The essential features of Autistic Disorder are the presence of markedly abnormal or impaired development in social interaction and communication and a markedly restricted repertoire of activity and interests.   Manifestations of the disorder vary greatly depending on the developmental level and chronological age of the individual.   Autistic Disorder is sometimes referred to as early infantile autism, childhood autism, or Kanner's autism.

     The impairment in reciprocal social interaction is gross and sustained.   There may be marked impairment in the use of multiple nonverbal behaviors (e.g., eye-to-eye gaze, facial expression, body postures and gestures) to regulate social interaction and communication (Criterion A1a).   There may be failure to develop peer relationships appropriate to developmental level (Criterion A1b) that may take different forms at different ages.   Younger individuals may have little or no interest in establishing friendships.   Older individuals may have an interest in friendship but lack understanding of the conventions of social interaction.   There may be a lack of spontaneous seeking to share enjoyment, interests, or achievements with other people (e.g.,not showing, bringing, or pointing out objects they find interesting)(Criterion A1c).   Lack of social or emotional reciprocity may be present (e.g.,not actively participating in simple social play or games, preferring solitary activities, or involving others in activities only as tools or "mechanical" aids)(Criterion A1d)   Often an individual's awareness of others is markedly impaired.   Individuals with this disorder may be oblivious to other children (including siblings), may have no concept of the needs of others, or may not notice another person's distress.

     The impairment in communication is also marked and sustained and affects both verbal and nonverbal skills.   There may be delay in, or total lack of, the development of spoken language (Criterion A2a).   In individuals who do speak, there may be marked impairment in the ability to initiate or sustain a conversation with others (Criterion A2b), or a stereotyped and repetitive use of language or idiosyncratic language (Criterion A2c).   There may also be a lack of varied, spontaneous make-believe play or social imitative play appropriate to developmental level (Criterion A2d).   When speech does develop, the pitch, intonation, rate, rhythm, or stress may be abnormal (e.g.,tone of voice may be monotonous or inappropriate to context or may contain questionlike rises at ends of statements).   Grammatical structures are often immature and include stereotyped and repetitive use of language (e.g.,repetition of words or phrases regardless of meaning; repeating jingles or commercials) or idiosyncratic language (i.e.,language that has meaning only to those familiar with the individual's communication style).   Language comprehension is often very delayed, and the individual may be unable to understand simple questions or directions.   A disturbance in the pragmatic (social use) of language is often evidenced by an inability to integrate words with gestures or understand humor or nonliteral aspects of speech such as irony or implied meaning.   Imaginative play is often absent or markedly impaired.   These individuals also tend not to engage in the simple imitation games or routines of infancy or early childhood or do so only out of context or in a mechanical way.