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What Causes Autism Spectrum Disorders?

Updates on the latest research

What Causes Autism Spectrum Disorders?

In response to the question, "What causes autism spectrum disorders (ASDs)?" the writer is sorely tempted to reply, "We don't know," and move on to the next chapter. However, no guide to ASDs would be complete without an attempt at explaining the causes of the most recent epidemic to hit our planet.

What Does Not Cause ASDs? It is infinitely easier to talk about what we know does not cause ASDs. It is known for a fact that ASDs cannot be caught through osmosis, dirty doorknobs, or bad parenting. Other than that, nothing can be said for sure.

Where to Get Updates on the Latest Research

What follows is by no means an exhaustive look at the science behind the causes of autism. The interested reader can follow on a regular basis the latest discoveries and ongoing research. It is best to read the actual study or report than to read summaries and news releases. In order to gain an understanding of this highly controversial topic, the reader is advised to consult a wide variety of websites and journals such as those listed below and form his own opinion:

• The National Library of Medicine Pubmed (www.ncbi.nih.gov/entrez/query.fcgi): Use the search engine to find abstracts of any research articles you are interested in reading concerning autism. There are tutorials on the site with instructions for more advanced search techniques. Some abstracts will link you to the full article on the website of the journal where it is published. Some journals will provide full text for free, while others require a subscription or fee.
• The Medical Research Council (UK) (www.mrc.ac.uk): Information on current research funded by the MRC is listed on its website. The MRC published the "MRC Review of Autism Research: Epidemiology and Causes" in December 2001.
• The Schafer Autism Report is the largest daily (almost) newspaper on ASDs; edited by Lenny Schafer and available free through the Internet. To subscribe: http://www.sarnet.org. For archives: http://groups.yahoo.com/group/AuTeach/messages.
• The Autism Research Institute International Newsletter (www.autismresearchinstitute.com): Bernard Rimland, Ph.D., publishes a quarterly newsletter with summaries of current research. The ARI website has information on some research studies.
• The Autism Society of America (ASA) (www.autism-society.org)often has information about the most important ASD issues being discussed by the media.

What causes ASDs?

What Is Known about the Causes of ASDs?

There is much discussion on this issue, and research studies are often published that are sometimes disputed or explained away by other research. However, there is strong evidence for a genetic component and a biological basis. Most researchers believe that ASDs have different causes that may be affecting the same brain systems or hindering development by disrupting the different abilities needed for communicative and social development. Here is what is known and accepted to be true by almost everyone:

• There is a genetic predisposition to autism. Regions of interest, sometimes called "hot spots," have been found on certain chromosomes, the most important so far on chromosome 7q, although others are involved. If one identical twin has autism there is a 60-95 percent chance of the other having it as well. However, identical twins with the same genetic makeup and the same physical environment may have different expressions of ASDs—one may be very able, the other very disabled.
• There have been a number of findings in regard to differences in brain activity, not all in agreement with each other. However, most scientists who study autism would agree that some brain circuits are different in a person with an ASD.
• Serotonin, a neurotransmitter important for normal brain functioning and behavior, has been found elevated in a subgroup of people with autism and in some first-degree relatives who are unaffected. This is the only key biochemical finding since the 1960s that has held up to be true over time.
• There is a large body of anecdotal findings reported by parents and medical professionals that some children with ASDs appear to have biochemical and immunological problems. Some possible causes being mentioned are: mercury toxicity, yeast problems, casein and gluten sensitivity, and viral infections.
• In some studies, different levels of environmental toxins such as lead, antimony (a flame-retardant chemical present in many house-hold items), and aluminum have been found in hair and blood samples of children with autism than in those of nonautistic children. This leads to the hypothesis that some children with ASDs cannot detoxicate, and thus accumulate toxins in their bodies.

For a long time, the favored theory was that autism was all about the genes. It is true that genes come into play. However, the dramatic rise in recent years in ASDs cannot be attributed to a rise in genetic anomalies.

Perhaps we are seeing different disorders, each caused by a different problem but with symptoms resembling one another. Perhaps the differences are all being caused by a yet unknown single underlying cause.

It appears most likely that there is a genetic predisposition to autism spectrum disorders interacting with environmental factors that may play a key role in affecting the gastrointestinal tract, the immune system, the sensory nervous system, and the brain.