The result of a neurological impairment that affects the functioning of the brain, autism and its associated behaviors occur in approximately 15 of every 10,000 individuals. Individuals with characteristics of what is now called autism have been identified throughout the world in families of all racial, ethnic, and socio-economic backgrounds. However, the disorder was not formally recognized until the 1940's, when Leo Kanner and Hans Asperger both independently coined the term autism. All PDD's overlap in that portions of their clinical features are shared, however, they are distinct disorders and are separately diagnosed. Autism, the most commonly diagnosed PDD, interferes with the typical development of the brain in the areas that control all aspects of communication, social interaction, and sensory development.
Autism is more common in males than females.
For those individuals diagnosed with autism, males are four times more likely to receive the diagnosis. The symptoms and characteristics of autism may present themselves in a wide variety of combinations, ranging from mild to severe. Although autism is defined by the presence of a certain set of behaviors, individuals with autism may exhibit any combination of these behaviors, varying in degree of severity. Therefore, two individuals with a diagnosis of autism may act very differently from one another. Autism is more common in some families than in others.