Possible
Causes of Autism
It is generally accepted that autism is
caused by abnormalities in brain structures
or functions. The brain of a fetus develops
throughout pregnancy, and, at the time of
birth, has become a complex organ with
distinct regions and subregions, each with a
precise set of functions and
responsibilities.
Brain development does not stop at birth,
however. The brain continues to change
throughout the first years of the child's
life. Scientists are learning that a number
of problems may interfere with the brain's
development. For example, certain types of
cells may migrate to places in the brain
where they are not meant to be. Some parts
of the brain's intricate communication
network may disrupt the overall task of
coordinating sensory information, thoughts,
feelings and actions.
Among the possible factors contributing
to autism is heredity. Several studies
involving twins suggest that autism can be
inherited. This is also supported by
findings that suggest parents who have one
child with autism are at slightly increased
risk for having more than one child with
autism. While genetics does seem to play a
role in autism, it does not seem to be due
to one particular gene. While no one gene
has been identified as causing autism,
researchers are searching for irregular
segments of the genetic code that autistic
children may have inherited. It also appears
that some children are born with a
susceptibility to autism, but researchers
have not yet identified a single "trigger"
that causes autism to develop.
Another potential factor in the
development of autism is the pregnancy
period itself. As the brain grows and
develops during pregnancy, anything that
disrupts normal brain development may have
lifelong effects on the child's sensory,
language, social and mental functioning. For
this reason, certain conditions, such as the
mother's health during pregnancy or problems
involving the delivery, are being researched
to see if they interfere with normal brain
development.
Individuals who have certain medical
conditions seem to be more at risk for
autism. These conditions include Fragile X
syndrome, tuberous sclerosis, congenital
rubella syndrome, and untreated
phenylketonuria (PKU).
An area of controversy and concern in the
autism community is the link between
vaccinations and autism. In particular,
vaccines which contained thimerosal (a
mercury-based preservative) are believed by
some to be associated with the development
of autism.*
Another area of controversy is whether
the Measles-Mumps-Rubella (MMR) vaccine is
linked with autism. In a 2001 investigation
by the Institute of Medicine, an expert
committee concluded that the "evidence
favors rejection of a causal
relationship.... between MMR vaccines and
autistic spectrum disorders (ASD)."
Moreover, a recent Danish study of the
health records of over 530,000 children in
Europe found that the rate of autism was
virtually the same for children who had
received the MMR vaccine and those who had
not. While many researchers note that there
is no definitive proof of a link between the
MMR vaccine and autism, most agree that more
research is needed.
*Thimerosal is no longer used in
vaccines administered to children six months
and
younger in the US.
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