News and Notes about Scientific Research on Autism and other Developmental and Behavioral Disorders

Editor: Bill Ahearn, Ph.D., BCBA
Director of Research, New England Center for Children

Thimerosal and Autism

The Boston Globe and Rolling Stone magazine recently published an article written by Robert F. Kennedy Jr. accusing the U.S. government of concealing evidence linking thimerosal-containing vaccines to autism. As reported in our previous newsletters, there has been no scientific evidence establishing a link between vaccines and autism. Thimerosal is a preservative that has been used in some vaccines since the 1930s (CDC, retrieved June 2005). Thimerosal consists of 49% ethylmercury and some have suggested, partly because of the known effects of methylmercury (an environmental contaminant often found in fish) as a toxic substance, that thimerosal delivered in vaccines causes autism to develop in some children. Much is known about the effects of the more dangerous methylmercury. In the developing child, massive systemic damage can occur through excessive methylmercury exposure. The Food and Drug Administration (EPA, retrieved June 2005) has advised pregnant women, nursing mothers, and young children limit their intake of certain types of fish, like tuna, that tend to contain high levels of methylmercury in order to prevent excessive methylmercury consumption.

Much less is known about ethylmercury, however, the CDC reports that the cumulative exposure to ethylmercury that occurred when thimerosal was used as a preservative in vaccines was less than the FDA and World Health Organization recommended maximum safe exposure to methylmercury. However, the Environmental Protection Agency’s more stringent guideline for methylmercury exposure was exceeded. Therefore, given the heightened concern over mercury exposure, the suggested link between thimerosal and autism, and technology that exists for eliminating ethylmercury from vaccines, thimerosal has been removed from all vaccines in the U.S. with the exception of certain flu vaccines.

But is there evidence for thimerosal causing autism? The most definitive study to date was conducted by Danish researchers (Hviid et al., 2003). It looked at thousands of children who received either vaccines containing thimerosal or vaccines without this preservative and found that the rates of autism were identical in the two groups. If thimerosal was causing autism, a difference should have been found. Thimerosal had been removed from the vaccines of other developed countries such as Canada and Denmark prior to it being removed from vaccines in the U.S., however, no decrease in the prevalence of autism has been detected in these countries (NYTimes, retrieved 06/25/05). In 2003 the American Academy of Pediatrics, an organization that called for the removal of thimerosal from vaccines in July 1999, summarizes the evidence of harm from it as follows, “No scientific data link thimerosal used as a preservative in vaccines with any pediatric neurologic disorder, including autism. Despite this, the Centers for Disease Control and Prevention, American Academy of Pediatrics, National Institutes of Health, and US Public Health Service have continued to investigate this issue to put theoretic concerns about this mercury-containing compound to rest.”

The article written by Robert Kennedy is irresponsible and unfounded. Particularly concerning is the lack of accuracy in the presented evidence. The following disclaimer has been posted (on June 20, 2005) on the Rolling Stone website acknowledging some of these inaccuracies:

“NOTE: This story has been updated to correct several inaccuracies in the original, published version. As originally reported, American preschoolers received only three vaccinations before 1989, but the article failed to note that they were innoculated a total of eleven times with those vaccines, including boosters. The article also misstated the level of ethylmercury received by infants injected with all their shots by the age of six months. It was 187 micrograms - an amount forty percent, not 187 times, greater than the EPA's limit for daily exposure to methylmercury. Finally, because of an editing error, the article misstated the contents of the rotavirus vaccine approved by the CDC. It did not contain thimerosal. Salon and Rolling Stone regret the errors.

An earlier version of this story stated that the Institute of Medicine convened a second panel to review the work of the Immunization Safety Review Committee that had found no evidence of a link between thimerosal and autism. In fact, the IOM convened the second panel to address continuing concerns about the Vaccine Safety Datalink Data Sharing program, including those raised by critics of the IOM's earlier work. But the panel was not charged with reviewing the committee's findings. The story also inadvertently omitted a word and transposed two sentences in a quote by Dr. John Clements, and incorrectly stated that Dr. Sam Katz held a patent with Merck on the measles vaccine. In fact, Dr. Katz was part of a team that developed the vaccine and brought it to licensure, but he never held the patent. Salon and Rolling Stone regret the errors.”

