Tuesday, February 24, 2009

Mercury challenge misunderstandings: A guide especially for parents new to autism

Making decisions as a parent of a child diagnosed with autism can be tough. This doesn’t mean it has to be, just that it can be. One of the reasons it can be tough is that popular culture or the internet will bombard you with a variety of education plans, treatments, or therapies, many of which will claim to be scientifically proven or evidence based, but very few of which even come close.

One of the popular theories in the US, is that autism is caused by one or more forms of mercury. Where the mercury comes from depends on who you talk to, vaccines, dental fillings, fish, lights, computer screens, forest fires, and cremations have all been named as suspect. That may seem tricky enough, but the real question is in how children diagnosed with autism deal with the mercury.

Some sources claim that children diagnosed with autism are poor excretors of mercury. In other words for some reason they don’t get rid of the mercury their body accumulates (either in a fast or slow way) and that it poisons them and results in autism. For this group the advocates claim that mercury poisoning is difficult to assess. They may recommend assessing other biological factors as evidence. Or they may recommend a challenge (provoked) test for mercury.

Just to be clear, a provoked test is when a chelating agent is given to the patient and then the mercury test is administered. Some chelating agents bind to mercury and/or other heavy metals making it much more likely that they will be cleared from the body. This step is important for advocates of the poor excretor hypothesis, because they argue that the chelating agent captures mercury in the body. An increase between a non-provoked test and a provoked test is evidence of this according to certain parties. Or even without this non-provoked test, a provoked test that comes back in an elevated range can be evidence of this all by itself. However, others who advocate a mercury etiology of autism theory do not seem to put stock in the poor excretor theory. They advocate straightforward testing without a provoked test.

For a parent considering heavy metals testing a good first step is to decide which variant you believe in. These theories cannot both be true, they are exclusive. Children with autism are either poor excretors or they are not. And while some might try to be ingenious and claim that sometimes it is one and sometimes it is the other, I would ask the reader to decide whether this is truly a valid argument.


If a parent decides that the poor excretor hypothesis is unlikely, then there is no need for a provoked test.

If on the other hand a parent decides the poor excretor hypothesis is valid then a provoked test may seem reasonable. This is where my concerns begin.

My core concern is this; there is no mercury scale that was normalized with participants who were first given a provoking agent. This means that any of the provoked measurement will have to be compared to a scale established only with non-provoked samples. This is innately invalid, and yes, invalid is the right word here.

This is why: When one wants to establish a statistical scale, one must first create the conditions under which data will be collected. After data are collected a mean (average) is determined as is the standard deviation, which is simply a statistical way of determining how far away (in either direction) a given score is from the average. However, if you try to compare a given score taken under different conditions from how the scale was formed, it is no longer meaningful.


These data taken under different conditions were not included when the mean or standard deviations were calculated. For them there is neither mean nor standard deviation. The comparison is meaningless, and there is no way right to compensate for this problem at the moment. And while this may be a standard practice for many labs and practitioners, anyone who tells you these tests can be used to determine mercury poisoning is not using any recognized standard of science or statistics.

If you are a parent please be aware of these facts when you consider a provoked test.

11 Comments:

Blogger MJ said...

Good writeup. In general I would have to agree with you but there is one point that I would argue:

These theories cannot both be true, they are exclusive

I think that both theories could be true, just not in the same person. It is entirely plausible and I would even say likely that there are different types of autism complete with their own disparate causes.

So it is possible that one group of people with autism have problems eliminating mercury from their bodies while a different group does not.

The other thing is that while what you say is true I am still not sure what you would suggest as an alternative test.

6:14 PM  
Blogger Do'C said...

"So it is possible that one group of people with autism have problems eliminating mercury from their bodies while a different group does not."

Sure that's possible. It's also possible that the Loch Ness Monster is real.

Evidence for either, is very weak to non-existent.(1)

Even if such a group among autistic people were identified, correlation doesn't equal causation.

5:28 PM  
Blogger MJ said...

So what you are saying is you believe in the Loch Ness monster?

Seriously, the lack of a testing mechanism puts a large damper on being able to directly address the theory. If you don't have have a way of measuring something you cannot say that it isn't there. In the same token you can't say that it is there either - the best you can say is you don't really know.

Lack of evidence != false.

If you want to put the theory to rest you disprove it. You don't keep repeating that there is no evidence that it is true.

As far as the correlation argument that is an often cited bit of nonsense.

Of course correlation does not equal causation.

But correlation is one the required steps along the way to establishing causation. All things else being equal two variables that are correlated have more of a relationship to each other or another variable than two variables that are show no correlation.

