Saturday, October 08, 2005

Reviewing the theory of a thimerosal based etiology for the autism spectrum: A partial review of Generation Rescue's 25 myths

I was reluctant to begin this post. The thimerosal debate is not very friendly. Also, bad things can happen when we leave our area of knowledge and trod into someone else’s. I am not a medical student or toxicologist. I have only a very novice understanding of chemistry. All the same I can and do have a knowledge base in epidemiology and in research design. The thimerosal argument can not be effectively made in the absence of the previous two disciplines. I will focus my critique on these points.

I thought the best way to focus on this will be to look at certain myths in Generation Rescue’s “25 Mercury Myths” (Generation Rescue, 2005).

Myth 1

“There is no evidence to suggest that autism is genetic. No autism gene has ever been found and the search will be endless - how can you have a gene for a mythical condition? Autism is mercury poisoning. What is true is that certain children may have an impaired ability genetically to detoxify heavy metals from their systems. These children are more likely to be affected by mercury exposure. However, all children, and adults, if given too much mercury will manifest symptoms of mercury toxicity, which we call "autistic" symptoms. All children born from 1991 forward who received all recommended vaccines were injected with levels of mercury that dramatically exceeded safety levels set by the Environmental Protection Agency for adults. Mercury has become ubiquitous in our environment: in fish and other foods, water, and air. Exceedingly high doses of mercury exposure can result in death - it is that neuro-toxic and damaging to the human body. Two drops of dimethylmercury spilled onto the gloved hand of a Dartmouth chemistry professor, a leader in a study investigating mercury's causal role in cancer, resulting in the progressive loss of her balance, speech, vision, and hearing, and ultimately lead to her coma and death within a year of the exposure.”

No gene has been found which causes autism, that is correct. If autism is mythical why does there seem to be certain cognitive traits (strengths and weaknesses) that have been identified in the research. Is this a departure from what is known about other heavy metal toxicity? Why do older persons who have been exposed to mercury not receive the diagnostic of autism then, it seems there are important dissimilarities.

“It is impossible to have a "genetic epidemic." Since 1991, there is a very real and dramatic rise in the incidence of autism and other neurodevelopmental disorders. In the 1970s, the incidence of autism was 1 in 10,000 children. In 1986, the rate was 1 in 2,500. Today the rate is 1 in 150. It has been estimated that one in six children have some type of learning disability. Epidemics can happen in 10 years, genetic changes to populations require many generations.”

Where is the increase evidenced? Depending on the data, this may or may not be valid, the definition does not attempt to answer for other factors such as change in criteria, increased knowledge, and more precise diagnostic tools. In the 1970s the mean prevalence for autism was (3.27) per 10,000 by the way; if we include the whole autism spectrum then we have 13.7 per 10,000. Also, the present prevalence is probably best described as 1 in 166. While genetic changes take many generations, perhaps knowledge of the various ways of being human take even longer.

Myth 2

“There is a growing body of evidence that children properly treated for mercury poisoning fully recover normal functioning and are indiscernible from their neurotypical peers. Any toxicologist will tell you that mercury poisoning represents a temporary, treatable state. Thorough removal of mercury will resolve most or all of the symptoms. Autism is only life long if mercury poisoning is never treated”

This would be the appropriate time to cite peer reviewed research clearly demonstrating this, this is absent.

Myth 6

“This myth persists despite being refuted by a wide range of scientists, policy makers, and health care organizations. All the available data points to an epidemic. Between 1992-2002, the Department of Education estimates that there has been a 714% increase in the number of autistic children. In the 1970s, autism was estimated to occur in 1 in 25,000 children. Between 1970 and 1990, that number increased to about 1 in 2,500. Today, the CDC acknowledges the number is about 1 in 166, even Eli Lilly, the maker of Thimerosal, says it's 1 in 150. Many believe it is closer to 1 in 125. The anecdotal evidence that we are experiencing an epidemic is overwhelming. If there is no epidemic, then where are all the autistic adults? Ask any doctor, teacher, or day care worker who has been around children for 20 or more years, and they will tell you that the epidemic is unprecedented. What parent, either now or 20 years ago, does not notice that their child who spoke at one year is no longer speaking, or that their child does not respond to their name or look them in the eyes, or is displaying odd, repetitive behaviors like hand-flapping, spinning, and rocking that no other child is doing? Did those parents 20 years ago not notice these things?”

Where is this refuted via research? I have dedicated other posts to why the education data should never have been used to track prevalence or incidence. A Photon In the Darkness (2005) points out that the plural of anecdote is not data. By the way what was the average age of diagnosis twenty years ago; maybe we are not always as good of observers as we think. Also, twenty years ago Autism was a new diagnosis (placed in DSM-III, 1980).

