Autism affects information processing in the brain by altering how nerve cells and their synapses connect and organize.² Autism is one of three recognized disorders in the autism spectrum, the other two being Asperger syndrome and pervasive developmental disorder.² Autism has a strong genetic basis, although the genetics of autism are complex and not well understood.²
In rare cases, autism is associated with agents that cause birth defects. Some of these include heavy metals, pesticides, or childhood vaccines (2). The prevalence of autism is about 1 per 1,000 people worldwide and the Center for Disease Control and Prevention (CDC) reports that 20 per 1,000 children in the United States were diagnosed with autism disorders in 2012.²
Autism first appears during infancy or childhood and generally follows a steady course without remission. Overt symptoms begin after about six months and become established by age three. The symptoms continue to adulthood but usually in a more muted form.²
Individuals with autism have trouble with social development. People with autism have social impairments and often lack the intuition about others that many people take for granted. For example, a person with autism would not be able to tell ‘a bad person’ from a ‘good person’ unlike an individual without autism. Additionally, autistic infants show less attention to social stimuli, smile and look at others less, and respond to their own name less.²
Individuals with autism also have trouble with communication. A third to one half of individuals with autism do not develop enough natural speech to meet their daily communication needs.² Autistic children are less likely to make requests or share experiences but more likely to repeat others’ words. Autistic individuals score better on tests in vocabulary and spelling than non-autistic individuals but worse in complex language, comprehension, and figurative language.²
Lastly, autistic individuals often display repetitive language. Individuals with autism often display stereotypy, compulsive behavior, ritualistic behavior, and self-injury. No single repetitive or self-injurious behavior seems to be specific to autism, but only autism appears to have an elevated pattern of occurrence and severity of these behaviors.³
2. Levy SE, Mandell DS, Schultz RT. Autism. Lancet. 2009: 374 (9701): 1627-38.
3. Bodfish JW, Symons FJ, Parker DE, Lewis MH. Varieties of Repetitive Behavior in Autism: Comparisons to Mental Retardation. J Autism Dev Disord. 2000: 30 (3): 237-43.
Image source: Becky Wetherington on Flickr