Autism is one of five disorders under the umbrella of Pervasive Developmental Disorders (PDD), a general category of disorders, which are characterized by severe and pervasive impairment in several areas of development (Autism Society of America, n.d.). "The five disorders under PDD are Autistic Disorder, Asperger's Disorder, Childhood Disintegrative Disorder, Rett's Disorder, and PDD-Not Otherwise Specified" (Autism Society of America, n.d.). Individuals who fall under the PDD category exhibit commonalities in communication and social deficits but differ in terms of severity. Autism is the most common of the PDD, affecting as many as one in every two hundred fifty individuals (Prater, 2002.). This means that as many as 1.5 million Americans today are believed to have some form of autism and it is costing the nation over thirteen billion dollars a year (Blacher, 2002). Autism is more common than Down Syndrome, Multiple Sclerosis or Cystic Fibrosis, and yet, autism research still receives less than five percent of the funding of these other diseases (Prater, 2002).
While the understanding of autism has grown tremendously since it was first described by Leo Kanner in 1943, many professionals in the medical, educational, and vocational fields are still unaware of how autism affects people and how they can effectively work with individuals with autism (ASA, n.d.). Autism is a broad-spectrum disorder and the symptoms and characteristics can present themselves in a wide variety of combinations, from mild to severe. Although autism is defined by a certain set of behaviors, children and adults can exhibit any combination of the behaviors in any degree of severity. Every person with autism is an individual, and like all individuals, has a unique personality and combination of characteristics. Some individuals are only affected mildly in some areas and more severe in others. People with autism process and respond to information in unique ways.