By: Erin Thomas

The question on everyone’s minds…

With an astounding incidence of autism in the U.S. today
that only seems to be growing, it is even more astounding that a definite cause
has yet to be found.  Autism has done a
successful job of leaping into the public eye and vernacular; fifteen years ago, talk about having an autistic child likely would have
been met with confused gazes. It is understandable that the lack of an explicit
cause is a frustrating reality for so many individuals on the Autism Spectrum and
their families. Without a cause, it becomes all the more difficult to target a treatment
for an individual, and families are often left shooting in the dark for
therapies.

One school of thought that has pervaded the media is the
connection between the Measles-Mumps-Rubella (MMR) vaccine and autism. You may
have heard public figures, most notably Jenny McCarthy, promoting the
culpability of MMR as a cause of autism. Well, from a scientific standpoint,
you may be surprised to hear that there has been NO scientific evidence to
support this claim. Not one. So how did this idea gain fuel and become so embedded in the public perception of autism?

Quick history break- Well in 1998, a gastroenterologist
named Andrew Wakefield published a paper in Britain describing 8 children who apparently
experienced the onset of autism one month after receiving the MMR vaccine.
Wakefield claimed that the MMR vaccine caused intestinal inflammation that
allowed certain peptides (chains of two or more amino acids, similar to proteins
but normally smaller) to enter the bloodstream and thus make their way to the
brain where they affected development (Gerber, Offit, 2009). Wakefield was
eventually prompted to take down his paper because of the

•  lack of experimental controls to confirm that
  MMR was responsible for causing the autism
• the unsystematic method in which data was
  collected
•  the lack of connection between measles, mumps,
  or rubella to intestinal inflammation, and
• the fact that gastrointestinal issues did not
  even precede autism onset in some children. (Click here to read more about the issues nullifying the Wakefield paper.)

Since then, research has been conducted to further rule out
MMR’s role in causing autism. For one, research has not determined that children
with ASDs contain more of the genetic information of the measles vaccine virus than
those without ASDs (Hornig, 2008). Moreover, the harmful peptides Wakefield suspected
to have been invading the brain from the intestine have not been identified
(Gerber, Offit, 2009). In fact, the proteins now believed to contribute to ASDs
are endogenous, or have no external origins, and affect neuron activity
(Sutcliffe, 2008). 

Studies have further severed the link between the MMR
vaccine and autism by showing that the incidence of autism has not increased
since people started becoming vaccinated against MMR.  An extensive study on 498 autistic children
born from 1979-1992 in the UK is just one source of evidence that rates of
autism did not increase after the introduction of the MMR vaccine in 1987. Nor
did children who received the MMR vaccine or a second dose of the vaccine have higher onsets of
autism than unvaccinated children (Farrington, 2001). Click here for an outline
of more studies that have refuted the connection between MMR and autism. 

So if there is no
scientific evidence supporting the link between the MMR vaccine and autism,
and no logical scientific mechanism for how
MMR could even lead to autism, why is the idea still lingering in the minds of
parents taking their newborns to the pediatrician’s office?   

The MMR vaccine is administered in babies at 18 months…right
around the time when autism is typically first detected (although in some cases
it can now be detected earlier). Scientists have coined the term “correlation
vs. causation” to illustrate an important fallacy associated with the connection being made here. For example, if I notice that the number of sick people in the
U.S. increases as the consumption of hot chocolate in the country increases, is
it safe to say that drinking a sweet cup of Swiss Miss causes people to fall
ill? Of course not! The two are simply correlated because people happen to consume
more hot chocolate in the winter, which is when flu season is at its peak. Similarly,
the correlation between the administration of MMR vaccines at 18 months and the
subsequent diagnoses of autism around that time does not necessarily link the
vaccine to the cause of autism. This correlation vs. causation issue is
something we will keep in mind as we continue to assess ongoing autism
research. 

Farrington
CP, Miller E, Taylor B. MMR and autism: further evidence against a causal
association. Vaccine. 2001;19:3632–5. [PubMed]

Gerber J, Offitt P. Vaccines and
autism: a tale of shifting hypotheses. Clinical Infectious Diseases. 2009;48:456–461 [PubMed]

Hornig M,
Briese T, Buie T, et al. Lack of association between measles virus vaccine and
autism with enteropathy: a case-control study. PLoS
ONE. 2008;3:e3140.

Sutcliffe
JS. Genetics: insights into the pathogenesis of autism. Science.
2008;321:208–9. [PubMed]