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Rain man? Or: Does rainfall cause autism?

Posted in Uncategorized by Skepdude on November 5, 2008

So it came as no surprise that a number of my readers have e-mailed me about a story about a rather odd little study about autism. Actually, it was a bit of a surprise when the first e-mail arrived, mainly because I hadn’t known that this study was in the pipeline or that it had been published, but soon I became aware that David Kirby was using it as “exoneration” and my usual sources started to weigh in. To some extent I was blindsided on this one, but I quick. So what is this story that’s buried my e-mail in box under, oh, around a dozen e-mails or so? (Hey, this isn’t Pharyngula, you know. I don’t get hundreds of e-mails about anything.)

There were stories in USA Today and MSNBC about a study that concluded that rain causes autism.

OK, that’s not really what the study claims to have found. In fact, the authors were pretty conservative about drawing inferences. However, it did claim to find a correlation between precipitation rates and autism prevalence on the Pacific Coast. The study, published in the November issue of the Archives of Pediatrics and Adolescent Medicine by investigators whose lead author is Dr. Michael Waldman of Cornell University and with collaborations with investigators at Purdue University, and the Children’s Hospital of Philadelphia (Paul Offit must be having kiniptions over this) and entitled Autism Prevalence and Precipitation Rates in California, Oregon, and Washington Counties. This study purports to provide evidence that autism prevalence is associated with precipitation. It seems to show just such a correlation, but there are a number of reasons to be very skeptical of the conclusions being drawn from this study, not the least of which are the uses to which mercury militia apologist puts it.


Rainman – Link Between Precipitation and Autism

Posted in Science Based Medicine by Skepdude on November 5, 2008

A new study published in the Archives of Pediatrics and Adolescent Medicine shows a positive correlation between counties in California, Oregon, and Washington with greater precipitation and a higher incidence of autism. While the results of this study are interesting, it needs to be put into proper context. Also of note, the authors had presented early results from this data previously.

Correlation is not Causation

This type of study is a correlational study, which means it asks whether or not there is a statistical correlation between two variables – in this case the rate of autism and the amount of precipitation.  This type of data is extremely useful to medical science, but it has known limitations, which can be summarized by the statement that correlation is not causation.

I often see this principle used to dismiss correlation data entirely, but that is not the correct approach. Correlation, rather, needs to be considered in the proper context. When A correlates with B there are various possible interpretations: the correlation is a statistical fluke (coincidence); A causes B, B causes A, or both A and B correlate with another variable C, and there can be a variety of causal relationships among the three (or more) variables which would cause A to track with B.

Therefore, finding a correlation is a way to generate several hypotheses which can then be tested by further observations or research. That, in my opinion, is the best way to view correlational data – as a beginning step to help generate hypothesis. But they should not be used to reach firm conclusions.

It should also be noted that further correlations can be used to test various causal theories, and if multiple correlations all triangulate to a single causal hypothesis that can lead to a fairly confident conclusion – even in the absence of other evidence. For example, smoking correlates with certain types of lung cancer. There are no prospective studies in humans to establish that smoking causes lung cancer, but we can be confident that it does because the correlation holds up no matter how you choose to look at it. If smoking causes cancer (as opposed to other causal hypotheses stemming from the correlation) then we predict that increased duration of smoking increases risk of lung cancer, that stopping smoking decreases risk, that smoking unfiltered is more risky than filtered, etc. Each of the predictions turns out to be true, supporting the smoking causes lung cancer hypothesis.


Vaccines: Separating fact from fiction

Posted in News by Skepdude on November 5, 2008

Yet underneath all the debate and impossibly good intentions (after all, everyone hopes to be doing the best for their child no matter how or whether they immunize), there are some solid facts about the benefits of shots that cannot be ignored. “We live thirty years longer now than we did a century ago, thanks to purified water — and vaccines,” says Paul Offit, M.D., chief of infectious diseases at the Children’s Hospital of Philadelphia in Pennsylvania.

But as soon as compliance wanes, the protection we have against many devastating, and sometimes fatal, diseases wanes right along with it. This year’s measles outbreak — the biggest in nearly a decade — may be the first warning shot, says Dr. Offit. Nearly all of the 131 people affected so far, many of them children, were purposely not vaccinated against the disease, according to a new report from the Centers for Disease Control and Prevention (CDC), in Atlanta, Georgia.

