What are etiological factors in autism spectrum disorder?

Genetic factors are proposed to play a dominant role in the etiology of autism spectrum disorders. This comes from several lines of evidence: there is a relatively high presence of autism among the siblings of an individual with autism; there are autism features in other disorders wherein genetics are strongly implicated e.g., Fragile X syndrome. For some time, there has been a suggestion that the MMR vaccine heightens risk of autism. Despite the fact that the research that led to this suggestion has been discredited, there continues to be concern about the role of vaccines in autism, to the extent that some parents are refusing to have their children vaccinated. There currently is no evidence for vaccines as a cause of autism.