Within the next couple of years, a definitive answer to whether thimerosal is linked to autism should be at hand. If thimerosal causes autism, then the prevalence of autism should dramatically decline. The empirical evidence on the cause(s) of autism implicate other sources (see Summer 2003 Research Newsletter) and it is not unlikely that the prevalence of autism spectrum disorders will continue to increase. It might be the case that the true prevalence of autism is higher than the current best estimates (Wing & Potter, 2002).

Ahearn, W.H. (May-June 2003). What causes autism? http://www.necc.org/research/newsletter_may_june_2003.asp.

American Academy of Pediatrics (May 16, 2003, retrieved June 15, 2005). Study fails to show a
connection between thimerosal and autism. http://www.aap.org/profed/thimaut-may03.htm.

Center for Disease Control (retrieved June 2005). Mercury and Vaccines (Thimerosal).
http://www.cdc.gov/nip/vacsafe/concerns/thimerosal/.

Environmental Protection Agency (retrieved June 2005). What you need to know about mercury
in fish and shellfish. http://www.epa.gov/waterscience/fishadvice/advice.html.

Hviid, A, Stellfeld, M, Wohlfahrt, J, & Melbye, M. (2003). Association between
thimerosal-containing vaccine and autism. Journal of the American Medical Association,
290, 1763-1766.

New York Times – Harris, G., & O’Connor, A. (June 25, 2005). On autism’s cause, it’s parents
vs. research. http://www.nytimes.com/2005/06/25/science/25autism.html.

Wing, L. & Potter, D. (2002). The epidemiology of autistic spectrum disorders: Is the prevalence rising? Mental Retardation and Developmental Disabilities Research Reviews, 8(3), 151-161.

Readers' Forum

Email your questions to William Ahearn.

Q: I have heard that mercury causes autism. What evidence is there that removing mercury from a child’s body or chelation will be an effective therapy?

A: Mercury detoxification, or chelation therapy, is a controversial therapy that has been suggested as a useful intervention for many conditions. Chelation therapy involves injecting an amino acid, EDTA, into the body. EDTA then binds with heavy metals, like mercury, and allows the body to excrete them. However, chelation is only effective for true heavy metal poisoning. Many have suggested that chelation is effective in treating arteriosclerosis but the American Heart Association (AHA, retrieved June 2005) states that there is no empirical evidence supporting this treatment. They also list several deleterious side effects possible with chelation including kidney failure, convulsions, shock, and heart and breathing difficulties. Several persons have also died while undergoing chelation. Chelation as a treatment for autism stems from the notion that autism is caused by mercury in vaccines. The New York Times (June 25, 2005) reports that, “One of the first to advocate treating autism with chelation and other therapies was Dr. Stephen Edelson of Atlanta…Dr. Edelson said he placed children in 160-degree saunas as part of their treatment. Some children fought to get out of the sauna and kicked out its window, an assistant said in a sworn statement. The doctor said he also used chelation and prescribed 60 to 70 supplements a day, causing some children to vomit.” Dr. Edelson no longer practices medicine following a state medical board censure and lawsuits have been filed against him after several patients regressed significantly under his care. More importantly, there is no evidence that autism is caused by mercury in vaccines and therefore the rationale for chelation therapy for autism is baseless (Quackwatch, retrieved June 2005). In fact, a study conducted at Rochester University found that children given vaccines with thimerosal had levels of mercury in their blood well below levels estimated to be safe (Pinchero et al., 2002). The study also showed that the children excreted the ethylmercury from the vaccines rapidly. This implies that there would be no excessive mercury to remove through chelation.

American Heart Association (retrieved June 2005). Questions and answers about chelation
therapy. http://www.americanheart.org/presenter.jhtml?identifier=3000843.

New York Times – Harris, G. & O’Connor, A. (June 25, 2005). Experts reject some therapies.
http://www.nytimes.com/2005/06/25/science/25treat.html.

Pinchero, M., Cernichiari, E., Lopreiato, J. & Treanor, J. (2002). Mercury concentrations and
metabolism in infants receiving vaccines containing thiomersal: a descriptive study.
Lancet, 360, 1737-1741.

Quackwatch (posted 4/30/2005, retrieved June 2005). Misconceptions about immunization.
http://www.quackwatch.org/03HealthPromotion/immu/thimerosal.html.

