Researchers from all over the world are devoting considerable time and energy to finding the answer to this critical question. Although a single specific cause of autism is not known, current research links autism to a number of neurological differences. In some families, there seems to be a pattern of autism or related disabilities, and research suggests that there is some genetic basis to the disability. Any genetic basis is believed by researchers to be highly complex, involving numerous genes in combination.

Several outdated theories about the cause of autism have been proven to be false: autism is not a mental illness; children with autism are not simply unruly kids who do not choose to behave; autism is not caused by bad parenting and autism is not caused by vaccinations. Further, no known psychological factors in the development of a child have been shown to cause autism.