Autistic Spectrum Disorders occur in approximately 1% of the population. The characteristics related to these disorders are present from early childhood and negatively impact the child's or adult's everyday functioning. Autistic spectrum disorders are characterized by deficits in social communication and social interactions across multiple settings; and individuals demonstrate or engage in restricted, repetitive behaviors, interests, or activities. Individuals may also display motor deficits, which could be characterized by an odd gait, clumsiness, walking on tiptoes, etc. Self-injurious behaviors such as head banging or biting on self are not unusual aspects.
Social communication and social interaction deficits are demonstrated by a child's or adult's, inability to engage in reciprocal communication, perspective take or the inability to view things from another's perspective, demonstrate or interpret nonverbal communication behaviors, and appropriately adapt one's behavior across social circumstances or settings.
Restricted, repetitive patterns of behaviors, interests or activities are demonstrated by stereotypic or repetitive motor movements, use of objects, or speech. Additionally, the child or adult demonstrates an inflexible adherence to ritualized patterns of verbal or nonverbal behaviors; restricted, obsessive interests that are abnormal in intensity or focus; and/or over/under-reactions to sensory input or unusual interest in sensory aspects of the environment.
Source: Diagnostic and Statistical Manual of Mental and Emotional Disorders-V