As the Autism Omnibus hearing is underway, the public debate about whether there is a link between mercury and thimerosal in vaccines and autism spectrum disorder is raging. Robert F. Kennedy Jr., who has been an outspoken proponent not only of the notion that mercury does cause autism but that there is a vast conspiracy to hide this truth from the public, yesterday published a ranting emotional and conspiracy mongering tirade in the Huffington Post. I am cautious about using hyperbole, but really there is no other way to characterize this shameful piece of dangerous nonsense.

The title of the piece, “Attack on Mothers” sets the theme and tone of the article. RFK Jr. writes:

“Mothers of autistics are routinely dismissed as irrational, hysterical, or as a newspaper editor told me last week, ‘desperate to find the reason for their children’s illnesses,’ and therefore, overwrought and disconnected.”

If you don’t have the science on your side I guess you have to exploit the emotions of a situation, which he does throughout the article. RFK Jr. paints a picture of intelligent, educated, “skeptical,” “dispassionate,” and “diligent,” mothers who are just following the evidence in a sincere hope to help their afflicted children. Arrayed against them are critics who are “lazy,” dismissive, and engaged in a campaign of fraud and deception. Reading this article I am reminded of other conspiracy fantasies that also paint in such stark good vs evil terms.

But RFK Jr. gets just about everything dead wrong.

First, skeptics of the mercury/autism hypothesis (that is to say most scientists) are not unfairly dismissing or being condescending to the parents of autistic children who believe that vaccines were the cause. If anything, they have been very patient and understanding. In most articles I have both written and read on the topic there is almost always the obligatory mention of sincere empathy with the parents and understanding of their plight. The parent’s experiences are not being dismissed – what is being dismissed is the reliance on anecdotal evidence. RFK Jr. relies heavily on such anecdotal evidence in his article as well.

The simple fact is, human memory is fallible, there are numerous observational biases that plague human perception, and anecdotal evidence has been proven countless times to be worse than worthless, it is in fact highly misleading. The parents of autistic children are not magically exempt from these factors because their goals are sincere and their burden great. What RFK Jr. misses is that it is possible for calm, educated, sincere parents to come to a completely wrong conclusion based upon their own experience. Only carefully controlled scientific observation can resolve the question.

RFK Jr. knows that the scientific evidence is the final arbiter of this controversy, which is why he then launches into a ludicrous summary of the scientific evidence to date. He says that there are “hundreds of research studies from dozens of countries showing the undeniable connection between mercury and Thimerosal and a wide range of neurological illnesses…” What he is referring to are the basic science studies that show that mercury is a neurotoxin – which is not in dispute. What is in dispute is whether or not the amount of ethyl mercury given in vaccines through thimerosal was neurotoxic and whether or not it in fact caused autism. Here the data is solidly negative.

But RFK Jr. is undeterred by the epidemiological evidence that overwhelmingly shows no connection between vaccines or thimerosal and autism. Like any good conspiracy theorist he has learned to dismiss inconvenient evidence with a conspiracy. He accuses the institutions and scientists who conducted four European epidemiological studies showing no connection of “borderline fraud” – basically making up these studies to protect the CDC, FDA and ultimately the vaccine producers from liability. He throws in the IOM (Institute of Medicine) for good measure. Basically anyone who disagrees with the conspiracy is part of the conspiracy.

RFK Jr. leaves out the fact that multiple other studies also show no connection – like this recent University of Columbia-Missouri study. He says that the conspirators are trying to block studies that could show a link – but the kinds of studies he wants have already been done, for example this epidemiological study. Pediatricians have reviewed the data and conclude there is no connection. But RFK Jr. is undeterred – they are all just part of the vast conspiracy. He can use any trivial connection to regulatory agencies or industry to dismiss all of it – what academic hasn’t gotten a grant, given a lecture, or consulted for some department that could produce some link. That doesn’t mean they were paid off to lie, to condemn millions of children to neurological disease. He also conveniently ignores the significant and real conflicts of interest for those few scientists, like the father and son Geier team, who are trumpeting a connection.

No where in RFK Jr.s article is there mention of the fact that in 2002 thimerosal was removed from routine childhood vaccines. That the proponents of the mercury hypothesis all predicted that this removal would be followed over the next few years by a sharp decline in the incidence of autism diagnoses. And that the incidence has not fallen, in fact it has continued to rise. This failed prediction was a death blow to the thimerosal causes autism hypothesis. It follows a basic scientific principle – if you think A causes B, then remove A and B should decline. Well B (autism) did not decline, so A (thimerosal) does not cause B.

Just to be clear, and head off any nitpicking, it is impossible to prove a negative – that something does not exist. All of the evidence gathered to date does not prove, and cannot in theory prove, that there is no correlation between thimerosal and autism. But evidence for a lack of correlation does set limits on how big a phenomenon can be. At this point we can say with confidence that there is no significant correlation between thimerosal and autism. Any possible remaining correlation would be tiny.

It is also worth noting, and a point not addressed by RFK Jr., that the alleged autism epidemic is likely not a real epidemic. The best epidemiological evidence we have to date suggests it is either mostly or completely an artifact of increased surveillance combined with a broadened diagnosis.

RFK Jr.’s article completely misrepresents the scientific evidence, relies heavily on anecdotal evidence and emotional appeal, makes outrageous accusations of a widespread evil conspiracy against just about everyone who disagrees with him, and tries to portray those who are simply defending good scientific thinking as being dismissive and condescending to the poor mothers of autistic children.

That is generally the quality of argument that exists on the mercury-causes-autism side of this debate. That is the intellectual integrity that is being brought to bear in the Autism Omnibus hearings. I can only hope that those defending legitimate science have the patience, endurance, and thickness of skin to endure the kind of smears that are being leveled against them. In this debate if science loses the health of the public will pay the ultimate costs.

Left brain/Right brain by Kevin Leitch
Denialism blog
Respectful Insolence by Orac