Autism is often referred to as a "spectrum disorder," meaning that the symptoms and characteristics of autism can present themselves in a variety of combinations ranging from extremely mild to quite severe.
Autistic Disorder is classified within the spectrum of Pervasive Developmental Disorders. "These are characterized by severe and pervasive impairments in several areas of development: reciprocal social interaction skills, communication skills, or the presence of stereotyped behavior, interests, and activities. The qualitative impairments that define these conditions are distinctly deviant relative to the individual’s develop-mental level or mental age…" (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, 1994). Other Pervasive Developmental Disorders include Rett’s Disorder, Childhood Disintegrative Disorder, Asperger’s Disorder, and Pervasive Developmental Disorder Not Otherwise Specified.
According to the Autism Society of America, "Autism is a severely incapacitating, lifelong, developmental disability that typically appears during the first three years of life." The result of a neurological disorder that affects the functioning of the brain, autism and its behavioral symptoms occur in approximately 15 out of every 10,000 births. Autism is four times more common in boys than in girls. It has been found throughout the world in families of all racial, ethnic, and social backgrounds.