Autism is a result by a general chemical imbalance. The causes to this imbalance are many, but two are generally debriefed below.
Genetics. Autism's are tangled and many undiscovered; "Autism is not a disease, but a syndrome with multiple nongenetic and genetic factors." (2) The most compelling point [is] genetic susceptibility." For example, he explains, "there's a 3 to 8 chance of having a second child with autism, and a 30% greater likelihood that identical twins will be autistic than fraternal twins." Additionally, "autism is four to five times more common in males than females." (3)
Aside from probability, inheritance also may also increase autism's expression. By 2012, much research has been done to confirm that genetics does indeed play its role in autism's manifestation. However, also by 2012, the rate of autism's diagnoses (needs to be specified as thus), has experienced an exponential increase which cannot only be held accountable by genetics. Genes do not change that fast.
Environmental Factors. To also account for the exponential increase, scientists have pinpointed some environmental conditions which could lead to autism's development.
To name a few:
- viruses (3)
- mercury preservative (3)
- Thimerosal (3)
- mumps-measles-rubella (MMR) childhood vaccine (3)
- pregant mothers' exposure to toxic pollutants (3)
- household products (2) -- chemicals and cleaning products
- polychlorinated biphenyls (2)
- lead (2)
- brominated flame retardants (2)
- pesticides (2)
Sources:
1. The Genetics of Autism (http://www.ncbi.nlm.nih.gov/pubmed/15121991)
2. New Study: Autism Linked to the Environment (http://www.scientificamerican.com/article.cfm?id=autism-rise-driven-by-environment)
3. The Autism Answerbook by William Stillman
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