Tuesday, July 29, 2014
Robert F. Kennedy Jr. Is Badly Mistaken About Vaccines and Autism
A recent article by Keith Kloor in the Washington Post Magazine discussed the position taken by Robert F. Kennedy Jr., who has edited a new book claiming that the preservative thimerosal, used in some vaccines, is responsible for a large proportion of neurodevelopmental disorders, including autism (www.washingtonpost.com/lifestyle/magazine/robert-kennedy-jrs-belief-in-autism-vaccine-connection-and-its-political-peril/2014/07/16/f21c01ee-f70b-11e3). Kennedy is untrained in any of the scientific disciplines that would enable him to critique the evidence for such a claim. One of his co-authors, the physician Mark Hyman, is a purveyor of diets and alternative medicine as preventative of common disorders and as guides to “UltraWellness”.
According to the Kloor article, the book, Thimerosal-- Let the Science Speak, was published without some of the draft chapters, as even Kennedy’s co-authors felt they were too “combustible” (for which I read, “impossible to support with empirical evidence”). Nevertheless, the book makes strong claims about the dangers of the mercury-containing preservative, and attacks the Centers for Disease Control and other federal agencies for their unwillingness to remove thimerosal from all vaccines. Kennedy and his co-authors interpret the fact that thimerosal was removed from vaccines for childhood diseases years ago as an admission of evidence of toxicity, rather than as what it was: a policy decision taken to counteract the mistaken thinking of some parents, who wanted to avoid vaccination because they thought the procedure could cause autism. They reason (?) from this assumption that CDC and other agencies know they are in the wrong about thimerosal, but for unknown motives continue to maintain their mistaken position.
There are three basic ideas in all of the anti-vax, anti-thimerosal arguments, and all three are problematic. One idea is that because mercury in some forms and quantities is known to cause brain damage, all forms and quantities must have the same effect. Because people who ate fish contaminated by high levels of methylmercury effluents developed Minamata disease, with sensory disturbances, movement problems, and tremor caused by the mercury neurotoxicity, it is argued that occasional exposure to small quantities of other forms of mercury can have devastating effects. This is similar to arguing that because a person can drown in the ocean, salt-water nasal sprays are also dangerous. In fact, in spite of homeopaths’ claims to the contrary, minimal exposures can be harmless even though greater exposures to a toxic substance can be fatal.
The second idea depended on by Kennedy, Hyman, and others is that autism and other neurodevelopmental disorders are caused entirely by environmental factors. However, there is strong evidence that genetic factors are largely responsible for autism and most other such disorders. This can be difficult for concerned parents to accept, because they imagine that all genetic problems follow a simple dominant-recessive pattern as some eye colors do; when their child is diagnosed as autistic, the parents say “it can’t be genetic, because no one in our families ever had such a thing”. However, genetic problems may involve a number of genes and be evident only when all the required genes are present together. They may also emerge from mutations or other changes which occurred in previous generations but were not apparent until the present one. Of course, the importance of genetic factors does not mean that there must have been no environmental factor at work, but it might well mean that only persons with certain genetic make-ups are vulnerable to the effects of certain environmental events (as discussed by Beaudet in a Science article in 2012).
The third problematic idea is that there is an epidemic of autism. It is certainly true that many more children in the United States are diagnosed as autistic than was true in the past, but this is far from the same thing as an epidemic. What I am going to say about the frequency of autism diagnoses in the U.S. today has been said many times, but apparently it needs saying again: the number of cases of any disorder diagnosed depends on two different things-- the number there actually are, and the method of diagnosis. Before Leo Kanner proposed the diagnosis of autism, no children were diagnosed as autistic, but this is not likely to have been because there were no autistic children before the 1940s. Kanner did not “invent” autism or autistic individuals, but just called attention to an existing condition that had been confused with other speech problems and with mental retardation. Definitions, symptom lists, and ways of diagnosing autism have altered over the years, and the present approach to autism includes both serious disorders and many mild problems that received other labels in years gone by. Unless some dramatic changes occur, combining mild and serious disorders will obviously result in having a larger number of people assigned the combined diagnosis than would have been the case for each previous diagnosis separately. (Incidentally, this problem of categorizing and counting also applies to statistics about Sudden Infant Death Syndrome; while deaths attributed to SIDS have been reduced in number in recent years, there has been an increase in infant deaths whose causes are unidentified—the same number of deaths, but placed into different categories.) Categorization is one source of the “epidemic”; another is increased awareness (not to say frantic anxiety) among parents, and haste in seeking diagnosis of peculiarities which in the past were often dismissed as trivial individual differences. This haste can lead to early diagnoses of autism in children who are later identified as typical in development.
Kennedy and his co-authors are thus wrong about the existence of an epidemic of autism, about environmental causes of the disorder, and about the actual effects of exposure to small doses of the form of mercury in thimerosal. By continuing to press these mistaken points, they discourage parents from immunization in general (even though thimerosal has long been removed from vaccines for common childhood diseases), and from flu vaccines in particular, as these continue to contain the preservative. Kennedy’s celebrity status enables him to publish and push as scientifically based a position contrary to what scientific investigation actually shows, and to use this position to argue against all common sense that the Centers for Disease Control are deliberately working against public health needs.