Autism-chelation study canceled.

In September 2008, the National Institute of Mental Health canceled a scheduled trail that was designed to evaluate succimer (DMSA) chelation therapy as a treatment for autism. The trial would have tested the hypothesis that mercury exposure contributes to autism, according to MedPage Today. Researchers would have recruited 120 autistic children, ages four to ten years, "with detectable but not toxic levels of mercury or lead in their blood." The FDA has already approved succimer as a treatment for lead toxicity. NIMH decided to pull the study because of a 2007 rat study, conducted by Diane E. Stangle and collegues. That trial showed that succimer chelation causes "lasting and pervasive cognitive and affective dysfunction, comparable in magnitude to [the dysfunction caused by lead exposure]" (Environmental Health Perspective; February 2007). These findings raised concern that children in the study, who had low levels of lead or mercury, would be harmed by succimer. An NIMH review board decided that "... there was no clear benefit to the children who would participate in the chelation trail and that the study presents more than a minimal risk." Instead of pursuing further data collection and review, which would have taken about four more years, NIMH decided to cancel the study: "During those four years, it is quite likely that additional research on the basic pathology of autism will provide deeper understanding of the causes of autism and more refined avenues for developing treatments."

The NIMH cancellation of this chelation therapy trial is puzzling. First, the rat study "provides clear evidence" that succimer chelation relieves cognitive and behavioral problems in rats with lead toxicity, according to its researchers. In addition, the cognitive and affective dysfunctions in lead-exposed rats parallel the dysfunctions found in children with lead toxicity. Stangle and colleagues conclude: "The present findings thus suggest that if a succimer treatment protocol that produced a substantial removal of [lead] from the brain could be identified for humans, a functional benefit might be derived." The researchers, however, were concerned to find that succimer caused adverse effects in normal rats-that is, rats with no exposure to lead and no sign of dysfunction. The NIMH study did not have a cohort of metal-free children in its design.

According to the NIMH study's design, recruited children would have had a diagnosis of autism and blood mercury levels of 0.1 to 44 mcg/dL or blood lead of 0.1 to 10 mcg/dL. "The upper bounds are the accepted thresholds for toxicity requirements," according to MedPage Today. This statement is not accurate, according to the Risk Assessment Information System (RAIS) from the Department of Energy's Office of Environmental Management. In RAIS toxicity summaries for mercury and lead, symptoms of CNS toxicity becomes noticeable at about 10 mcg/dL of mercury and 30 mcg/dL of lead. The site says that "... toxicity values presented in these toxicity profiles ... are subject to change." In the case of lead,"... no clear threshold is evident."

Another problem with NIMH's decision is that it ignores research on toxic metals in tissue other than blood. A June 2007 study, for example, found that the baby teeth of children with autism spectrum disorder have "significantly (2.1-fold) higher levels of mercury that similar levels of lead and ... zinc" compared to the baby teeth of "typically developing children." These Arizona State University researchers say, "Baby teeth are a good measure of cumulative exposure to toxic metals during fetal development and early infancy, so this study suggests that children with autism had a higher body burden of mercury during fetal/infant development." Hair mineral analysis is another way to gauge metal toxicity. Several studies, including a 2003 study sponsored by SafeMinds, have found lower levels of mercury in hair samples belonging to children with autism: "Hair mercury levels in the autistic group [n = 94] were 0.47 ppm versus 3.63 ppm in controls [n = 45]." The mothers of children in the autistic group "had significantly greater exposure to mercury from amalgam filings and thimerosal-containing Rho D immunoglobulin injections than did a control group." Other studies with similar findings have resulted in a hypothesis that some autistic children excrete heavy metals as efficiently as unaffected children.

Another puzzling aspect about the NIMH decision is that many parents have already reported positive results with chelation therapy. In response to the study's cancellation, Talk About Curing Autism, a support and advocacy group, stated: "Anecdotally, Talk About Curing Autism has either seen or heard of thousands of children [who] have had many of their autistic symptoms decrease due to this therapy. Bu discontinuing this study, the NIMH will not prove the effectiveness of chelation therapy one way or another." Parents will continue to seek chelation for their children, and health authorities can continue to say that no scientific evidence supports its use-simply because no government-sponsored study has been performed.

Adams AJ. Elemental hair analysis test for heavy metal toxicity and mineral deficiencies. The Patients' Voice. Spring/Summer 2008:6,8. Available at: www.pfamhealth.net.

Adams JB, Romdalvik J, Ramanulam VM, Legator MS. Mercury, lead, and zinc in baby teeth of children with autism versus controls. (abstract)/Toxical Environ Health A. 2007 Jun; 70(12):1046-51. Available at: www.ncbi.hlm.nih.gov/pubmed/17497416. Accessed October 27, 2008.

Gever J. NIMH cancels autism chelation trial. MedPage Today, September 19, 2008. Available at: www.medpagetoday.com/neurology/autism/tb/10979. Accessed October 13, 2008.

Holmes AS, Blaxill MF, Haley BE. Reduced levels of mercury in first baby haricuts of autistic children. (abstract) Int J Toxical. 2003 Jul-Aug:22(4):277-85. Available at: www.necbi.nlm.nih.giv/pubmed/12933322. Accessed October 27, 2008.

Meletis CD; Zabriskie N. Is autism the coal miner's canary of America's health status? The Patients' Voice. Spring/Summer 2008:5,7. Available at: www.pfamhealth.net.

Stangle DE, Smith DR, Beaudin SA, Strawderman SM, Levitsky DA, Strupp BJ. Succimer chelation improves learning, attention, and arousal regulation in lead-exposed rats but produces lasting cognitive impairment in the absence of lead exposure. Environmental Health Perspectives. February 2007;115(2): 201-209. Available at: www.ehponline.org/members/2006/9263/9263.pdf. Accessed October 13, 2008.