A little critical thinking, please.

I’m a little pressed for time today, but not wanting to neglect this space, I thought I’d pass on an excellent article discussing the merits of the persistent myth linking autism with thimerosal-containing vaccines, and the MMR (Measles-Mumps-Rubella) vaccine in particular.

This is of particular relevance this week because the scholarly journal People Magazine (ahem…) has put this issue on the front cover of its July 2, 2007 edition, as the result of a recent lawsuit surrounding the issue.

Suffice to say, there is no evidence suggesting that thimerosal-containing vaccines cause autism. As the Skeptic.com article argues, we cant ethically do an RCT on this subject, so experimental evidence is difficult to obtain. However, the vast majority of well-conducted observational studies do not support a link (see here and here for two review articles on the subject or here if you’d like to review the primary literature). The most reasonable hypothesis is that the diagnosis of autism is now much broader than it once was, leading to a reclassification of children who would not have previously been called “autistic”.

This is the same reason why 5-year survival rates from cancer are poorly correlated with ultimate survival; early detection may simply increase the duration of time between a diagnosis of cancer and mortality from the disease. That is, if a tumour is detected earlier than it would have been say 10 years ago, all you’ve done is changed the time of diagnosis; you haven’t improved ultimate mortality at all. Granted, for many cancers, early detection improves the success of therapy, which does decrease mortality. But the lack of correlation between 5-year survival and mortality indicates that we must be very careful in our interpretation of data such as these.

Without any further digressions into my own area of expertise/interest, I will simply state that the skeptic.com article is highly, highly recommended.

These claims, which nearly all of the high-quality evidence suggest are entirely spurious, are not innocuous: they divert time and energy (not to mention badly needed money) away from real science. Indeed, the article closes with a concept that all conspiracy theorists and amateur “scientists” should heed:

Clarifying misguided claims of causative factors can help redirect necessary resources to more promising treatments, and perhaps reveal a better understanding of the real factors that cause autism.

I remain,



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