Research at NECC

Editor’s note: The New England Center for Children was recently honored to receive the Society for the Advancement of Behavior Analysis’s Enduring Programmatic Contribution to Behavior Analysis award at May’s Association for Behavior Analysis’s annual international meeting. This award represents recognition from our peers of the many accomplishments of NECC. An announcement for the award acceptance speech is provided below.

2005 Award for Enduring Programmatic Contributions in Behavior Analysis:

The New England Center for Children

The New England Center for Children (www.necc.org), founded in 1975, is a private, non-profit organization providing a full range of educational, residential and treatment programs for more than 250 children with autism and related disabilities based on the principles of behavior analysis.

Our mission has three components:

1. To maximize the independence of every student as measured by rates of skill acquisition, performance on assessments, reduction of aberrant behaviors, and transitions to less restrictive environments.

2. To share our work through research, professional development, consultation and dissemination of curriculum. We have published more than 150 research articles, operate six partner classrooms in area public schools, and consult with more than 30 others. Over the last 10 years, 550 of our employees have earned their master’s degree at one of three on-site graduate programs offered at NECC.

3. To secure the financial future of the organization through prudent fiscal management, professional fundraising, tax-exempt financing, and development of diverse income streams.

Our repertoire, which emphasizes skill acquisition, errorless teaching techniques, and function-based treatment, was shaped by our close collaboration with senior behavior analysts including Paul Touchette, Murray Sidman, Gina Green, Richard Foxx, Brian Iwata, and Bill Dube. Mr. Strully and Ms. Foster will give a presentation titled Science and Autism: Translating Research into Practice:

The New England Center for Children attributes its success in the treatment of children with autism to a reliance on the experimental and applied research generated by our colleagues. NECC has a rich behavioral heritage beginning with Paul Touchette and Murray Sidman, who encouraged us to sustain a rigorous adherence to the methodology of ABA. Although this rigor is difficult to maintain, we continuously strive to avoid the temptation to drift away from the fundamentals of data based decision-making. At NECC the influence of both experimental and applied research translates across clinical treatment, staff development and organizational management. Autism responds to sophisticated scientific interventions, not politically correct bromides. If we abandon the methodology of our science, we condemn our children to an uncertain future. We believe success is measured not only by outcome but also by replication of proven methods across public and private settings, and by worldwide dissemination of best clinical practice.

Editor’s note: The New England Center for Children was also honored to be invited to address our colleagues in the autism special interest group at ABA. An abstract of this presentation is provided below.

ABA and Autism: An Unfinished Agenda
Chair: Jack Scott (Florida Atlantic University)
Presenters: William H. Ahearn and Rebecca P. F. MacDonald

The success behavior analysts have had in treating individuals with autism has had a substantial impact on our membership and has led to a much wider profile for our discipline. However, many challenges and obstacles face us that we have either not met or that we choose to ignore. Though agencies, such as the National Institute of Mental Health, acknowledge ABA as an empirically based effective intervention, they also state that there is no single best treatment option for children with autism. Prominent members of the autism community often criticize ABA as; not addressing social functioning, failing to establish dramatic play skills, incapable of establishing a theory of mind, and of creating children with robotic responding that lacks spontaneity. Other more practical critiques state that it is unclear what the effective components of ABA are, how many hours of service delivery are necessary to achieve gains, and what setting ABA services should be delivered in. The main purpose of this presentation is to describe what is necessary for ABA to address these criticisms. Among the recommended courses of action we will describe the importance of local, regional, and national advocacy and public relations.

Editor’s note: The New England Center for Children was also honored to be invited to address our colleagues in the autism special interest group at ABA. An abstract of this presentation is provided below.

Web Resources

For information about The New England Center or to access and electronic version of this or previous NECC Research Newsletters, visit our Web site www.necc.org.

For information about autism, visit the National Library of Medicine s autism site www.nlm.nih.gov/medlineplus/autism.html.

For information about applied behavior analysis in the treatment for autism visit www.behavior.org.

For science-based information on biomedical treatments and theories in autism visit www.autism-biomed.org.

For information on health issues in general visit the World Health Organization www.who.int.

For professionally-screened information on health care (including some treatments for autism and other developmental disabilities), visit www.quackwatch.com.

For information on the Berkshire Association for Behavior Analysis and Therapy, visit www.karsina.us/babat/.

For information on the Association for Behavior Analysis, visit www.abainternational.org.

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