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Although it is generally accepted that autism has neurobiologic causes, the precise nature of those causes is as yet unknown. There is an increased incidence of autism with certain disorders, such as fragile X
syndrome, tuberous sclerosis, encephalitis, or untreated PKU.
Autism may co-exist with other syndromes or symptoms, such as severe impairments of vision or hearing. Researchers are investigating a number of theories, including the roles of heredity, genetics, and medical
problems. Some families appear to demonstrate a pattern of autism or related disabilities, further supporting the theory of a genetic basis for the disorder in these cases. The present state of research
hypothesizes that autism is not caused by a single gene, but more likely by a combination of several contributing genes. Several researchers have proposed a relationship between vaccines, particularly the measles,
mumps, rubella (MMR) vaccine, and autism. Research is continuing to address these issues.
What we do know is that autism spectrum disorders are not caused by bad parenting. No known psychological factors in the development of the child have been shown to cause autism.
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