“We have to take this seriously,” says Anne Schuchat, M.D., director of the CDC National Center for Immunization and Respiratory Diseases. “I do not want to see the day where thousands of kids get this disease and die when we have the tools to prevent it.” Read about the vaccines your child is getting

So what’s a worried mom to do? Between the scary claims about shots themselves and the scary news about what can happen without them, you might feel like you need a Ph.D. in immunology, toxicology, and biostatistics to make sense of it all. To help, has highlighted four of the concerns heard regularly, and dug through the science to get the facts. The bottom line: No medical intervention is 100 percent risk-free, and no one but you can choose what’s right for your child. Our job is to help that decision come a little easier, so here goes:


Skepdude says-excellent article. I started reading it with a little bit of apprehension as I was affraid it was going to turn into one of those “listen to your mommy instinct” pieces. I am happy to announce it isn’t. Very nice little primer on vaccines and what worries most parents, and cool little debunking of the major lies about vaccines.

Stop Jenny McCarthy

Posted in Skepdude by Skepdude on October 17, 2008

We know what the false prophets think; now what?

Posted in ScienceBlogs BookClub by Skepdude on October 10, 2008

On the last day of the Science Blogs Book Club discussion about Dr. Paul A. Offit’s recently published Autism’s False Prophets: Bad Science, Risky Medicine, and the Search for a Cure, I’ll start by quoting the last paragraph of the book:

The science is largely complete. Ten epidemiological studies have shown MMR vaccine doesn’t cause autism; six have shown thimerosal doesn’t cause autism; three have shown thimerosal doesn’t cause subtle neurological problems; a growing body of evidence now points to the genes that are linked to autism; and despite the removal of thimerosal from vaccines in 2001, the number of children with autism continues to rise. Now it’s up to certain parent advocacy groups, through their public relations firms, lawyers, and celebrity spokespersons, to convince the public that all of these studies are wrong—and to convince them that the doctors who proffer their vast array of alternative medicines are the only ones who really care. (p. 247)Now that’s a laying down of the gauntlet. Those “certain parent advocacy groups” and their accompanying band of PR firms, lawyers, celebrity spokespersons, and the doctors who “proffer their vast array of alternative medicines” have their work cut out for them, if they mean to thoughtfully contest the claims of the numerous studies Dr. Offit cites.

But the problem is—-based on how the antivaccinationists have responded to the evidence so far—-they’re not going to respond to the science with science. Instead, expect full-page ads (like this one) in which there’s talk of not being “anti-vaccine” but “pro-vaccine-safety.” Expect a lot more moving of the goalposts as autism gets rebranded: So the link between thimerosal in vaccines and autism does not seem “so strong”—then it must be something else, like aluminum. In other words, don’t expect an actual discussion of the studies Dr. Offit cites but succinct slogans with just enough punch (“autism is treatable,” “green our vaccines”), criticisms of “conflicts of interest,” cries of the limitations of the data.


Hubris, Thy Name Is Jenny McCarthy

Posted in Neurologica by Skepdude on October 2, 2008

There are many words I could attach to the dangerous freakshow that is Jenny McCarthy – self-made advocate for the pseudoscientific notion that there is a link between vaccines and autism: deluded, self-righteous, irrational, the Mayor of Wooville, etc. But I am always interested in the process that gets people to their profound confusion. I believe at the core of Jenny McCarthy’s tragic crusade is an utter lack of humility.

Her lack of humility also seems consistent with someone who has never risen to a level of competence, let alone mastery, in any intellectual discipline. Those who have understand on some level the value of excellence and expertise, and the gulf that separates superficial public knowledge (or what has been called in the internet age, the University of Google knowledge) from a functional depth of understanding.

This brings to mind yet another word that could apply to McCarthy – sophomoric. She has garnered just enough knowledge to think she knows what she is talking about, but not enough to appreciate the depths of her own ignorance.


How they do the voodoo that they do so well – Part 2

Posted in Photon in the Darkness by Skepdude on September 22, 2008

End Games:

Eventually, even the most successful, charismatic “alternative” practitioner will have a patient who doesn’t improve enough to satisfy the parents. Not only are these parents a real drag on the “alternative” practitioner’s ego, there is the very real chance that they might start to talk about how “the Emperor has no clothes”. For those situations, there are a number of strategies that are typically used.

Did you follow my instructions to the letter?:

One of the oldest dodges in the “alternative” medicine “biz” is to prescribe a regimen of treatment that is too complicated for most patients to follow. If they get better (by chance), then it was due to the “treatment” – if they don’t get better….well, they didn’t follow all of the instructions exactly, did they?

Much the same is happening in “alternative” autism therapy. One of the first chelation regimens promoted for treating autism required that the parents give their children a dose every four hours around the clock for two weeks. This meant waking the child up in the middle of the night – every night – for two weeks and getting them to drink a foul-smelling liquid.

The parents were cautioned that missing a single dose – or being late by more than two hours – meant risking having more mercury deposited in the brain. This – needless to say – was absolute nonsense. But no parent who failed to see the promised results could honestly say that they had given every dose on time.