![]() National Alliance on Mental Illness page printed from http://www.nami.org/ (800) 950-NAMI; info@nami.org ©2013 Diagnostic OverviewSince the causes for Autism Spectrum Disorders are unknown, an ASD diagnosis is based purely on observations or behavioral reports. In contrast to other medical syndromes, ASDs are not diseases: They are developmental disorders that reflect differences in the way that children develop from very early on to adulthood. Within the category of ASDs, there are a number of different levels of severity. Autism is recognized as receiving the most attention in the area of study. It is defined by difficulties in three areas; social deficits, communication problems, and repetitive or restricted behaviors, with the onset beginning by the age of three. Asperger Syndrome is a form of ASD that is often identified later than the age of three and usually after the age of five. It is associated with the social symptoms of autism and some repetitive interests or behaviors, but not with language or mental delays. Rett Syndrome and Child Disintegrative Disorder (CDD) are both rare forms of ASD that have specific patterns of onset. Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS) is a form of ASD used to describe individuals who meet criteria for autism in terms of social difficulties but not in both communication and restricted, repetitive behaviors. This label is often used by professionals when they are not quite sure of a diagnosis or when the symptoms are mild. Several studies have been reported that several more children have PDD-NOS or less clear symptoms as have classic autism.
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