What Causes Autism?
There is no known single cause for autism, but it is generally
accepted that it is caused by abnormalities in brain structure or
function. Brain scans show differences in the shape and structure of
the brain in children with autism versus neuro-typical children.
Researchers are investigating a number of theories, including the
link between heredity, genetics and medical problems. In many
families, there appears to be a pattern of autism or related
disabilities, further supporting a genetic basis to the disorder.
While no one gene has been identified as causing autism, researchers
are searching for irregular segments of genetic code that children
with autism 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.
Other researchers are investigating the possibility that under
certain conditions, a cluster of unstable genes may interfere with
brain development, resulting in autism. Still other researchers are
investigating problems during pregnancy or delivery as well as
environmental factors, such as viral infections, metabolic
imbalances, and exposure to environmental chemicals.
Genetic Vulnerability
Autism tends to occur more frequently than expected among
individuals who have certain medical conditions, including Fragile X
syndrome, tuberous sclerosis, congenital rubella syndrome, and
untreated phenylketonuria (PKU). Some harmful substances ingested
during pregnancy also have been associated with an increased risk of
autism. Read more about related conditions.
Environmental Factors
Research indicates that other factors besides the genetic component
are contributing to the rise in increasing occurrences of ASD, such
as environmental toxins (e.g., heavy metals such as mercury), which
are more prevalent in our current environment than in the past.
Those with ASD (or those who are at risk) may be especially
vulnerable, as their ability to metabolize and detoxify these
exposures can be compromised.