Autism is a
disorder of neural development characterized by impaired
social interaction and
communication, and by restricted and repetitive behavior. The diagnostic criteria require that symptoms become apparent before a child is three years old.
[2] Autism affects information processing in the
brain by altering how nerve cells and their
synapses connect and organize; how this occurs is not well understood.
[3] It is one of three recognized disorders in the
autism spectrum (ASDs), the other two being
Asperger syndrome, which lacks delays in cognitive development and language, and
pervasive developmental disorder, not otherwise specified (commonly abbreviated as PDD-NOS), which is diagnosed when the full set of criteria for autism or Asperger syndrome are not met.
[4]
Autism has a strong genetic basis, although the
genetics of autism are complex and it is unclear whether ASD is explained more by rare
mutations, or by rare combinations of common genetic variants.
[5] In rare cases, autism is strongly associated with
agents that cause birth defects.
[6] Controversies surround other proposed environmental
causes, such as
heavy metals,
pesticides or childhood
vaccines;
[7] the vaccine hypotheses are biologically implausible and lack convincing scientific evidence.
[8] The
prevalence of autism is about 1–2 per 1,000 people worldwide, and the
Centers for Disease Control and Prevention (CDC) report 11 per 1,000 children in the United States are diagnosed with ASD as of 2008.
[7][9][10] The number of people diagnosed with autism has increased dramatically since the 1980s, partly due to changes in diagnostic practice; the question of whether actual prevalence has increased is unresolved.
[11]
Parents usually notice signs in the first two years of their child's life.
[12] The signs usually develop gradually, but some autistic children first develop more normally and then
regress.
[13] Early behavioral or cognitive intervention can help autistic children gain self-care, social, and communication skills.
[12] Although there is no known cure,
[12] there have been reported cases of children who recovered.
[14] Not many children with autism live independently after reaching adulthood, though some become successful.
[15] An
autistic culture has developed, with some individuals seeking a cure and others believing autism should be accepted as a difference and not treated as a disorder.
[16]
Characteristics
Autism is a highly variable
neurodevelopmental disorder[17] that first appears during infancy or childhood, and generally follows a steady course without
remission.
[18] Overt symptoms gradually begin after the age of six months, become established by age two or three years,
[19] and tend to continue through adulthood, although often in more muted form.
[20] It is distinguished not by a single symptom, but by a characteristic triad of symptoms: impairments in social interaction; impairments in communication; and restricted interests and repetitive behavior. Other aspects, such as atypical eating, are also common but are not essential for diagnosis.
[21] Autism's individual symptoms occur in the general population and appear not to associate highly, without a sharp line separating pathologically severe from common traits.
[22]
Social development
Social deficits distinguish autism and the related
autism spectrum disorders (ASD; see
Classification) from other developmental disorders.
[20] People with autism have social impairments and often lack the intuition about others that many people take for granted. Noted autistic
Temple Grandin described her inability to understand the
social communication of
neurotypicals, or people with normal
neural development, as leaving her feeling "like an anthropologist on Mars".
[23]
Unusual social development becomes apparent early in childhood. Autistic infants show less attention to social stimuli, smile and look at others less often, and respond less to their own name. Autistic toddlers differ more strikingly from
social norms; for example, they have less
eye contact and turn taking, and do not have the ability to use simple movements to express themselves, such as the deficiency to point at things.
[24] Three- to five-year-old autistic children are less likely to exhibit social understanding, approach others spontaneously, imitate and respond to emotions, communicate nonverbally, and take turns with others. However, they do form
attachments to their primary caregivers.
[25] Most autistic children display moderately less
attachment security than non-autistic children, although this difference disappears in children with higher mental development or less severe ASD.
[26] Older children and adults with ASD perform worse on tests of face and emotion recognition.
[27]
Children with high-functioning autism suffer from more intense and frequent loneliness compared to non-autistic peers, despite the common belief that children with autism prefer to be alone. Making and maintaining friendships often proves to be difficult for those with autism. For them, the quality of friendships, not the number of friends, predicts how lonely they feel. Functional friendships, such as those resulting in invitations to parties, may affect the quality of life more deeply.
[28]
There are many anecdotal reports, but few systematic studies, of aggression and violence in individuals with ASD. The limited data suggest that, in children with mental retardation, autism is associated with aggression, destruction of property, and
tantrums. A 2007 study interviewed parents of 67 children with ASD and reported that about two-thirds of the children had periods of severe tantrums and about one-third had a history of aggression, with tantrums significantly more common than in non-autistic children with language impairments.
