The definition of autism is based on the diagnostic criteria provided in the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders - Fourth Edition (DSM - IV.)

Autism is included under DSM-IV's pervasive developmental disorders. This is a category of disorders in which many basic areas of infant and child psychological development are affected at the same time, and to a severe degree.

Autistic disorder has three major hallmarks: qualitative impairment in social interaction, qualitative impairment in communication, and restricted, repetitive and stereotypical patterns of behavior, interests, and activities. Onset in delays is very early, prior to three years of age.

To meet DSM-IV diagnostic criteria for autism, children will display impairment in social interaction in at least two ways, impairment in communication in at least one way, and restricted, repetitive and stereotypical patterns of behavior, interests and activities in at least one way.

According to DSM-IV, impairment in social interaction is manifested in at least two of the following ways:

a. 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;

b. failure to develop peer relationships appropriate to developmental level;

c. a lack of spontaneous seeking to share enjoyment, interests or achievement with other people;

d. lack of social or emotional reciprocity.

Impairment in communication is manifested by at least one of the following:

a. delay in, or total lack of, the development of spoken language, not accompanied by an attempt to compensate through alternative modes of communication;

b. in individuals with adequate speech, marked impairment in the ability to initiate or sustain conversation with others;

c. stereotyped and repetitive use of language or idiosyncratic language, and

d. lack of varied, spontaneous make-believe play or social imitative play appropriate to developmental level.

Restricted, repetitive and stereotyped patterns of behavior, interests and activities are 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 of focus;

· apparently inflexible adherence to specific, non-functional routines or rituals; stereotyped and repetitive motor mannerisms, such as hand or finger flapping, or complex whole body movements;

· persistent preoccupation with parts of objects.
(DSM-IV, 1994).

Autism and PDD: What's the Difference?
Pervasive Developmental Disorders (PDD) as defined in the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition (DSM-IV) is a category of disorders incorporating extreme developmental abnormalities with onset in the first three years of life. Pervasive Developmental Disorder represents a distortion in basic development with characteristic features including:

o Severe and pervasive impairment in reciprocal social interaction;
o Severe and pervasive impairment in communication skills; and
o Presence of stereotyped behavior, interests and activities.

"Basic psychological functions such as attention, mood, intellectual functioning and motor movement are affected at the same time, and to a severe degree." (Rapoport & Ismond, 1996).

Within the broad classification of PDD are five subtypes: Autistic Disorder, Asperger's Disorder, Rett's Disorder, Childhood Disintegrative Disorder and PDD-Not Otherwise Specified (PDD-NOS).

Autistic Disorder is the best studied of the PDD subtypes. To be diagnosed as autistic, children must display impairment in social interaction in at least two ways, impairment in communication in at least one way, and restricted, repetitive and stereotypical patterns of behavior, interests and activities in at least one way. (See Definition of Autism.)

Asperger's Disorder is characterized by severe and sustained impairment in social interaction combined with restricted, repetitive and stereotyped patterns of behavior, interests and activities (DSM-IV, 1994). This disorder differs from autism in that "few clinically significant delays in language or cognitive development are apparent, and self-help and adaptive behaviors often appear normal." (Rapoport & Ismond, 1996).

Rett's Disorder is the only subtype of PDD which occurs exclusively in females. In this disorder, development seems normal through the first five months of life, followed by deceleration of head growth, loss of previously acquired purposeful hand skills with subsequent development of stereotyped hand movements, loss of social engagement, appearance of poorly coordinated gait or trunk movements, and severely impaired expressive and receptive language, (DSM-IV, 1994).

Childhood Disintegrative Disorder is characterized by development that appears normal through the first two years of life. Following this, abnormalities develop in at least two of the following areas: social interaction, communication, and restricted, repetitive, stereotyped patterns of behavior, interests, and activities. In addition, there is clinically significant loss of previously acquired skills (before age 10), in at least two of the following areas: expressive or receptive language, social skills or adaptive behavior, bowel or bladder control, play, and motor skills. (DSM-IV, 1994).

The category of PDD-NOS is used when there is severe and pervasive impairment in the development of reciprocal social interaction and verbal and nonverbal communication skills, or when stereotyped behavior, interests and activities are present, but symptoms do not meet the criteria for other disorders. (DSM-IV, 1994).

Typically, Pervasive Developmental Disorders are extremely incapacitating, and their symptoms are chronic and lifelong (although this is less the case for Asperger's Disorder). "Factors considered most important for determining prognosis are IQ levels, and development of social and language skills" (Rapoport & Ismond, 1996). Identification of variables that predict outcomes reliably continue to undergo intense study within the scientific community. Given the chronic nature of PDD, however, long-term treatment is typically required.

References/Definition of Autism
American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders (4th ed.). Washington, DC: Author.

Autism Society of Maine. (No date). Autism. [Brochure]. Gardiner, ME: Author.

Klinger, L. & Dawson, G. (1996). Autistic disorder. In Marsh, E. & Barkley, R. (eds.), Child Psychopathy (pp 311 - 339). New York: Gilford Press.

Maurice, C. (1993). Let me hear your voice. New York: Knopf.

Perry, R., Cohen, I., & DeCarlo, R. (1995). Case study: Deterioration, autism, and recovery in two siblings. Journal of the American Academy of Child and Adolescent Psychiatry, 34, 232 - 237.

Rapoport, J.L. & Ismond, D.R. (1996). DSM-IV training guide for diagnosis of childhood disorders. New York: Brunner/Mazel.