Myth 8

“The symptoms of autism and other neurodevelopmental disorders are identical to the symptoms of mercury poisoning. The rapid rise in the number of these disorders corresponds to the dramatic increase in the amount of Thimerosal (49.6% ethylmercury by weight) given in recommended vaccines to children under two years of age. With the addition of two new vaccines in the early 1990s, the amount of ethylmercury increased 246% with most of this increase being given within the first six months of life when an infant's neural, detoxification, and immune systems are all undergoing rapid development. Equally damaging, the vaccines were given much earlier in a child's life, when the capacity to detoxify is still developing. Numerous studies demonstrate again and again the causal link between neurodevelopmental disorders and mercury, regardless of the source of exposure. Finally and most definitively of all is that when mercury is removed from these children via chelation or other means of detoxification, their symptoms resolve.”

There seems to be important differences, such as the shaking that is seen in mercury poisoning. Again correlation is not causation, there are other correlates as well. No study demonstrates the causal link between autism and mercury, this is in part because, such would never get past an ethics review board. Where is the research?

Myth 15

“You could analyze the data the government maintains through its "Vaccine Adverse Events Reporting System" and compare the data they already have on children who received Thimerosal-containing vaccines against children who did not receive Thimerosal in their vaccines. This study has already been done by Mark & David Geier and showed a high correlation between Thimerosal dosing and neurological disorders:”

Correlation is not causation.

“You could compare the symptoms of mercury poisoning and the symptoms of autism and see how similar they are. This study has already been done and demonstrated that the symptoms of autism and the symptoms of mercury poisoning are exactly the same:”

Except for the instances where they are not similar.

“You could administer a chelating agent to remove heavy metals, including mercury, to a group of autistic children and to a group of neurotypical children and measure the amount of mercury coming out of the children to see if there are any differences. This study has already been done by Jeff Bradstreet and showed that autistic children excrete significantly more mercury than neurotypical children:”

Yes, but that does not mean mercury caused the autism. Also, a more equivalent control sample would have been desirable.

Myth 16
“You could inject a group of mice with Thimerosal in doses that proportionally mimic the timing and amount received according to the recommended vaccination schedule and compare these mice to a control group for neurological development. This study has already been done by Mady Hornig et al. and showed that a subset of mice with genetic detoxification impairments who received Thimerosal injections developed "autistic symptoms":”

To my knowledge we have no protocol for identifying autistic mice.

“You could run a trial of 31 autistic children where you chelated patients over the course of twelve months and had parents videotape their children and test urine and fecal samples for toxic metals every other month. You could then compare the children's progress and symptoms from the beginning to the end of treatment. This study was done by Dr. Rashid Buttar and he made the following statement before Congress.”

The videotape is not sufficient to show causation, this is due to observer drift. This also never made it to a peer reviewed journal.

Myth 16

“Generation Rescue believes autism is an issue of toxicology. Yet, you never hear from a toxicologist saying there is no correlation between autism and mercury. This is because toxicologists know that the link is likely. Hearing a psychiatrist comment on mercury toxicity is like seeking the opinion of a urologist for a new heart procedure. It doesn't make sense to accept the expertise of people who have no experience in the field of heavy metal to.”

Anyone can make a criticism, the criticism has to stand on its own merit. Same goes
for the validity of an experts opinion, it has to stand on its own merit.

Myth 19

“In May 2004, the Institute of Medicine released a 216-page report titled Immunization Safety Review: Vaccines and Autism and concluded that there did not appear to be a causal link between Thimerosal and the autism epidemic. This study was paid for by the CDC, a conflict in of itself, and there is growing evidence that the conclusion was pre-ordained before any research was done. Regarding the potential link between mercury and autism, Dr. Marie McCormick, Committee Chair of the IOM study, in a recently released transcript, stated (before any research had been done), "We are not ever going to come down that it is a true side effect." Much of the IOM's conclusion was based on the aforementioned CDC and Danish studies - there was no primary research done. This lack of new, primary research is a critical point: the IOM's conclusion was largely based on the studies discussed in Myths 17 & 18 above that are controversial flawed.”

Its seems both sets are flawed. The Danish studies are mire by conflicts of interest and the others by lack of scientific rigor. This is inconclusive.

I think covering the other myths would involve me repeating earlier points.

The data so far seem inconclusive either way. For my part I don’t think the thimerosal theory can hold up in the absence of the proposed epidemic; I take the position that there is no epidemic. Maybe, ultimately the ball is back in the court of the advocates of this theory. They will have to conclusively and repeatedly show the effectiveness and safety of chelation using research that demonstrates causation, and publish in peer reviewed journals. They will also have to effectively demonstrate an increase in autism exists, and they will have to deal with the ethical questions that arise from attempting to remove autism from children. Until this is done chelation will remain pseudo-scientific.


A Photon in the darkness. 2005.
Accessed September 6, 2005

Chakrabarti, S., & Fombonne, E. (2001). Pervasive developmental disorders in preschool children. Journal of the American Medical Association, 285, 3093-3099.

Generation Rescue. 2005.
Accessed October 7, 2005.


Blogger Ed in Colorado said...

"In the 1970s the mean prevalence for autism was (3.27) per 10,000 by the way; if we include the whole autism spectrum then we have 13.7 per 10,000. Also, the present prevalence is probably best described as 1 in 166."

If 13.7/10000 is the 1970 rate for the whole autistic spectrum and 1/166 (60/10000) is today's level, then your own statistics say that there is an epidemic today.

