Autism is a form of neurodevelopmental disorder among the autism spectrum disorders. It is characterized by impaired development of social interactions and communication, both verbal and non-verbal. There is a lack of spontaneous acts of communication; both receptive and expressed, as well as speech disorders. A person diagnosed with autism will also demonstrate a limited range of activities and interests, while forming and maintaining relationships with peers. Individuals will exhibit limited interests, often very focused and repetitive. He or she is likely to be very routine-oriented and may exhibit behavioral symptoms such as hyperactivity, impulsivity, aggression, and self-injurious behaviors. There is no single known cause of autism. Researchers are investigating a number of possible theories, including genetics, heredity, medical problems, problems during pregnancy or childbirth, and environmental influences. It is widely believed to be caused by abnormalities in the structure or function of the brain. Neuropathological studies have shown that autism originates from abnormal brain development early in prenatal life, which continues after birth, showing accelerated brain growth measured by head circumference (Zwaigenbaum, L., Bryson , S., Rogers, T., Roberts, W., Brian, J. and Szatmari, P., 2005). The disorder also appears to have a genetic basis, although researchers have not yet found the specific genes linked to the onset of autism. There could be a group of genes that interfered in some way with normal brain development and function. Studies show that twins of children with autism were themselves more likely to have autism than the general population, demonstrating that there is a hereditary link...... middle of paper ......, Tager -Flusberg, H., & Lainhart, JE (2006). Comorbid psychiatric disorders in autistic children: development of interviews and rates of disorders. Journal of Autism and Developmental Disabilities, 36(7), 849-861.Orsmond, GI, Krauss, MW, & Seltzer, MM (2004). Peer relationships and social and recreational activities among adolescents and adults with autism. Journal of Autism and Developmental Disabilities, 34(3), 245-256. Seltzer, M.M., Shattuck, P., Abbeduto, L., & Greenberg, J.S. (2004). Developmental trajectory in autistic adolescents and adults. Reviews of Research in Mental Retardation and Developmental Disabilities, 10(4), 234-247. Zwaigenbaum, L., Bryson, S., Rogers, T., Roberts, W., Brian, J. and Szatmari, P. (2005) . Behavioral manifestations of autism during the first year of life. International Journal of Developmental Neuroscience, 23(2), 143-152.