[29] A 2008 Swedish study found that, of individuals aged 15 or older discharged from hospital with a diagnosis of ASD, those who committed violent crimes were significantly more likely to have other psychopathological conditions such as
psychosis.
[30]
Communication
About a third to a half of individuals with autism do not develop enough natural speech to meet their daily communication needs.
[31] Differences in communication may be present from the first year of life, and may include delayed onset of
babbling, unusual gestures, diminished responsiveness, and vocal patterns that are not synchronized with the caregiver. In the second and third years, autistic children have less frequent and less diverse babbling, consonants, words, and word combinations; their gestures are less often integrated with words. Autistic children are less likely to make requests or share experiences, and are more likely to simply repeat others' words (
echolalia)
[32][33] or
reverse pronouns.
[34] Joint attention seems to be necessary for functional speech, and deficits in joint attention seem to distinguish infants with ASD:
[4] for example, they may look at a pointing hand instead of the pointed-at object,
[24][33] and they consistently fail to point at objects in order to comment on or share an experience.
[4] Autistic children may have difficulty with imaginative play and with developing symbols into language.
[32][33]
In a pair of studies, high-functioning autistic children aged 8–15 performed equally well as, and adults better than, individually matched controls at basic language tasks involving vocabulary and spelling. Both autistic groups performed worse than controls at complex language tasks such as figurative language, comprehension and inference. As people are often sized up initially from their basic language skills, these studies suggest that people speaking to autistic individuals are more likely to overestimate what their audience comprehends.
[35]
Repetitive behavior
Autistic individuals display many forms of repetitive or restricted behavior, which the Repetitive Behavior Scale-Revised (RBS-R)
[36] categorizes as follows.
A young boy with autism who has arranged his toys in row
- Stereotypy is repetitive movement, such as hand flapping, head rolling, or body rocking.
- Compulsive behavior is intended and appears to follow rules, such as arranging objects in stacks or lines.
- Sameness is resistance to change; for example, insisting that the furniture not be moved or refusing to be interrupted.
- Ritualistic behavior involves an unvarying pattern of daily activities, such as an unchanging menu or a dressing ritual. This is closely associated with sameness and an independent validation has suggested combining the two factors.[36]
- Restricted behavior is limited in focus, interest, or activity, such as preoccupation with a single television program, toy, or game.
- Self-injury includes movements that injure or can injure the person, such as eye poking, skin picking, hand biting, and head banging.[4] A 2007 study reported that self-injury at some point affected about 30% of children with ASD.[29]
No single repetitive or self-injurious behavior seems to be specific to autism, but only autism appears to have an elevated pattern of occurrence and severity of these behaviors.
[37]
Other symptoms
Autistic individuals may have symptoms that are independent of the diagnosis, but that can affect the individual or the family.
[21] An estimated 0.5% to 10% of individuals with ASD show unusual abilities, ranging from splinter skills such as the memorization of trivia to the extraordinarily rare talents of prodigious
autistic savants.
[38] Many individuals with ASD show superior skills in perception and attention, relative to the general population.
[39] Sensory abnormalities are found in over 90% of those with autism, and are considered core features by some,
[40] although there is no good evidence that sensory symptoms differentiate autism from other developmental disorders.
[41] Differences are greater for under-responsivity (for example, walking into things) than for over-responsivity (for example, distress from loud noises) or for sensation seeking (for example, rhythmic movements).
[42] An estimated 60%–80% of autistic people have motor signs that include
poor muscle tone,
poor motor planning, and
toe walking;
[40] deficits in motor coordination are pervasive across ASD and are greater in autism proper.
[43]
Unusual eating behavior occurs in about three-quarters of children with ASD, to the extent that it was formerly a diagnostic indicator. Selectivity is the most common problem, although eating rituals and food refusal also occur;
[29] this does not appear to result in
malnutrition. Although some children with autism also have
gastrointestinal (GI) symptoms, there is a lack of published rigorous data to support the theory that autistic children have more or different GI symptoms than usual;
[44] studies report conflicting results, and the relationship between GI problems and ASD is unclear.
[45]
Parents of children with ASD have higher levels of
stress.
[46] Siblings of children with ASD report greater admiration of and less conflict with the affected sibling than siblings of unaffected children and were similar to siblings of children with
Down syndrome in these aspects of the sibling relationship. However, they reported lower levels of closeness and intimacy than siblings of children with
Down syndrome; siblings of individuals with ASD have greater risk of negative well-being and poorer sibling relationships as adults.
[47]
.jpg)
.jpg)
.jpg)