Is Autism a Genetic Disorder

Is autism a genetic disorder? A great deal of research has been done on that question, and the answer, as with most things related to autism, is a resounding...maybe. While that may not be the definitive answer we would like, the fact is that research has not formed a solid conclusion on any one cause of autism. However, much of today's information does lead experts to the conclusion that many autism spectrum disorders do have a strong genetic basis.

Is Autism a Genetic Disorder: Knowns and Unknowns

Roughly 10 percent of cases of autism spectrum disorder can be directly associated with genetic causes, such as Fragile X Syndrome, Phenylketonuria, and Tuberous Sclerosis. As to the other 90 percent of cases, answers are elusive. However, it is a known fact that autism runs in families. Siblings of people with autism are at a substantially higher risk of developing the disorder, and twins often share autistic traits. While this information shows a high probability of a genetic component in autism, there has yet to be a specific gene or group of them definitively identified as an autism cause. Further complicating the question is the vast range of symptoms, which leads many researchers to believe that the various forms of autism may each have a unique genetic basis. At this point, the prevailing theory among autism experts is that a combination of genetic factors and environmental ones may be at the root of the current autism epidemic.

A Sampling of Studies

A study published in July, 2007 lends a new twist to the autism and genetics question. According to the authors of this study, they have discovered a previously unrecognized pattern by examining data on autism incidence. They conclude that the pattern can be explained by assuming that spontaneous germ-line mutations are a significant cause of autism. The study states that women who acquire this mutation do not show symptoms of autism, but have a 50 percent chance of passing that mutation along to their offspring, and sons are often most severely affected. Since the risk of acquiring germ-line mutations rises with age, the study concludes that older parents may be at higher risk for having a child who will develop autism. Further, according to the study authors, female children who have inherited this genetic mutation from their mothers may carry it on to their children, creating high risk families.

Another interesting study on the genetics of autism involved spontaneous mutations in the sperm cells of a man who did not have autism, but passed the mutation along to his two daughters, both of whom developed autism. Examining this case has given scientists more knowledge about how this mutation affects a specific gene, neurexin 1, which was the cause of autism in the two daughters of this particular family. This, as in the study mentioned above, found that a spontaneous germ-line mutation was at fault, present in neither parent, but passed to the offspring. In this case, the mutation occurred only in the father's sperm cells during his own gestation, producing a chromosome that was missing a small piece of DNA. This flawed chromosome, when passed to the daughters, made it impossible for certain proteins to form that are vital to normal development.

Yet another study focused on fathers of autistic children used Israeli draft board records to determine the incidence of autism in children produced by fathers of differing age groups. According to the study authors, children of fathers over 40 show a significant increase in the risk of autism.

These are just a few examples of the thousands of studies done on the basic question, is autism a genetic disorder. Over the past decade, an increasing emphasis has been placed on the issue of spontaneous gene mutations, which are believed to be at the root of sporadic autism. Sporadic autism, defined as cases where there is no family history of autism, account for approximately 90 percent of autism cases. While it is known that various random mutations occur, there are no answers as to why they happen, although environmental insult or advanced parental age are among the theories being investigated. While a number of studies have identified certain genes or “hot spots” in certain chromosomes, results of these studies have been inconsistent. However, each one adds a bit more to the knowledge base, bringing scientists one step closer to finding the genetics at work in autism.

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