogenesis of autism. Molecular Psychiatry, 7(2), S42-s43.

Doja, A., & Roberts, W. (2006). Immunizations and Autism: A Review of the Literature. Canadian Journal of Neurological Sciences, 33, 341-346.