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Is Autism Caused by Genes or the Environment?

There is not a single gene that triggers autism, but more likely dozens of genes that enhance the risk of autism. On the other hand, researchers have found that certain environmental variables, like air pollution, may also play a small role. 

The root cause of autism may lie in genes that affect the brain’s “hardware,” rendering it too inflexible to adapt its connection patterns to a variety of key functions. That’s what Dr. Christopher Walsh of the Children’s Hospital of Boston tells Big Think in Part 2 of our Breakthroughs: Autism series. In the normally functioning brain, Walsh explains, fibers and cells develop “different software apps for language or apps for social behavior.” In the autistic brain, meanwhile, “it’s these patterns of changes in connections that don’t seem to work.” As a result, current genetic research into autism has zeroed in on those genes that regulate patterns of connectivity between neurons.

As Dr. Gerald Fischbach of the Simons Foundation cautions, however, the likelihood of pinning autism to a single gene is small. “What is much more likely,” he says, “is [that] there may be more than 100 genes that enhance the risk of autism,” complicating the search for prevention and treatment options. At the same time, according to neuroscientist Dr. Susan Bookheimer of UCLA, extensive research into environmental triggers for autism has produced very few leads—though a recent study suggests that heavy air pollution may pose a small additional risk. As for the notion, advanced in the late 1990s by Dr. Andrew Wakefield and popularized by celebrities such as Jenny McCarthy, that childhood MMR vaccines are linked to autism, it has now been almost entirely discredited.

While evidence of a genetic basis for autism is mounting, that is not necessarily bad news for current sufferers. Walsh notes that “although we think that there is a large genetic component to the disease, it’s by no means all genetics, in the sense that the genes that are in play are those regulate the way the brain responds to the environment….We know that there are ways that the brain can be changed by different sorts of teaching, different sorts of environments.” The likelihood—and, for sufferers, hope—is that “genetic predisposition is not immutable, that there might be ways it can be modified or improved.”

For more insight into the current state of autism genetics research, including the search for a “unified theory of autism,” see Big Think’s interview with Dr. Michael Wigler of Cold Spring Harbor Laboratory from May 2010, as well as the Resources list below.

More Resources:

Science News from Autism Speaks. Digest of the latest research on the disorder, including links to scientific papers.

What Really Causes Autism? Seed Magazine article on current autism science (and myths).

Vaccines and Autism Timeline: How the Truth Unfolded. Chart tracking the rise and fall of the now largely discredited notion that vaccines cause autism.

The views expressed here are solely those of the participants, and do not represent the views of Big Think or its sponsors.

Image courtesy of Wikimedia Commons user Genghiskanhg.


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