Autism is neurological disorder in which the brain does not function properly in the areas of social interaction and communication skills. Autism patients tend to show symptoms of slow speech and difficulty engaging in activities. As the rate of autism patients increased, researchers have tried to find the causes of this disorder. In recent years, there has been great controversy over whether or not thimerosal is a cause of autism.
Thimerosal is the perfect target of research because it is a mercury-based preservative that is used in childhood vaccines. As a result, there have been many experiments studying the relationship between thimerosal and autism. In some studies, there is a causal association between thimerosal and autism. In other studies, there is no difference between thimerosal-contained vaccines, and thimerosal-free vaccines regarding the cause of autism. However, under a critical analysis of these studies, it is more logical to believe that thimerosal does not cause autism.
In three studies conducted by David Geier and Mark Geier, thimerosal had a causal association with autism. In “Neurodevelopmental Disorders after Thimerosal-Containing Vaccines: A Brief Communication,” a study was based upon vaccines administered in the United States, that were linked to thimerosal and neurological disorders. After a statistical analysis of the Vaccine Adverse Events Reporting System database, which is a data collection of the effects of different vaccines, the Geiers found that autism rates were higher in thimerosal-contained vaccines. “We determined based upon our examination of the VAERS database that there were a total of 6575 adverse reaction reports after thimerosal-containing DTaP vaccines and 1516 adverse reaction reports after thimerosal-free DTaP vaccines reported to the VAERS database” (Geier 2002). According to the numbers, there were 5,059 more cases of autism in thimerosal-contained vaccines, than in thimerosal-free vaccines. Another one of their studies found in, “Thimerosal in Childhood Vaccines, Neurodevelopment Disorders, and Heart Disease in the United States,” evaluated the effect of increasing doses of mercury in vaccines on the number of neurodevelopment disorders.
After testing excess amounts of thimerosal, the Geiers discovered a relationship between autism and the amount of mercury in vaccines. We found that the conditions analyzed closely followed linear distributions with an increase of about one case of autism per 100,000 children for every microgram present in childhood vaccines and about one case of speech disorders per 1,000 children for every 3 µg of mercury present in childhood vaccines” (Geier 2003). This means that as the amount of thimerosal increased, the number of autism cases and neurodevelopmental disorders increased as well.
Their most recent study from the journal article, “An assessment of the impact of thimerosal on childhood neurodevelopmental disorders,” combined both an analysis of autism reports from mercury preserved vaccines and previous experiments regarding the effect of thimerosal on autism. This study also yielded similar results to the other studies conducted by David Geier and Mark Geier. It was determined that the odds ratio of autism increased by 0.029 per mg of mercury, personality disorders increased by 0.012 per mg of mercury and mental retardation increased by 0.048 per mg of mercury” (Geier 2003). The more mercury there was in a vaccine, the more likely that a child would have autism or other neurodevelopmental disorders. Based on the results of these three studies, there is statistical and experimental data supporting that thimerosal causes not only autism, but other disorders as well.
In other studies, thimerosal does not have the effect of causing autism. Andrew Hviid, MSc, conducted a cohort study of children born in Denmark, comparing children vaccinated with a thimerosal-containing vaccine with children vaccinated with a thimerosal-free vaccine. In the article, “Association Between Thimerosal-Containing Vaccine and Autism,” Hviid’s analysis revealed that may of the children who developed autism came from both thimerosal-contained vaccinations and thimerosal-free vaccinations. “In those receiving at least 1 dose of whole-cell pertussis vaccine, there were 407 cases of autism (303 receiving thimerosal-free and 104 receiving thimerosal-containing vaccine) and 751 cases of other autisticspectrum disorders (430 receiving thimerosal- free and 321 receiving thimerosal-containing vaccine)” (Hviid 2003). Out of a total of 407 autism patients, more autism patients came from thimerosal-free vaccines, than thimerosal-contained vaccines. In another cohort study, “Thimerosal Exposure in Infants and Developmental Disorders: A Retrospective Cohort Study in the United Kingdom Does Not Support a Causal Association,” Nick Andrews, MSc, investigated the relationship between thimerosal-contained vaccines and neurodevelopmental disorders of children in the United Kingdom. His study found no significant link between thimerosal and autism. “Only in 1 analysis for tics was there some evidence of a higher risk with increasing doses (Cox’s HR: 1.50 per dose at 4 months; 95% confidence interval [CI]: 1.02-2.20)” (Andrews 2004). In general terms of neurodevelopmental disorders, only the numbers of Tourette’s syndrome cases increased as thimerosal levels increased, not autism cases. Based on these two studies, thimerosal has no association with autism rates.
Looking from a critical thinker’s point of view, it makes more sense to believe that thimerosal does not cause autism. First, consider the area of credibility. In the three articles which supported a causal association between thimerosal and autism, written by David Geier and Mark Geier, there is no reference to the education level or occupation of the authors. This makes it highly possible that David Geier and Mark Geier have no experience in research, and have no education in medicine and neurological disorders. However, the studies supporting no association between thimerosal and autism were conducted by people in their specialized fields. Andrew Hviid and Nick Andrews both have a Master’s of Science, which makes them more credible than David Geier and Mark Geier. Second, consider the area of replicability. Only David Geier and Mark Geier’s studies produced results that favored autism being caused by thimerosal. It’s possible that there may be some error in their experimentation and analysis that led them to the wrong conclusion. In the studies conducted by Andrew Hviid and Nick Andrews, the results gathered, debunked thimerosal as a cause of autism in two separate experiments done by two different research teams. Third, consider the area of honesty. The three studies favoring thimerosal as a cause of autism were all conducted by David Geier and Mark Geier. It’s possible that there could have been some bias between the two, because all three experiments produced the same results. On the other hand, there is less room for bias in Hvidd’s case and Andrew’s case, because their studies were conducted separately and produced similar results. Based on an evaluation of credibility, replicability, and honesty, it is more logical to reject the first claim and accept that thimerosal does not cause autism.