So IF (big if) there was a subgroup of people with autism that had issues eliminating heavy metals from their bodies that would likely be significant.

The whole theory rests on a reliable way of measuring mercury in the body. And to the best of my knowledge there is no good way to do that.

8:40 PM  
Blogger Interverbal said...

Hi MJ,

Sorry this took me a while.

“I think that both theories could be true, just not in the same person. It is entirely plausible and I would even say likely that there are different types of autism complete with their own disparate causes.”

While this is possible, it looks much more likely that it is just an excuse to discount one research type or another. It smacks of an excuse to reject inconvenient findings.

“So it is possible that one group of people with autism have problems eliminating mercury from their bodies while a different group does not.”

And….. that in both cases it leads to a condition that is either autism or indistinguishable from autism. That seems to be the argument.

“The other thing is that while what you say is true I am still not sure what you would suggest as an alternative test. “

I wouldn’t suggest another test. This problem is not currently addressable. That is frustrating, because I don’t see a solution to the problem…. only the nature of the problem. Maybe the advocates of the poor excretor theory can fund some research that leads to the develop of a provoked scale for mercury.

8:53 PM  
Blogger MJ said...

Interverbal,

And….. that in both cases it leads to a condition that is either autism or indistinguishable from autism. That seems to be the argument.

I think this is where we are heading - not one autism but different conditions that "look" like autism. And since all we have to diagnose now is how it "looks" there is no good way to tell the them apart.

I have seen some recent research that seems to be pointing in this direction and it would go a long way to explaining why it is so difficult to pin down what exactly is going on in autism.

I wouldn’t suggest another test. This problem is not currently addressable. That is frustrating, because I don’t see a solution to the problem…. only the nature of the problem.

That is along the lines of what I thought. I wanted to make sure that I understood what you were saying and that I was not missing something.

Thanks for the answer.

8:59 AM  
Blogger Do'C said...

"If you want to put the theory to rest you disprove it. You don't keep repeating that there is no evidence that it is true."

If we're going to talk scientific methodology, let's be wholly accurate. Impaired "mercury efflux" is a hypothesis. As a hypothesis it completely lacks scientific support. There is absolutely no need to "disprove" a hypothesis for which there isn't scientific support, or at the very least, evidence that suggests the hypothesis should be investigated (e.g. studies showing that autistic children actually have impaired mercury excretion).

From a scientific perspective, serious investigation into this hypothesis wouldn't be much more than responding to urban legend that appears to have started with Holmes et al.

Holmes et al. put the hypothesis forth based on a gigantic "if" which lacks scientific/medical merit.

In short, there isn't anything TO disprove.

11:05 AM  
Blogger Interverbal said...

Hi MJ,

"I think this is where we are heading - not one autism but different conditions that "look" like autism. And since all we have to diagnose now is how it "looks" there is no good way to tell the them apart."

Provided that they exist at all. Some folks (not anyone here per se) often treat the multi-causation theory of autism as if it were a new revelation. It is not, it goes back 30+ years. People were debating this in the
70s.

"I have seen some recent research that seems to be pointing in this direction and it would go a long way to explaining why it is so difficult to pin down what exactly is going on in autism."

If I go abstract diving I can probably find something that vaguely suggests this. However, there is no direct evidence of this from what I can tell.

Also, I want to address something you said to Do'C:

"If you don't have have a way of measuring something you cannot say that it isn't there. In the same token you can't say that it is there either - the best you can say is you don't really know."

You are not the first person to make this point. It has been made by many people over the years. However, I take issue with this line of reasoning in general. I would argue that what we should do in an unclear case.... depends on the quality of evidence.

Evidently millions of people (if you accept some shoddy overgeneralized demongraphics) report having been abducted by aliens. I lack the time and interest to be able to address each and every anecdote. Must I therefore maintain a rigid agnosticism in regard to alien abduction? I think doing such would be illogical.

What I can do instead is say that the evidence for such appears to be lacking and that there appears to no validity to the claim. However, I must also accept that if this were to change than I would have to revise my position.

My position is very similar for autism and vaccines at this time. It could change tomorrow if new evidence emerges.

2:15 PM  
Blogger MJ said...

From a scientific perspective, serious investigation into this hypothesis wouldn't be much more than responding to urban legend that appears to have started with Holmes et al.

I was not talking about a strictly scientific perspective. People believe that there is a link. If you want to convince them that there isn't one then you prove it doesn't exist. You don't say there is no reason to look at the question since there is no evidence that the problem exists.

