Causes

There are probably a variety of factors leading to autism, but no conclusive link has been established.
Some data indicate that individuals with autism have a chemical imbalance in the brain, particularly in higher levels of serotonin. However, it was not clear whether a relationship exists between the two that would explain the presence of autism.

Heredity is a factor in a small percentage of autism. In studies of identical twins where one twin has autism, the chances that the other should also be about 85%. The probability of autism among siblings of an autistic person is above the frequency observed in the general population.