Folk epidemiology of autism refers to the popular beliefs about the origin of autism. Without direct informed knowledge of autism, a complex disorder, members of the public are influenced by rumors and misinformation presented in the mass media and repeated on social media and the internet. These misinformed beliefs persist even when contradicted by scientific evidence. Folk epidemiology persists because people seek, receive, and preferentially believe information that is consistent with their existing views; misjudge the reliability of their sources of information, and are misled by anecdotal evidence; and tend not to revise their opinions even when their original sources of information are shown to be wrong.