Friday, July 06, 2007

Study abstract:

“Autism is a developmental disability characterized by severe, pervasive deficits in social interaction, communication and range of interests and activities. The neurobiologic basis of autism is well accepted, although the specific etiology is unknown. It has been theorized that autism may result from a combination of predisposing genes and environmental factors. While autism has a known association with environmental factors such as rubella and valproic acid exposure in utero, other proposed environmental mechanisms such as mercury toxicity or other heavy metal exposure have minimal research support. Despite this fact, interventions including oral and topical chelation therapy are being used to treat autism following evaluation of hair, blood, or urine samples for heavy metal toxicity.
In this study, hair samples were obtained from 15 children with autism between the ages of 2 and 6 years and 16 controls in the same age range who are the siblings of the subjects. The hair samples were obtained according to lab. specifications and submitted in a blind fashion to Doctor's Data Lab. for measurement of mercury levels. Data from the two groups were then compared using T-test. No significant differences were found between mercury levels for the two groups. This study raises questions about the theory that mercury toxicity causes autism and points to the difficulty in quantifying chronic mercury exposure through currently available laboratory measures.”

Notes:

The research was supported in part by a grant from the University of Louisville Pediatric Research Foundation.

Reference

Williams
, G. P., Hersh, J. H., Allard, A., & Sears, L. A. (2007). A controlled study of mercury levels in hair samples of children with autism as compared to their typically developing siblings.

9 Comments:

Blogger Michelle Dawson said...

That paper (Williams et al.) is in press in the journal Research in Autism Spectrum Disorders (in case anyone's wondering).

9:25 PM  
Blogger María Luján said...

Hi Jonathan
The hair can be used only as a clue. Even more, this kind of studies are much more useful, IMO.
Magnes Res. 2006 Mar;19(1):35-45.

Contents of bioelements and toxic metals in the Polish population determined by hair analysis. Part 1. Children aged 1 to 10 years.Dunicz-Sokolowska A, Radomska K, Długaszek M, Graczyk A.
Polish Academy of Sciences, System Research Institute, ul. Newelska 6, 01-447 Warsaw, Poland.
The aim of this study is to define referential values of 5 basic bioelements (Ca, Mg, Zn, Cu, Fe) and toxic metals (Pb and Cd) in the hair of Polish children aged 1 to 10 years, based on the research conducted from 1991 to 2004 on a group of over 4000 formally healthy children. Significant differences between girls' and boys' hair Ca, Mg and Zn were observed, particularly in those aged 7 to 10 years (p = 0.0000). We noticed that boys have less concentration of hair Ca, Mg and Zn than girls do. Maximum concentration of hair Fe in children of both sexes was observed in 3 to 5 years old, diminishing subsequently. No significant differences were observed between concentrations of Cu in the hair of girls and boys of the same age, in the tested period from 1 to 10 years of age. The greatest amounts of Pb and Cd characterize the youngest children aged 1 to 5 years; while the boys possess a tendency to have higher contents of toxic elements than do girls. Children whose concentrations of hair bioelements have shown values outlying from reference ranges and who have higher concentrations of toxic metals should undergo further diagnostic tests since the results of previous tests could be a sign of disturbances in their organism leading to various diseases. The analysis of concentrations of bioelements and toxic metals in organisms based on hair analysis can be useful as a convenient, non-invasive and painless method of diagnosis of pathological states. In combination with other analytical data, this method is a complementary diagnostic procedure for practicing physicians.

There have been no studies on the transport/excretion of toxic/essential elements in autism.

10:05 PM  
Anonymous chaoticidealism said...

Isn't it generally stated that the mercury exposure that causes autism is a low level, lower than that needed to cause the classic symptoms of heavy-metal poisoning? If so, mercury may not show up in the hair at any greater level than normal... especially if normal levels of mercury trigger abnormal biology caused by a predisposition to autism.

