The Autism Spectrum

A cognitive neuroscientist explores autism, Asperger's syndrome, and related disorders.

Lindsay M. Oberman, Ph.D. is a cognitive neuroscientist studying autism spectrum disorders. See full bio

Do Mercury or Vaccines Cause Autism?

You can find evidence supporting any theory.

Published on May 13, 2008

Very hot and very controversial topic in the autism literature is whether mercury or vaccines or mercury in vaccines cause autism. In my opinion, No. Now a different question is whether mercury or vaccines are harmful to certain children either in utero or later in development. To this, my answer is maybe. Let's first look at the statements commonly used to support the belief that vaccines cause autism.

1. My child seemed ok, then shortly after he/she received a number of vaccinations (age 1.5-2 years old) he began showing the behavioral signs of autism.
2. There have been studies linking vaccines to autism.
3. Jenny McCarthy said that her son was "vaccine injured"
4. A case was won in Federal Court to a family whose daughter developed autism after receiving vaccines.

Ok, now I will try to discuss each point in turn.

1. To my knowledge there is not any study that has been conducted in a way that would be able to conclude that autism is CAUSED by vaccines. So, what is the difference between saying vaccines caused autism and there is a relationship between vaccines and autism. It is not just semantics! Most of the studies that have been done, including a recent study entitled "Proximity to point sources of environmental mercury release as a predictor of autism prevalence" (which by the way did not look at vaccines, but rather mercury in the air) are what are called correllational studies. Meaning as one factor goes up the other goes up. But this does not mean that the first factor causes the second. My favorite example of this is the relationship between foot size and vocabulary. In childhood as food size increases so does vocabulary. This does not mean that the increasing foot size has anything to do with vocabulary, just that they both increase at the same rate. There are many examples of this. So just because the two things occur at the same time, does not mean that one caused the other. There have been several studies over the years finding contradictory findings. The truth is if your goal is to find studies that support the vaccine theory...you will. If your goal is to find studies that reject the vaccine theory, you will. All studies have flaws and if you are provaccine, you will find flaws with the antivaccine studies and vice versa. Please see http://www.sciencebasedmedicine.org/?p=111 for a critical review of the above study. In my opinion, vaccines do not cause autism. We find differences in brain development in children at risk for autism well before their 2nd birthday when the behavioral symptoms begin to appear and when the vaccines are thought to be "causing" the symptoms. However, could vaccines (or something in the vaccines) cause harm to a developing brain, maybe in some cases. Please note, this is only my opinion, there is no conclusive data on this. But we also need to consider the benefit of vaccination and the prevention of other deadly diseases. In that vein, PLEASE vaccinate your children. But you can ask the doctor to spread out the vaccinations over time so that the baby's little body does not get bombarded with multiple things for their immune system to process at the same time. Many pediatricians will accommodate.

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2. Please see above.

3. Unfortunately Jenny McCarthy, and other celebrities are able to more easily get on TV and to get their message to the general public. I on the other hand have yet to be invited to be on Oprah. This is a problem for scientists. We tend to publish our studies in journals that are not accessible to the public and present new data at conferences that are only open to those with membership to specific scientific societies. On the other hand, celebrities have much more of a platform to promote their beliefs to the general public. This does not, however, mean that their beliefs are any more justified than the scientists. For the reasons stated above, amongst others, the scientific method is used by researchers to try to objectively find causal relationships between factors. So I am sorry to let Jenny McCarthy know that despite her own beliefs (and statements on Larry King Live) "parents' anecdotal information IS NOT science-based information."

4. This is a very specific case in which the child was not healthy prior to the vaccines. What the documents of the case actually read are "In sum, DVIC has concluded that the facts of this case meet the statutory criteria for demonstrating that the vaccinations CHILD received on July 19, 2000, significantly aggravated an underlying mitochondrial disorder, which predisposed her to deficits in cellular energy metabolism, and manifested as a regressive encephalopathy with features of autism spectrum disorder." Thus, this would not apply to most children with autism who do not have this underlying mitochondrial disorder. Also, the fact that a legal case found that there was statutory evidence for compensation, is again, not scientific evidence for a connection.

The take home message here, is that we DO NOT KNOW what causes autism. And if you believe it is bad parenting, you will find evidence for that theory, if you believe it is genetics, you will find evidence for that theory and finally if you believe it is vaccines you too will find evidence for that theory. But please take this "evidence" with very critical eyes. I am very open to hearing your opinions!