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Archive for June 14th, 2010

The genetics of autism

Autism and autism spectrum disorders (ASDs) actually represent a rather large continuum of conditions that range from very severe neurodevelopmental delay and abnormalities to the relatively mild. In severe cases, the child is nonverbal and displays a fairly well-characterized set of behaviors, including repetitive behaviors such as “stimming” (for example, hand flapping, making sounds, head rolling, and body rocking.), restricted behavior and focus, ritualistic behavior, and compulsive behaviors. In more mild cases, less severe compulsion, restriction of behavior and focus, and ritualistic behaviors do not necessarily preclude functioning independently in society, but such children and adults may have significant difficulties with social interactions and communication. Because ASDs represent a wide spectrum of neurodevelopmental disorders whose symptoms typically first manifest themselves to parents between the ages of two and three, the idea that vaccines cause autism and ASDs has been startlingly difficult to dislodge and has fueled an anti-vaccine movement, both here in the U.S. and in other developed nations, particularly the U.K. and Australia. This movement has been stubbornly resistant to multiple scientific studies that have failed to find any link between vaccines in autism or the other favorite bogeyman of the anti-vaccine movement, the mercury-containing thimerosal preservative that used to be in many childhood vaccines in the U.S. until the end of 2001. Add to that the rising apparent prevalence of ASDs, and, confusing correlation with causation, the anti-vaccine movement concludes that vaccines must be the reason for the “autism epidemic.”

In reality, autism and ASDs appear to be increasing in prevalence due to diagnostic substition, better screening, and the broadening of the diagnostic criteria that occurred in 1994. Autism prevalence does not appear to be rising, at least not dramatically, at all, as the prevalence of ASDs, when assessed carefully, appears to be similar in adults as it is in children. If the true prevalence rate of autism and ASDs has increased, it has not increased by very much. In reality autism appears to have a major and probably predominant genetic component, and several scientific studies over the last few years have linked autism with various genetic abnormalities. Not surprisingly, given the varied presentation and severity of ASDs, these studies have not managed to identify single genes that produce autism or ASDs with a high degree of penetrance (probability of causing the phenotype if the gene is present). Indeed, one can argue that the state of current evidence is that ASDs are due to multiple genes, perhaps dozens or hundreds. Again, this is not surprising given the heterogeneity of ASD severity, presentation, and symptoms.

One of the more surprising studies supporting a genetic basis for autism appeared to much fanfare in Nature last week. The study by Pinto et al, looks at the functional impact of global rare copy number variation in autism spectrum disorders. Its results are rather surprising in that the large team of investigators (studies of this type take a lot of people to carry out) found that it may be relatively uncommon copy number variations in various genes that lead to the phenotype of autism or ASDs.
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Posted in: Neuroscience/Mental Health, Science and Medicine, Vaccines

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In which Dr. Gorski once again finds himself a target of the “pharma shill” gambit

EDITOR’S NOTICE: NOTE THE DISCLAIMER. Also note that there is a followup to this post entitled The price of opposing medical pseudoscience that is highly recommended after you read this post.

The “pharma shill gambit”: The quack’s favorite flavor of ad hominem argument

One of the very favorite and most commonly used tactics to attack criticism in the armamentarium of pseudoscientists, cranks, and quacks (not to mention politicians) is the ad hominem fallacy. In this fallacy, rather than addressing the actual evidence and science that demonstrate their favorite brand of woo to be nothing more than fairy dust, the idea is to preemptively attack and discredit the person. The ad hominem is not just insults or concluding that someone is ignorant because, well, they say ignorant things and make stupid arguments (in which case calling someone stupid or ignorant might just be drawing a valid, albeit impolitic, conclusion from observations of that person’s behavior), but rather arguing or insinuating that you shouldn’t accept someone’s arguments not because their arguments are weak but because they have this personal characteristic or that or belong to this group or that. Truly, the ad hominem is right up there with demanding public “debates” with skeptics as a favored defense strategy of cranks of all stripes.

Among the very favorite flavors of ad hominem attack used by quacks, cranks, and pseudoscientists is the fallacy of poisoning the well. This particular fallacy alludes to the medieval European myth that the Black Plague was caused by Jews poisoning town wells. Not surprisingly, this myth was used as a justification for pogroms and the persecution of the Jews. The idea is to poison how others view your opponent by preemptively attacking them. Well do I know this fallacy, having been at the receiving end of it many times! Basically, it involves invoking something bad or biased about a person’s situation or personality and then using a phrase something like, “Of course he (or she) would say that” to dismiss a person’s arguments, the implication being that the person receives such benefits from holding the position being attacked or has such a personality that he couldn’t argue otherwise regardless of the evidence. In my admittedly anecdotal experience, far and away the most common use of the ad hominem from quacks and pseudoscientists is what I once described as “the pharma shill gambit.” The idea behind this gambit when it comes to attacking those of us who promote science-based medicine is to tar one’s opponent as being a “shill” for big pharma or claiming that we have a conflict of interest so blatant that “of course we would say that.” In most cases, the bogey man is big pharma, in whose pockets we SBM bloggers are supposed to be safely (and profitably) ensconced, blogging away in our underwear for big bucks and, following the orders of our supposed paymasters, attacking anything that has even a whiff of being “alternative” or that “questions” the safety and/or efficacy of vaccines.

While I realize that there is such a thing as an “astroturf” campaign, in the vast majority of cases, the pharma shill gambit is nothing more than the variant of the ad hominem fallacy known as poisoning the well. I also realize that conflicts of interest (COIs) matter, particularly undisclosed COIs. Indeed, I wrote a rather lengthy post (I know, I know, do I write any other length of post?) about 8 months ago laying out my views regarding COIs in science-based medicine. The short version is that we all have COIs of some sort or another, be they financial, belief-based, or emotional, and more disclosure is usually better, to let the reader decide for himself. As far as COIs related to big pharma or finances, I think Mark Crislip put it quite well in his most recent Quackcast when he said that if a study is funded by big pharma, he decreases the strength of the evidence in his mind by a set amount. However, evidence is evidence, and, although it is reasonable to increase one’s level of skepticism if there is a major COI involving the authors, be it big pharma or otherwise, it is not reasonable to use that COI as the sole reason for rejecting its findings out of hand. That’s just an intellectually lazy excuse to dismiss the study, nothing more. Indeed, one prominent difference between a scientist and a pseudoscientist or quack is that in general scientists understand this and struggle to assign the correct degree of skepticism due to a COI when analyzing scientific studies, while quacks and pseudoscientists do not. It’s far easier for them just to put their fingers in their ears and scream “Conflict of interest! Conflict of interest!” and then use that to dismiss completely their opponent’s argument. It’s simple, neat, and it doesn’t require all that nasty thinking and weighing of evidence..
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Posted in: Medical Ethics, Neuroscience/Mental Health, Public Health, Vaccines

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