Some folks (not anyone here per se) often treat the multi-causation theory of autism as if it were a new revelation. It is not, it goes back 30+ years.

I was not aware of the theory going back that far although I know it has been around for a little while. I would have thought that in 30 years the question would be further advanced than this.

If I go abstract diving I can probably find something that vaguely suggests this. However, there is no direct evidence of this from what I can tell.

Actually it was more than that. Here is one example :

http://www.ncbi.nlm.nih.gov/pubmed/17275283

Not direct evidence but still interesting, at least to me.

I would argue that what we should do in an unclear case.... depends on the quality of evidence.
...
Evidently millions of people (if you accept some shoddy overgeneralized demongraphics) report having been abducted by aliens.


Really, alien abduction? That is how credible you find theories linking mercury exposure to autism? First it was Do'C with Lock Ness and now you with alien abduction.

I would suggest that when there is a lack of evidence that you can evaluate for yourself your opinion is not based on the merits of argument but rather on how trustworthy and believable you feel the other party is. The question becomes will you accept their judgment as your own.

5:44 PM  
Blogger Interverbal said...

Hi MJ,

“I was not aware of the theory going back that far although I know it has been around for a little while. I would have thought that in 30 years the question would be further advanced than this.”

I agree that it is surprising. I also think that far from being enlightened, we continue to be in the “dark age” in regards to autism. The one thing that has gotten better is belief in educational efficacy for person meeting criteria for autism. In the 70s it was still at least partially acceptable to question whether autistics would really benefit from formal schooling. That has something that has changed. I give a lot of credit to TEACCH for changing this view in regards to public school teacher’s attitudes.

The other thing that is surprising in old research is the attempt to draw a connection between autism and schizophrenia (or at least fail to distinguish between them). This occurs almost non-stop pre 1990. It happens again and again and again and again….. The only groups who really avoid this are the speech paths and OTs. However, there is relatively little research literature for both specific to autism (but there is indeed some).

“Actually it was more than that.”

Not really, the article you cited is an opinion piece.

“Really, alien abduction? That is how credible you find theories linking mercury exposure to autism? First it was Do'C with Lock Ness and now you with alien abduction.”

No, I find the vaccine etiology theory to be much more likely. I gave the aliens example just to offer an extreme example to help illustrate the problem I see. Namely, that anecdote is not enough….. not nearly enough.

“I would suggest that when there is a lack of evidence that you can evaluate for yourself your opinion is not based on the merits of argument but rather on how trustworthy and believable you feel the other party is. The question becomes will you accept their judgment as your own.”

I am not going to assign the worth of an argument based on how trustworthy I think another party is. Instead I will looks at the claims in relation to evidence to contrary. This is the path I select to pursue.

9:01 AM  
Anonymous passionlessDrone said...

Hi Interverbal -

But we have a scale. Zero.

You may remember that you did a write up of the Soden paper; wherein fifteen children were administered a challenge test, I think twelve kids with autism and three controls. Strangely enough, the researchers were unable to detect any mercury at all in twelve of the children measured.

Of course, if Soden used a benchmark that was too high, everything underneath that limit woudl be reported as undetectable. Either Soden was right, and most people don't excrete mercury even when challenged, or Soden used poor methodology on which to form conclusions. I have had it suggested to me that children may be supplemented previous to challenge with mercury containing mixtures. Possible, but highly speculative.

I think we need to keep in mind there may be a small percentage of children with autism for whom mercury is a big issue. If I recall correctly the details of the DeSoto debacle, two of the children with autism in a group of about 80 were kicked out, because their mercury levels were three standard deviations high. We should have had to sample well over three hundred kids to get even a single value that high. Doesn't having two values in this range tell us that either we had a very, very coincidental sampling, or perhaps, we are sampling two groups and pushing them together when they should not be?

Unfortunately, even with such a potential subgroup, a challenge test may not provide useful information for the reasons you detail.

I am pleased to see you blogging again.

- pD

6:31 PM  
Blogger Interverbal said...

Hi PD,

"Strangely enough, the researchers were unable to detect any mercury at all in twelve of the children measured."

True,

"Either Soden was right, and most people don't excrete mercury even when challenged, or Soden used poor methodology on which to form conclusions."

Or he used too little DMSA

"If I recall correctly the details of the DeSoto debacle, two of the children with autism in a group of about 80 were kicked out, because their mercury levels were three standard deviations high."

Yes, that was what DeSoto did in her reanalysis. Also, I don't remember which outliers were in which group, but the effect of keeping the outliers in the analysis was toward finding no association.

12:10 PM  

Post a Comment

Links to this post:

Create a Link

<< Home