Although it's been three hundred years since the first properly documented
case of autism in 1747, we still do not have a definitive answer to what causes
the five autism spectrum disorders – Rett Syndrome, Asperger Syndrome, Childhood
Disintegrative Disorder (CDD), PDD-NOS (Pervasive Developmental Disorder – Not
Otherwise Specified) and Kanner's Autism.

Researcher, parents and doctors are still debating whether autism is caused
by genetics, environmental factors or other causes. Here are just some of the
theories that people put forward as to the cause of autism spectrum

  • Vaccines – The vaccine debate was started in 1998 when research by London's
    Royal Free Hospital was published in the British medical journal, “The
    Lancet”. This research suggested that some children had developed
    developmental disorders and gastrointestinal problems (both symptoms of
    autism) after being vaccinated with the MMR vaccine. In the US, autism
    crusader Jenny McCarthy has drawn people's attention to the fact that autism
    rates have risen along with an increase in the number of vaccines given to
    babies and young children. Some people also believe that it's not the live
    vaccines themselves, but the fact that vaccines used to contain a mercury
    based preservative, thimerosal, that is the problem. Thimerosal has been
    removed from children's vaccines but may still be found in vaccines given to
    pregnant women and some medicines.

  • Birth Injury – Some researchers, like Harch and McCullough (“The Oxygen
    Revolution”) are of the opinion that many autistic children have suffered
    trauma to the brain during birth.

  • Mitochondrial Dysfunction – Some studies, including one carried out in
    Portugal, have suggested that there is a link between mitochondrial disease or
    dysfunction and autism because mitochondrial dysfunction is more common in
    people with autism.

  • Gut Problems – Many studies have suggested that there is a
    gut-brain link with autism and that autism is caused by an inability to
    metabolize certain foods, problems with digestion or an imbalance of flora in
    the gut. According to research carried out by Valicenti-McDermot et al.,
    around 70% of children with autism also have gastrointestinal problems.

  • Heavy metals – Many people believe that autism can be caused or
    triggered by exposure to heavy metals in the environment. Heavy metals like
    cadmium, manganese, lead and mercury are found in the air we breathe, the food
    we eat, the water we drink and things around us. Usually the human body can
    deal with these heavy metals, excreting them, but studies have suggested that
    some children are unable to do this and the heavy metals build up, causing

  • Genes – Some scientists believe that genes have a role to play
    in autism, either directly causing autism or by leaving a child susceptible to
    having autism triggered by environmental factors.

  • Environmental causes – As well as vaccines and heavy metals, our
    children are also exposed to toxins like pesticides, PCBs and dioxins,
    emissions and solvents. These toxins are known as neurotoxicants because they
    can damage the brain and impair a child's development. child could then go on
    to develop autism if there is a trigger like an environmental factor or

  • Candida Yeast – An overgrowth of candida yeast in the gut can
    produce toxins which are then carried around the body and can adversely affect
    a child's immune system and brain. Studies have shown that autistic children
    often have too much candida yeast in their guts.

  • Food intolerances – Foods like gluten and casein are well known
    “allergic foods” which some studies have linked to symptoms of autism. Diets
    like the GFCF Diet, SCD and Feingold Diet have been affective with many
    autistic children.

  • A Mother's Antibodies – Research by John Hopkins Children's
    Center concluded that a pregnant woman's immune system can actually produce
    antibodies against her baby's brain tissue which then cross the placenta,
    enter the baby's bloodstream and attack it's brain.

  • Nutritional deficiencies – Some research has found that autistic
    children are deficient in key nutrients such as vitamin A, D and B group
    vitamins, minerals like zinc, calcium and magnesium, and omega 3 essential
    fatty acid. These deficiencies can be corrected by a healthy diet and

Research is still going on in each of these areas and it may be
that autism is actually caused or triggered by a combination of

Author's Bio: 

Dr Chun Wong is a practicing physician in Illinois and specializes in the biomedical approach to Autism. He spends his time researching the treatment of Autism in children.

You can get more information about Dr Chun Wong and Autism from