Cause of Autism and Does Inheritance play a role?

What causes autism?

Scientists aren’t certain about what causes ASD, but it’s likely that both genetics and environment play a role.  Researchers have identified a number of genes associated with the disorder.  Studies of people with ASD have found irregularities in several regions of the brain.  Other studies suggest that people with ASD have abnormal levels of serotonin or other neurotransmitters in the brain.  These abnormalities suggest that ASD could result from the disruption of normal brain development early in fetal development caused by defects in genes that control brain growth and that regulate how brain cells communicate with each other, possibly due to the influence of environmental factors on gene function.  While these findings are intriguing, they are preliminary and require further study.  The theory that parental practices are responsible for ASD has long been disproved.

What role does inheritance play?

Twin and family studies strongly suggest that some people have a genetic predisposition to autism.  Identical twin studies show that if one twin is affected, there is up to a 90 percent chance the other twin will be affected.  There are a number of studies in progress to determine the specific genetic factors associated with the development of ASD.  In families with one child with ASD, the risk of having a second child with the disorder is approximately 5 percent, or one in 20.  This is greater than the risk for the general population.  Researchers are looking for clues about which genes contribute to this increased susceptibility.  In some cases, parents and other relatives of a child with ASD show mild impairments in social and communicative skills or engage in repetitive behaviors.  Evidence also suggests that some emotional disorders, such as bipolar disorder, occur more frequently than average in the families of people with ASD.