instruction: What are the causes of Autism?
context: Many causes of autism have been proposed, but understanding of the theory of causation of autism, or otherwise known as autism spectrum disorder (ASD) is incomplete. Attempts have been made to incorporate the known genetic and environmental causes into a comprehensive causative framework.ASD is a complex developmental condition marked by persistent challenges to social interaction, speech and nonverbal communication, and restricted/repetitive behaviors and its phenotypes vary significantly.
  
  
  Research indicates that genetic factors predominate. The heritability of autism, however, is complex, and it is typically unclear which genes are involved.In rare cases, autism is associated with agents that cause birth defects.Many other causes have been proposed.
  Numerous epidemiological studies have shown no scientific evidence supporting the controversial but popular theory that autism is caused by vaccines.
response: There is no clear cause for Autism which has been scientifically proven. However, some research indicates that genetic factors are one of the predominant causes. In rare cases, autism is associated with agents that cause congenital disabilities, and many other causes have been proposed.
  Numerous epidemiological studies have shown no scientific evidence supporting the controversial but popular theory that vaccines cause autism.