Autism Spectrum Disorder (ASD)

A severe neurodevelopmental disorder that first appears in early childhood and is characterized by impaired social interaction and language development, and restricted and repetitive behaviors.

First described in 1943 by Leo Kanner (1894–1981), an Austrian-American physician, autism is a term used for a heterogeneous group of severe neurodevelopmental disorders that affect an estimated 1–2 children per thousand worldwide. Autism manifests itself in early childhood, most often before the age of three. Autistic children are impaired socially, in language development, and in behavior. This disorder is known as autism spectrum disorder (ASD), a term that is preferred as of 2015 to underscore the fact that the manifestations of the disorder lie on a spectrum of severity even though they share common features.

Major brain stru ctu re s implicated in autism

Major brain stru ctu re s implicated in autism

Contrary to earlier beliefs, ASDs are not thought to have psychological origins, such as inadequate parenting. Several possible causes have been proposed, including phenylketonuria (an inherited metabolic disease), exposure to rubella or certain chemicals in utero, and hereditary predisposition. Several genes associated with autism have been identified as of 2015, and the parents of a child diagnosed with autism have a 5% chance of having a second child with the disorder. The etiology of autism can be determined for only about 15%–20% of persons diagnosed with ASD; the cause remains unknown in the remaining 80%. There was no accurate clinical test for autism as of 2015, although CT scans of autistic children sometimes reveal abnormalities in the ventricles of the brain. In some cases the child may be given an electroencephalogram (EEG) to rule out seizure disorder.

ASDs are usually diagnosed in children between the ages of two and three years based on clinical observation and parental reports. Until this point, manifestations of the disorder are difficult to detect, and in some cases an autistic child will develop normally for the first year or two of life. However, a break usually occurs before the age of two and a half, when speech development (if it has begun) stops and social responses fail to develop. There are several checklists that can be administered to the child's parents or used by the pediatrician to screen young children for signs of an ASD. Children who are thought to show signs of an ASD on the basis of the pediatric checklist are then given a follow-up comprehensive evaluation by a team comprising several different specialists (typically a neurologist, a psychiatrist, a speech therapist, and a child psychologist).

Language difficulties are the single symptom that most often leads parents to seek diagnosis and help for autistic children. The development of spoken language is either delayed or totally absent in children with autism. Those who can speak still have trouble listening to others and initiating or carrying on a conversation. The speech of autistic persons often lacks normal grammatical structures and is also nonstandard in terms of such characteristics as pitch, speed, rhythm, or stress on syllables. Echolalia (echoing other people's voices or voices heard on television) is also common.

Besides social and language impairments, the other major symptom of autism is the presence of repetitive, ritualized patterns of behavior. These may be repeated physical movements, such as rocking, swaying, flapping one's arms, or clapping. Autistic behavior may also take such forms as arranging objects in specific patterns or quantities, mimicking a particular action, or performing a routine activity exactly the same way every day. Other behavioral characteristics associated with autism are a preoccupation with a single interest (often one for which a large number of facts may be collected); resistance to trivial changes in routine; fascination with a moving object (such as revolving doors) or a particular part of an object; and a strong attachment to an inanimate object. Persons with autism may exhibit oversensitivity to certain stimuli (such as light or touch), unusual pickiness in eating, inappropriate fear and/or fearlessness, and self-injuring behavior, such as head banging. As many as 25% of autistic children develop epileptic seizures later in life, often in adolescence, although this particular symptom appears only in those who are intellectually disabled.

Identified Prevalence of Autism Spectrum Disorder ADDM Network 2000-2010 (combining data from all sites)

Identified Prevalence of Autism Spectrum Disorder ADDM Network 2000-2010 (combining data from all sites)
Source: Division of Birth Defects, National Center on Birth Defects and Development Disabilities, Centers for Disease Control and Prevention


The automatic repetition of words or sounds made by another person.
Neurodevelopmental disorder—
A disorder caused by impairments in the growth and development of the central nervous system (brain and spinal cord). Autism spectrum disorders are one type of neurodevelopmental disorder.
A set of four interconnected cavities in the brain that produce and circulate cerebrospinal fluid.

Seventy percent of autistic children are diagnosed as intellectually disabled, and 60% have IQ scores below 50. However, many demonstrate skill in music, mathematics, long-term memorization of trivial data, and such specialized tasks as assembling jigsaw puzzles. Autistic children with IQ scores of 70 and above have the best prognosis for living and working independently as adults, although only one in six children with autism becomes a well-adjusted adult, with another 10% achieving a fair degree of adjustment. Even those autistic adults who function relatively well will still experience difficulty with social interaction and communication, and highly restricted interests and activities. They are also at increased risk of such mood disorders as depression and anxiety disorders across their lifespan.

Besides IQ, other predictors of future adjustment for autistic children are their degree of language development, the overall severity of their symptoms, and the types of treatment they receive. While psychotherapy has not been of value in treating persons with autism, behavior modification, medications, and dietary recommendations have been proven effective in controlling specific symptoms. Special education programs are able to improve the social interaction of autistic children and enhance their academic skills. Developmental work that includes parents has been found to be especially helpful.

See also Asperger syndrome ; Child development ; Neuropsychological tests .



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American Academy of Child and Adolescent Psychiatry (AACAP), 3615 Wisconsin Avenue, N.W., Washington, DC, United States, 20016-3007, (202) 966-7300, Fax: (202) 966-2891, .

Autism Society, 4340 East-West Hwy, Suite 350, Bethesda, MD, United States, 20814, (301) 657-0881, (800) 3AUTISM (328-8476),,

Autism Speaks, 1 East 33rd Street, Fourth Floor, New York, NY, United States, 10016, (212) 252-8584, (888) 2884762, Fax: (212) 252-8676,, .

National Institute of Neurological Disorders and Stroke (NINDS), P.O. Box 5801, Bethesda, MD, United States, 20824, (301) 496-5751, (800) 352-9424, ,