Autism is a brain development disorder characterized by impaired social interaction and communication, and by restricted and repetitive behavior. These signs all begin before a child is three years old. The autism spectrum disorders (ASD) also include the related conditions Asperger syndrome and PDD-NOS, which have fewer signs and symptoms.
Autism has a strong genetic basis, although the genetics of autism are complex and it is unclear whether ASD is explained more by multigene interactions or by rare mutations. In rare cases, autism is strongly associated with agents that cause birth defects. Other proposed causes, such as childhood vaccines, are controversial, and the vaccine hypotheses lack any convincing scientific evidence and are biologically implausible. The prevalence of ASD is about 6 per 1,000 people, with about four times as many males as females. (more…)
