Autism Spectrum Disorders are believed to be a biologically based neurodevelopmental disability with a genetic basis. Research scientists recognize that a number of problems may interfere with normal brain development and that problems with the communication network interfere with the overall task of coordinating sensory information, thoughts, feelings and actions. There also is the possibility that environmental triggers (i.e., pollution, chemicals, etc.) alter the usual patterns in genes.
Individuals can share common characteristics on the spectrum, but Autism is unique to each person and will be different for each one. Until we have more definitive answers on the causes of Autism, it seems to make sense to focus more on treatments, early intervention, and to support researchers as they learn more about causes.
Link between heredity, genetics and medical problems - In many families, a pattern of Autism or related disabilities, supporting Autism’s genetic basis, appears to exist. So far, there has not been any single gene that has been identified as causing Autism, so scientists are researching irregular segments of genetic code found in autistic children that they may have inherited. It's possible that many different genes are implicated in Autism -- and that different sets of genes may be implicated for different autistic people, as the disorder presents within a wide spectrum. Some children appear to have been born with a vulnerability to Autism, but researchers haven’t yet identified a single "trigger" causing Autism to develop.
Problems During Pregnancy - Researchers are currently investigating problems during pregnancy or delivery that might have caused a child’s susceptibility to Autism. Some harmful substances (e.g. cocaine) ingested during pregnancy also have been associated with an increased risk of Autism.
Environmental Factors - Viral infections, metabolic imbalances, and exposure to environmental chemicals are being researched as possible causes for Autism.
Vaccines – The relationship between vaccines and Autism continues to be debated. The first theory suggests that the MMR (Mumps-Measles-Rubella) vaccine may cause intestinal problems leading to the development of Autism. The second theory suggests that a mercury-based preservative called thimerosal, used in some vaccines, could be connected to Autism. Though a 2001 investigation by the Institute of Medicine concluded that the "evidence favors rejection of a causal relationship between MMR vaccines and autistic spectrum disorders” the Institute could not rule out the possibility that vaccines may affect a small number of children affected with ASD, so research is continuing.
Atypical Brain Development - Some researchers have found differences between the autistic brain and the typical brain. Autistic individuals seem to have larger brains. They also seem to process information differently; in other words, their brains are "wired" differently.
Immune Deficiency - There is some evidence that Autism is linked to problems in the immune system. Autistic individuals often have other physical issues related to immune deficiency. Some researchers say they have developed effective treatments based on boosting the immune system. The NIH, however, states that the evidence is not yet strong enough to show a causal relationship.
Food Allergies - There is some evidence that allergies to certain foods could contribute to autistic symptoms. Most people who believe in this theory feel that gluten (a wheat product) and cassein (a dairy product) are the most likely causes. Research continues into this hypothesis.
Poor Nutrition – Malnutrition by itself is not likely the cause of Autism. However, megavitamin therapies have been used for many years to treat autistic symptoms. Dr. Bernard Rimland formerly of the Autism Institute, was an advocate for this theory.
Psychological Factors – It is generally now agreed that psychological factors in the development of the child do not cause Autism, including now disregarded theories concerning bad parenting, unruliness (bad behavior), and mental illness. Because it is now agreed on by researchers that children with Autism and PDD are born with the disorder or born with the potential to develop it, psychological factors have been completely ruled out, to the benefit of families that are dealing with an autistic child.
Television Watching – Researcher Michael Waldman, from the Johnson School of Management at Cornell University, has hypothesized that for some children vulnerable to developing Autism due to underlying genetics, extensive early childhood television viewing can serve as an environmental trigger. His study focuses on 3 states, California, Washington, and Oregon that have high rates of Autism along with high rates of cable subscription and high rates of precipitation (meaning more television watching due to bad weather).