Autism is a brain development disorder that impairs social interaction and communication and causes restricted and repetitive behavior, all starting before a child is three years old. The genetics of autism are complex and it is generally unclear which genes are responsible for it. Autism affects many parts of the brain but how this occurs is also poorly understood. Autism is strongly associated with agents that cause birth defects. Other proposed causes, such as childhood vaccines, are controversial and the vaccine hypotheses lack convincing scientific evidence. The number of people known to have autism has increased dramatically since the 1980s. Parents usually notice signs in the first two years of their child’s life. Early behavioral cognitive intervention can help children gain self-care, social, and communication skills but there is no cure for it. Few children with autism live independently after reaching adulthood, but the same become successful and an autistic culture has developed, with some seeking a cure and others believing that autism is a condition rather than a disorder.