The diagnostic labels and criteria for autism and similar disorders have changed several times since "autism" was first defined more than 50 years ago. The diagnostic criteria for autism that are currently most widely accepted within the US are those listed below, as specified in the American Psychiatric Association Diagnostic and Statistical Manual for Mental Disorders, Fourth Edition, commonly referred to as "DSM-IV."
DSM IV-TR Diagnostic Criteria for Autistic Disorder
A diagnosis of autistic disorder is made when the following criteria from A, B, and C are all met.
A total of six (or more) items from (1), (2), and (3), with at least two from (1), and one each from (2) and (3):
Qualitative impairment in social interaction, as manifested by at least two of the following:
marked impairment in the use of multiple nonverbal behaviors such as eye-to-eye gaze, facial expression, body postures, and gestures to regulate social interaction
failure to develop peer relationships appropriate to developmental level
a lack of spontaneous seeking to share enjoyment, interests, or achievements with others (e.g., by a lack of showing, bringing, or pointing out objects of interest)
lack of social or emotional reciprocity
Qualitative impairments in communication as manifested by at least one of the following:
delay in, or total lack of, the development of spoken language (not accompanied by an attempt to compensate through alternative modes of communication such as gesture or mime)
in individuals with adequate speech, marked impairment in the ability to initiate or sustain a conversation with others
stereotyped and repetitive use of language or idiosyncratic language
lack of varied, spontaneous make-believe play or social imitative play appropriate to developmental level
Restricted, repetitive, and stereotyped patterns of behavior, interest, and activities, as manifested by at least one of the following:
encompassing preoccupation with one or more stereotyped and restricted patterns of interest that is abnormal either in intensity or focus
apparently inflexible adherence to specific, nonfunctional routines or rituals
stereotyped and repetitive motor mannerisms (e.g., hand or finger flapping or twisting, or complex whole-body movements)
persistent preoccupation with parts of objects
Delays or abnormal functioning in at least one of the following areas, with onset prior to age 3 years: (1) social interaction, (2) language as used in social communication, or (3) symbolic or imaginative play.
The disturbance is not better accounted for by Rett's Disorder or Childhood Disintegrative Disorder.