Essentially: Mercury-poisoning is a theory which claims it needs no proof...

8:33 AM  
Blogger Interverbal said...

Good note Michelle, the full citation will be added when it comes out.

Maria, I agree with you. It looks like hair analysis is only a blunt tool. However as long as the tool was reliable between the two groups, the study findings could still be argued to be valid.

9:51 AM  
Blogger Interverbal said...

"Isn't it generally stated that the mercury exposure that causes autism is a low level, lower than that needed to cause the classic symptoms of heavy-metal poisoning?"

Yes, and that the children who develop autism because of it, were sensitive to it in the first place.

"Essentially: Mercury-poisoning is a theory which claims it needs no proof..."

If it claims it needs no proof then it is faith, not science. Also, if a theory can not be potentially falsified, it again falls into the faith category.

I think some would indeed take that position. However, I also think others would try to justify the theory based on supposed treatment effects i.e. (We chelated our child and he began speaking, ergo the mercury caused his autism). And I think others would appeal to research (at varying qualities) to try to justify the theory.

10:02 AM  
Blogger daedalus2u said...

If "normal" levels of mercury cause autism, why can't "normal" levels of something else cause it too?

10:19 AM  
Blogger MJ said...

I was under the impression that heavy metals such as mercury were excreted into the hair and other body substances at the time of the exposure as the body clears the substance. (please correct me if I am mistaken)

So looking at the mercury levels in the hair of a two to six year old whom presumably has had their hair cut several times will only show exposure to mercury during the time frame since the last hair cut.

So I am unclear on what this study is trying to demonstrate. Is it testing to see if autistic children have a continuing exposure to mercury?

10:11 AM  
Blogger Interverbal said...

Hi MJ,

Excellent question.

The authors of this paper seem to be operating under the premise that heavy metal exposure even in the past should result in a higher excretion rate in the hair in the present.

It is worthwhile noting that these authors are not alone in this assumption and other have also conducted autism, hair, mercury level research, on both sides of the debate.

If it is true that autistics are poor excretors of heavy metals (and maybe even if they are not) then this is a real concern. I just haven't seen a definitive answer on this issue. It might be there, but if so, I am ignorant of it.

4:45 PM  
Anonymous Regan said...

Hi,
I actually read the full text earlier this evening and I think that what they are saying is contrary from what seems to be assumed from the abstract, to wit, this paper pointed out weaknesses in the paper by Bernard, et. al (2001), various citations that do not support a mercury-poisoning/autism hypothesis, and the strengths of blood and urine for acute exposure/weakness for chronic exposure and the various analysis issues related to hair determinations.

"Hair samples were analyzed for 15 children with autism and 16 controls. There was no significant difference in age of participants and controls. The majority of participants and controls were male (100% of participants and 75% of controls). Mean mercury value for controls was 0.085 μg/g (S.D. of 0.07) and for participants was 0.07 μg/g (S.D. of 0.06). T-test yielded a value of 0.62, indicating no statistically significant difference between the groups.
...
This study is unique in comparing children with autism to siblings who would likely have had similar environmental exposures. Our results did not demonstrate any statistically significant difference in levels of mercury in hair analyses for these two groups. This finding supports the previous results of Ip et al. (2004), only one of two other studies looking at mercury levels measured through hair analysis in this population. While the study is limited by the small number of participants, the results call into question the validity of hair analysis as a means of measuring mercury exposure in patients with autism. In addition, findings cast further doubt on theories which propose mercury as an etiologic agent in this complex developmental disorder. Concerns regarding implementation of treatment strategies such as chelation therapy based on limited and conflicting data are important to share with parents as they look at alternative interventions for the treatment of autism. "

Williams, P.G., Hersh, J.H., Allard, A, Sears, LL. (2008). A controlled study of mercury levels in hair samples of children with autism as compared to their typically developing siblings. Research in Autism Spectrum Disorders, 2(1):170-175.

7:12 AM  

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