<unk>  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. This set of signs distinguishes<unk>  from milder<unk>  spectrum disorders (ASD) such as Asperger syndrome.<unk>  has a strong genetic basis, although the genetics of<unk>  are complex and it is unclear whether ASD is explained more by multigene interactions or by rare mutations. In rare cases,<unk>  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. Most recent reviews estimate a prevalence of 100- 200 cases per 100,000 people for<unk> , and about 600 per 100,000 for ASD, with ASD averaging a 4.3:1 male-to-female ratio. The number of people known to have<unk>  has increased dramatically since the 1980s, at least partially due to changes in diagnostic practice; the question of whether actual prevalence has increased is unresolved.<unk>  affects many parts of the brain; how this occurs is poorly understood. Parents usually notice signs in the first two years of their child's life. Early behavioral or cognitive intervention can help children gain self-care, social, and communication skills. There is no cure. Few children with<unk>  live independently after reaching adulthood, but some become successful, and an<unk> ic culture has developed, with some seeking a cure and others believing that<unk>  is a condition rather than a disorder.
Autism
Selective mutism
Taurodontism
Mental retardation
Attention-deficit hyperactivity disorder
High-functioning autism
Language delay
Chronic tic disorder