Autism

Today, common usage of the term autism refers to the following subset of clinical diagnoses falling under the Diagnostic and Statistics Manual, fourth edition, revised (American Psychiatric Association) heading of Pervasive Developmental Disorders: autistic disorder, Asperger's disorder, and pervasive developmental disorders not otherwise specified (PDD-NOS). However, some still reserve usage of the term autism to refer only to the diagnosis of autistic disorder. Because of the potential for confusion, most epidemiologists now prefer to use the term autism spectrum disorder (ASD) to refer to the group of three diagnoses collectively and rely on the specific DSM-IV-R term when referring to a specific diagnosis. The use of the term spectrum, however, should not be taken to imply that this is one etiology with gradations of severity. It is quite possible that the ASDs actually comprise a number of etiologically distinct conditions.

ASDs are neurodevelopmental disorders characterized by deficits in reciprocal social interaction and communication along with the presence of restricted, repetitive, and stereotyped patterns of behaviors, interests, or activities. Individuals with a clinical diagnosis of autistic disorder must have 6 of 12 core symptoms with at least 2 in the social interaction domain, at least 1 in each of the other two domains, and emergence of impairment prior to age 3. A PDD-NOS diagnosis requires some impairment in each of the three core domains where impairment in at least one of the domains does not meet criteria for autistic disorder. An Asperger's disorder diagnosis requires impairment in social interaction and the presence of restricted and repetitive behaviors or interests without communication impairment. In practice, children receiving Asperger's diagnoses typically have no overt language [Page 64]delays, but, in fact, they often have other deficits in communication. Approximately half of the children with ASDs have cognitive impairment (IQ ≤ 70). Children with Asperger's disorder tend to have average to above-average IQs, though this is not part of the formal diagnostic criteria. ASDs are approximately four times more common in boys than in girls. Children with ASDs often present with other medical symptoms, including GI dysfunction, disordered sleep, as well as sensory and motor issues. Etiologic or pathophysiologic mechanisms underlying any of the ASDs are yet to be confirmed, and no biological test is available that can inform diagnosis.

In research and specialty clinic settings, two diagnostic tools have become increasingly accepted: the Autism Diagnostic Observation Schedule (ADOS) and the Autism Diagnostic Interview—Revised (ADI-R). The ADOS involves direct observation of the child interacting with an assessor who creates multiple, standardized stimuli to elicit behavioral responses from the child. The ADI-R is an in-person interview of the primary caregiver and focuses on the child's behaviors in various types of settings and responses to certain types of social and emotional stimuli. These tools are less reliable in children less than 3 years of age, and new tools are currently being developed and validated to identify signs of ASD in younger children. In most community clinical settings today, diagnosis, though informed by standard instruments, is still typically based on judgment of a clinician following DSM-IV diagnostic criteria.

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