Autism spectrum disorders (ASDs) are conditions in which people have difficulty developing normal social relationships, use language abnormally or not at all, and behave in compulsive and ritualistic ways.
Affected people have difficulty communicating with and relating to others.
People with an autism spectrum disorder also have restricted patterns of behavior, interests, and/or activities and often follow rigid routines.
Diagnosis is based on observation and the reports of parents and other caregivers.
Most people respond best to highly structured behavioral interventions.
Autism spectrum disorders are considered a spectrum (range) of disorders because the manifestations vary widely in type and severity. Previously, ASDs were subclassified into classic autism, Asperger syndrome, Rett syndrome, childhood disintegrative disorder, and pervasive developmental disorder not otherwise specified. However, doctors currently do not use this terminology and consider these all as ASDs (except for Rett syndrome, which is a distinct genetic disorder). ASDs are different from intellectual disability, although many people with ASDs have both. The classification system emphasizes that, within the broad spectrum, different features may occur more or less strongly in a given individual.
The estimated number of people identified with an autism spectrum disorder continues to rise as doctors and caregivers learn more about the symptoms of the disorder.
Symptoms of autism spectrum disorders may appear in the first 2 years of life, but in milder forms symptoms may not be detected until school age. These disorders occur in about 1 of 68 people based on recent population statistics and are 4 times more common among boys than among girls.
The specific causes of autism spectrum disorders are not fully understood, although they are often related to genetic factors. For parents of one child with an ASD, risk of having another child with an ASD is 50 to 100 times greater. Several genetic abnormalities, such as Fragile X syndrome and Down syndrome, may be associated with ASD. Prenatal infections, for example, viral infections such as rubella or cytomegalovirus (see Table: Some Infections of Newborns), may also play a role. It is clear, however, that ASDs are not caused by poor parenting, adverse childhood conditions, or vaccinations.