Psychology Today Blogs - The Autism Spectrum

Do Mercury or Vaccines cause Autism?

Lindsay M. Oberman, Ph.D. — Tue, 13 May 2008 11:36:12 -0700

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.
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!

Has the prevalence of ASD actually increased over the past several years, or are we just better at diagnosing it?

Lindsay M. Oberman, Ph.D. — Sun, 04 May 2008 17:20:26 -0700

After telling people that I am a researcher studying autism, I am often asked the above question. Unfortunately, there is no straight answer for this question. If one goes back in the literature, it is true that for decades (several studies conducted from 1966-late 1990's) the prevalence estimates were on the order of 4-5:10,000 while studies conducted over the past decade have estimated the prevalence on the order of 2-6:1,000 with one study showing as high as 12:1,000. So, why this difference? Is it a real increase in the prevalence of the disorder or something else?

My opinion, and I stress this is only an opinion is that it is likely a combination of several factors in no specific order.

1. We are certainly more aware of the specific deficits defining ASD now as compared to 10 or 20 years ago. Children who previously may have been given a general "Mental Retardation" diagnosis (on the lower end of the spectrum) or just considered socially awkward and not given a diagnosis are now recognized and being correctly diagnosed as having autism and Asperger's Syndrome.
2. The diagnostic criteria for Autism and Autism Spectrum Disorders have changed over the years with Asperger's Disorder only being included in the DSM in 1994.
3. There is now less of a stigma to being diagnosed with autism. In fact if the child has a diagnosis, they are likely to receive extra services from the state including educational services and therapy. Given this change in the stigmatization and opportunity for benefits, parents are perhaps more likely to actively request a diagnosis.
4. Children growing up now are exposed to many more environmental stimulation than children in the previous decades. The influence of the environment on neural development is clear and changes in the environment are much more likely to cause changes in prevalence than changes in genetic mutation over the course of several years.
5. ...?

So, the answer is, yes there seems to be an increase in prevalence over the past several years. But the cause of this apparent increase is still unclear. Whatever the cause, if approximately 24,000 children (just in the U.S. alone) are being diagnosed with a disorder, this is clearly a major public health concern that needs to be studied in an effort to understand the disorder, establish the necessary services for both the children and adults with ASD, and hopefully curtail the current epidemic.

Let Me Introduce Myself

Lindsay M. Oberman, Ph.D. — Tue, 22 Apr 2008 17:53:36 -0700

I first want to introduce myself. My name is Dr. Lindsay Oberman. I am a researcher in Boston Massachusetts and am currently working at Beth Israel Deaconess Medical Center of Harvard Medical School. My research over the past several years has focused on the brain basis of autism spectrum disorders. If you are interested in reading about some of my research I invite you to visit my website where I have posted some of my recent papers that are available for downloading. My website is tmslab.org/faculty/loberman. I can also be reached by e-mail at loberman@bidmc.harvard.edu.

Now a few small caveats. 1. I will be posting topics for the blog that are intentionally somewhat controversial. My opinions on these topics are just that, and should be taken as such. 2. The most truthful answer to most of the topics I will post is "We don't know" but I will try to share some of the research that I am aware of that speaks to the topic. 3. Often times I will speak of autism spectrum disorders, or ASD. Though I acknowledge that autism is qualitatively different than Asperger's Syndrome (a topic that I look forward to discussing in the future) for the purposes of certain topics, I will be speaking of them as a spectrum of one disorder. 4. I am neither a clinician, nor an expert on every child with autism. I cannot diagnose your child nor recommend the best treatment for any given child or adult with ASD. Each individual's diagnosis and treatment plan should be discussed with a local clinician trained in working with individuals with autism spectrum disorders.

That being said, I invite you to share your thoughts, stories, and questions with the blog and look forward to a lively discussion on topics related to autism spectrum disorders.

Topic 1.

Are Autism Spectrum Disorders really just varying degrees of the same disorder or could Asperger's Disorder be a result of a completely different etiology than autism?

Autism Spectrum Disorders are currently categorized under the Diagnostic and Statistical Manual... as mental disorders. As such they are diagnosed based on behavioral symptoms. Though it is appreciated that atypical behavior (and for that matter behavior in general) is a result of activity in the brain (no one will claim that autism is a result of a problem in your big toe!) the exact neurological origin of autism is not currently known. There are certainly more theories out there than one can count, but the data is extremely messy and there are very few markers that all or even most individuals with ASD show.

Why is this? Well, let me give an analogy. Imagine instead of ASD we are talking about a fictitious disorder that I will call "Can't Walk Disorder." Imagine your child is around 12-18 months and you notice that most of his playmates are beginning to walk, but your child does not. You bring the child to the doctor and he asks you a list of questions "Can he walk if his weight is supported?" "Can he move his legs in any way" "Can he crawl?" You answer "No" to all the questions and the doctor says "Well, your child meets the criteria for ‘Can't Walk Disorder.' The current treatment for this is crutches. They will help your child function better in the world and compensate for his deficits." Though this treatment is better than nothing, it treats the symptoms, not the fundamental biological basis of the problem. It is possible in this example that the child broke his legs, or perhaps he is paralyzed, or perhaps he has a muscular problem.

Research into the brain basis of autism spectrum disorders is thus somewhat of a circular problem. We define our inclusion criteria for our study based on a behavioral diagnosis of ASD and try to find a biological marker that all or most participants share. However, if there is not a singular etiology that leads to the behavioral disorder, then looking for a singular marker may be fruitless if in fact we have a heterogeneous group. So, why even try? Well, I believe that crutches aren't good enough. I feel that in order to effectively treat (and perhaps some day cure) autism spectrum disorders, then one needs to identify the underlying cause.

So, what do I think? I have known many children and adults with autism and Asperger's Syndrome and though each is unique, I find not simply quantitative, but rather qualitative differences in their behaviors. For example while some individuals with autism do not interact socially, while individuals with Asperger's Syndrome tend to make social overtures, but these overtures are often scripted, inappropriate or narcissistic in nature (relating to the individual's specific interests). As with many of the topics I will discuss in this blog, the truth is we don't know, but if I had to make a guess, I would predict that the underlying cause of ASD will be as complex as the disorder itself.