Autism myth lives on
Why people continue to blame vaccines, despite evidence to the contrary.

By Sam Wang

As the brother of an autistic person and a brain scientist, I have been
hoping that the increased focus on autism in the news would lead to a
greater public understanding of this disorder. Instead, I am angry that
this coverage is spreading dangerous myths.

My sister, Karen, is autistic. In the 1970s, my parents wondered why she
behaved so differently. At the time, a prevalent idea was that an
emotionally distant mother could somehow prevent a child from
understanding emotions or relating normally to others. Our parents had a
simpler idea, that they might have hurt Karen’s head during a bath.

Both these ideas are wrong. Autism is a neurological disorder, and its
signs appear by the age of 1 or even earlier. It is highly inheritable.
In identical twins where one is autistic, the chance that both are
autistic is greater than 50-50. Even non-identical twins and siblings
are at increased risk. In short, I dodged a genetic bullet. Now I worry
about my daughter.

A link that isn’t there

Recently, celebrities such as Jenny McCarthy and other activists have
taken to the airwaves to repeat the myth that autism is linked to
vaccination. Although peer-reviewed scientific evidence overwhelmingly
opposes their views, they have attracted attention. In a recent
discussion on Larry King Live, three pediatricians invited to make the
case for science were no match for McCarthy’s star power. Situations
like this could mistakenly persuade parents to leave their children
unvaccinated and vulnerable to contagious diseases.

Speculation about a vaccine-autism link began with a 1998 uncontrolled
study of a few autistic children. But the conclusions were later
retracted. Subsequent speculation focused on the compound thimerosal.
But removing it from all routine childhood vaccines in the USA, Denmark,
Sweden and Canada has not decreased autism rates.

What are McCarthy’s credentials? She is an actress and comedienne – with
an autistic son. Her career took on new life after she wrote a
best-selling pregnancy guide. Like all parents of autistic children, she
wrestled with the question of what caused his disorder. She recalled
that her son was vaccinated about the time his symptoms first appeared.
Aha! That’s it. Here is an example of her reasoning: “I believe that
parents’ anecdotal information is science-based information.”

How we’re wired

Although her concept of evidence is flawed, I don’t blame her. The error
highlights how our brains are wired to think. Like the authors of the
1998 study, she concluded that two events happening around the same time
must be linked. They used the principle that coincidence implies a
causal link. But there was no coincidence for her son: He was born in
2002, after thimerosal was removed from vaccines.

The problem is compounded by “source amnesia,” in which people are prone
to remember a statement without recalling where they heard it or whether
the source was reliable. Presidential candidate John McCain might have
fallen prey to source amnesia when he repeated the vaccine-autism myth
last month. Recollection is more likely when the “fact” fits previously
held views; parents might already dislike vaccinations based on their
kids’ reaction to shots. But when it comes to a complex issue such as
autism, such errors of reasoning hinder us from distinguishing real
causes from coincidences.

Out of sight of the cameras, increased research funding is spurring
efforts to find autism’s causes. Scientists are vitally interested in
possible environmental influences. But the vaccine story is a dry well.
Working on it further wastes valuable time and resources. It’s time to
dig elsewhere.

As I watch my beautiful 10-month-old daughter grow, I wish that
preventing autism were as simple as withholding a few injections. But
along with my wife, a physician, I understand the vital importance of
vaccination, not only for maintaining our baby’s health but also
protecting our community from infectious diseases. Our daughter’s next
shots are in two months.

Sam Wang is an associate professor of molecular biology and neuroscience
at Princeton University. He is a co-author of Welcome to Your Brain: Why
You Lose Your Car Keys But Never Forget How to Drive and Other Puzzles
of Everyday Life.

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