You are correct in that there are no peer reviewed repetitions of the measurements done by the researchers cited by Generation Rescue. There will not be. Such measurements would damn the use of thimerosal and will not be done by anyone looking for funding from the IOM, NIH, CDC or any other government medical institution or anyone looking for publication from one of the medical journals. Autism-mercury is sacrilege among the medical priesthood. Anyone who dabbles in it is subject to excommunication.

8:09 PM  
Blogger Interverbal said...

Hi Ed,

Not so long ago, we would be in agreement. I was astounded by the epidemiology data. It clearly showed an upward trend. When I began to look at autism prevalence, if anything I leaned slightly towards the idea of an epidemic.

Then I found out something interesting; the definition and number of subtypes of autism have repeatedly changed over the years. This is a very serious confound. We really can’t say if we are measuring a change in diagnostic criteria/type or if we are seeing an incidence change. Until we achieve a period of diagnostic stability, it is impossible to take any sort of conclusion from change by decade.

I would also add, that folks are more aware of autism now and we have better diagnostic tools than we did even ten years ago. Such things have effects on what we measure.

Previous to 1980, autism was simply a research category. The epi studies were based on what the researcher decided was a good definition for autism. Based on my reading of those studies, I would go so far as to say the strictness of the definitions fluctuated a bit depending on the time period and researcher. I will very likely write about this at some point.

Are you familiar with Multiplex Developmental Disorder? It is a research category, but is considered a type of PDD. There is a fair chance it will end up o the next DSM, which is due about 2011. I really try to keep up on the research, but this was under my radar for quite a while. You can read about it here

I was frustrated when by the lack of Rett’s Disorder epidemiology. It was difficult to find. Now I know that many autism professionals don’t think Rett’s should be listed as a PDD. It could very well be taken off on the next DSM.

That is the way it goes for the DSM, off and on, on and off.

9:15 PM  
Blogger Interverbal said...

Hi again Ed,

Okay, I am looking at the second part of your post.

I doubt we will do any causative research on thimerosal for ethics reasons. That is alright, we can do some research on chelation and make some pretty educated guesses based on that.

Someone could do a multi-element design across subjects (and have just 3 or so subjects) and still show causation for a chelation treatment.

Wouldn’t be as impressive as a big group design logic experiment, but it would show causation and could be used to help justify funding for those big ones from some other organization. That is exactly what I would do.

If nothing else, it would provide a much more robust evidence than anything we have seen yet, and with just three subjects, it is not particularly expensive.

Such a study would probably be able to get in somewhere in a peer reviewed journal. Maybe “Focus on Autism and other Developmental Disorders”. They seem to be able to deal with highly uncontrolled, quasi-experimental findings for GF/CF diets and social stories, I imagine they could choke down a full experimental 3 person design for chelation.

So, why don’t they do this instead?

9:44 PM  
Blogger Ed in Colorado said...

There have actually been a number of interesting measurements concerning mercury and autism. None have come out of the medical research. These include hair sample measurements of newborns, hair sample measurements of autistics vs the normal population, measurements of glutatione levels. The indications of these measurements is that there are certain people (autistics) who do not process mercury the way the rest of us do. But I don't expect any of them to get repeated by the medical community.

8:58 PM  
Blogger Interverbal said...

Hi Ed,

I have read what I could about that research. I thought it was interesting.

This shows differences in mercury level so, yes, something interesting is going on.

This does not show that mercury causes autism, just that there is a correlation.

I learned today that there will be a chelation study in Arizona. I am anxious to see what it shows.

9:44 PM  
Blogger Heather Kuehl said...

How is it possible that with our technology and medical advances that we just dont know if mercury, a known neorotoxin, is correlated or a cause of autism. . Clearly there is not enough research and that in itself poses a problem. How hard would it be to have the gov fund the research, provide unbiased researchers with all the information and get the answers we need to end this debate. Unless there is something we the public aren't sapposed to know. . Sounds fishy to me. until then I guess we will keep injecting our children, which we are sapposed to be protecting, with a known neurotoxin that may or may not be the cause (or correlated to autism)

11:33 AM  
Blogger Interverbal said...

Hi Heather,

Congrats on the new blog.

"How is it possible that with our technology and medical advances that we just dont know if mercury, a known neorotoxin, is correlated or a cause of autism."

I would argue that we do know. The answer seems to be "no". We are down to an ever shrinking possibility that maybe it affects a few kids.

"Clearly there is not enough research and that in itself poses a problem. How hard would it be to have the gov fund the researc"

Oh, but they have... repeatedly.

"provide unbiased researchers with all the information and get the answers we need to end this debate"

Of all the problems, with the current research, I have the least respect for this criticism. I have been involved in the field long enough to remember when the CDC and FDA were seen as the good guys. Funny how times changed.

I wish someone would write an article about how the CDC and FDA were viewed back when the thimerosal hypothesis was actually credible. Before the ranks were infiltrated by believers in homeopathy and other folks who have no use for actual science.

4:16 PM  

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