Autism Characteristics

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. This set of signs distinguishes autism from milder autism spectrum disorders (ASD) such as Asperger syndrome.[1]

Autism is highly heritable, although the genetics of autism are complex and it is generally unclear which genes are responsible.[2] In rare cases, autism is strongly associated with agents that cause birth defects.[3] Other proposed causes, such as childhood vaccines, are controversial and the vaccine hypotheses lack convincing scientific evidence.[4] Most recent reviews estimate a prevalence of one to two cases per 1,000 people for autism, and about six per 1,000 for ASD, with ASD averaging a 4.3:1 male-to-female ratio. The number of people known to have autism has increased dramatically since the 1980s, at least partly due to changes in diagnostic practice; the question of whether actual prevalence has increased is unresolved.[5]

Autism 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.[6] Few children with autism live independently after reaching adulthood, but some become successful,[7] and an autistic culture has developed, with some seeking a cure and others believing that autism is a condition rather than a disorder.[8]

Autism is distinguished by a pattern of symptoms rather than one single symptom. The main characteristics are impairments in social interaction, impairments in communication, restricted interests and repetitive behavior. Other aspects, such as atypical eating, are also common but are not essential for diagnosis.[22] Individual symptoms of autism occur in the general population and appear not to associate highly, without a sharp line separating pathological severity from common traits.[23]

Social development

People with autism have social impairments and often lack the intuition about others that many people take for granted. Noted autistic Temple Grandin described her inability to understand the social communication of neurotypicals as leaving her feeling "like an anthropologist on Mars".[24]

Social impairments become apparent early in childhood and continue through adulthood. Autistic infants show less attention to social stimuli, smile and look at others less often, and respond less to their own name. Autistic toddlers have more striking social deviance; for example, they have less eye contact and anticipatory postures and are more likely to communicate by manipulating another person's hand.[21] Three- to five-year-old autistic children are less likely to exhibit social understanding, approach others spontaneously, imitate and respond to emotions, communicate nonverbally, and take turns with others. However, they do form attachments to their primary caregivers.[25] They display moderately less attachment security than usual, although this feature disappears in children with higher mental development or less severe ASD.[26] Older children and adults with ASD perform worse on tests of face and emotion recognition.[27]

Contrary to common belief, autistic children do not prefer to be alone. Making and maintaining friendships often proves to be difficult for those with autism. For them, the quality of friendships, not the number of friends, predicts how lonely they are.[28]

There are many anecdotal reports, but few systematic studies, of aggression and violence in individuals with ASD. The limited data suggest that in children with mental retardation, autism is associated with aggression, destruction of property, and tantrums. Dominick et al. interviewed the parents of 67 children with ASD and reported that about two-thirds of the children had periods of severe tantrums and about one-third had a history of aggression, with tantrums significantly more common than in children with a history of language impairment.[29]

Communication

About a third to a half of individuals with autism do not develop enough natural speech to meet their daily communication needs.[30] Differences in communication may be present from the first year of life, and may include delayed onset of babbling, unusual gestures, diminished responsiveness, and the desynchronization of vocal patterns with the caregiver. In the second and third years, autistic children have less frequent and less diverse babbling, consonants, words, and word combinations; their gestures are less often integrated with words. Autistic children are less likely to make requests or share experiences,