Genetic and Environmental Causes
Autism causes are a complex mix of genetic and environmental factors that researchers have yet to fully understand. Studies of identical and fraternal twins reveal that genetics play an important role in autism.
A Brief Description of Autism
Defining autism is difficult, as the disorder covers a wide range of symptoms and severity can range from mild to debilitating. A neurological disorder, it causes impairment in social interaction and communication. A person with autism may have restricted interests or engage in abnormal, repetitive behavior. Depending on the severity of symptoms, it causes mild to debilitating impairment.
Autism is part of a group of related disorders collectively called autism spectrum disorders (ASDs). The autism spectrum, as its name implies, describes a range of symptoms, rather than specific disorders. Other ASDs include Asperger’s syndrome, Retts syndrome and childhood disintegrative disorder, as well as pervasive developmental disorder, not otherwise specified.
Genetic Autism Causes
Most cases have no known cause, but the tendency for disorders of the autism spectrum to run in families suggests a genetic component. Families with one autistic child have a 3 to 8 percent chance that their other children will be autistic.
Twin studies demonstrate the importance of genetics in establishing causes. If one identical twin has autism, studies reveal a 30 percent chance that the other twin is also autistic.
In addition to twin studies, autism research reveals that families of autistic children have a much higher rate of communication defects, impaired social skills or restricted interests, all of which are hallmarks of classic autism and fall within the autism spectrum.
Despite the strong evidence for genetic causes, parents of autistic children are rarely autistic themselves, although they may display personality traits suggestive of autism. Genetics alone, then, does not necessarily account for autism.
Environmental Catalysts and Autism Genetics
Many researchers believe that the potential for autism lies in genetics, but environmental factors are required to “trigger” the disease. Over time, a number of environmental causes have been identified that may act as catalysts for autism, including:
- bacterial meningitis
- cytomegalovirus
- developmental brain disorders
- fragile X syndrome
- lead encephalopathy
- rubella
- some metabolic disorders
- toxoplasmosis
- tuberous sclerosis.
These disorders are not considered definitive causes. Most children who experience these conditions do not develop autism. However these conditions may interact with existing genetic factors, resulting in autism.
Vaccination and Disproven Autism Causes
Some suggested causes have proven false. The early theory that a distant or uncaring mother causes autism has long been disproven.
More recently, an argument was made that the mercury preservative used in vaccinations caused autism. Despite significant research, no link between vaccination and autism has ever been found.
Genetics, Autism and the Future
Most researchers doubt that causes can be traced to a single gene. Instead, they believe that a number of different genes contribute to the development of autism. Some autism experts have even speculated that in the future, what we now label autism will be recognized as a group of similar, but separate diseases.
It may take years to unravel the roles genetics and environment play in autism, but the goal is attainable. Understanding autism causes will help the search for effective treatments and better therapies for autism.