Autism is a
disorder of neural development
that is characterized by impaired
social interaction and
communication, and by restricted and
repetitive behavior. These signs all begin before a child is three
years old. Autism involves many parts of the
brain; how this occurs is not well understood.
The two other
autism spectrum
disorders (ASD) are
Asperger
syndrome, which lacks delays in cognitive development and
language, and
PDD-NOS, diagnosed when full
criteria for the other two disorders are not met.
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. In rare cases, autism is strongly associated with
agents that cause birth defects.
Controversies surround other
proposed environmental
causes, such
as
heavy metals,
pesticides or childhood
vaccines. Most evidence suggests the vaccine
hypotheses are biologically implausible and lacking convincing
scientific evidence. The
prevalence of
autism is about 1–2 per 1,000 people; the prevalence of ASD is
about 6 per 1,000, with about four times as many males as females.
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.
Parents usually notice signs in the first two years of their
child's life. The signs usually develop gradually, but some
autistic children first develop more normally and then
regress. Although early behavioral or
cognitive intervention can help autistic children gain self-care,
social, and communication skills, there is no known cure. Not many
children with autism live independently after reaching adulthood,
though some become successful. An
autistic culture
has developed, with some individuals seeking a cure and others
believing autism should be tolerated as a difference and not
treated as a disorder.
Characteristics
Autism is a highly variable
neurodevelopmental disorder that
first appears during infancy or childhood, and generally follows a
steady course without
remission. Overt symptoms gradually
begin after the age of six months, become established by age two or
three years, and tend to continue through adulthood, although often
in more muted form. 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. 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.
Social development
Social deficits distinguish autism and the related
autism spectrum disorders (ASD; see
Classification) from other
developmental disorders. 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".
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 are
more likely to communicate by manipulating another person's hand.
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. 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. Older
children and adults with ASD perform worse on tests of face and
emotion recognition.
Contrary to common beliefs, autistic children do not prefer being
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 their quality of life more
deeply.
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. 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.
Communication
About a third to a half of individuals with autism do not develop
enough natural speech to meet their daily communication needs.
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) or
reverse pronouns.
Joint attention seems to be necessary for
functional speech, and deficits in joint attention seem to
distinguish infants with ASD: for example, they may look at a
pointing hand instead of the pointed-at object, and they
consistently fail to point at objects in order to comment on or
share an experience. Autistic children may have difficulty with
imaginative play and with developing symbols into language.
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.
Repetitive behavior
Autistic individuals display many forms of repetitive or restricted
behavior, which the Repetitive Behavior Scale-Revised (RBS-R)
categorizes as follows.

A young boy with autism, and the
precise line of toys he made
- Stereotypy is
repetitive movement, such as hand flapping, making sounds, 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.
- 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. A 2007 study reported that self-injury at some
point affected about 30% of children with ASD.
No single repetitive behavior seems to be specific to autism, but
only autism appears to have an elevated pattern of occurrence and
severity of these behaviors.
Other symptoms
Autistic individuals may have symptoms that are independent of the
diagnosis, but that can affect the individual or the family.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 savant. Many individuals with ASD
show superior skills in perception and attention, relative to the
general population.
Sensory
abnormalities are found in over 90% of those with autism, and are
considered core features by some, although there is no good
evidence that sensory symptoms differentiate autism from other
developmental disorders. 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).An estimated
60%–80% of autistic people have motor signs that include
poor muscle tone,
poor
motor planning, and
toe walking; ASD
is not associated with severe motor disturbances.
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; 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; studies
report conflicting results, and the relationship between GI
problems and ASD is unclear.
At some point in childhood, about two-thirds of individuals with
ASD are affected by
sleep problems; these most
commonly include symptoms of
insomnia such
as difficulty in falling asleep, frequent
nocturnal awakenings, and early
morning awakenings. Sleep problems are associated with difficult
behaviors and family stress, and are often a focus of clinical
attention over and above the primary ASD diagnosis.
Parents of children with ASD have higher levels of stress. Siblings
of children with ASD report greater admiration of and less conflict
with the affected sibling than siblings of unaffected children or
those with Down syndrome; siblings of individuals with ASD have
greater risk of negative well-being and poorer sibling
relationships as adults.
Classification
Autism is one of the five
pervasive developmental
disorders (PDD), which are characterized by widespread
abnormalities of social interactions and communication, and
severely restricted interests and highly repetitive behavior. These
symptoms do not imply sickness, fragility, or emotional
disturbance.
Of the five PDD forms,
Asperger
syndrome is closest to autism in signs and likely causes;
Rett syndrome and
childhood disintegrative
disorder share several signs with autism, but may have
unrelated causes;
PDD not
otherwise specified (PDD-NOS; also called
atypical
autism) is diagnosed when the criteria are not met for a more
specific disorder. Unlike with autism, people with Asperger
syndrome have no substantial delay in
language development. The terminology
of autism can be bewildering, with autism, Asperger syndrome and
PDD-NOS often called the
autism spectrum disorders (ASD)
or sometimes the
autistic disorders, whereas autism itself
is often called
autistic disorder,
childhood
autism, or
infantile autism. In this article,
autism refers to the classic autistic disorder; in
clinical practice, though,
autism,
ASD, and
PDD are often used interchangeably. ASD, in turn, is a
subset of the broader autism
phenotype,
which describes individuals who may not have ASD but do have
autistic-like
traits, such as
avoiding eye contact.
The manifestations of autism cover a wide
spectrum, ranging from individuals with
severe impairments—who may be silent,
mentally disabled, and locked into hand
flapping and rocking—to high functioning individuals who may have
active but distinctly odd social approaches, narrowly focused
interests, and verbose,
pedantic
communication. Because the behavior spectrum is continuous,
boundaries between diagnostic categories are necessarily somewhat
arbitrary. Sometimes the syndrome is divided into low-, medium- or
high-functioning autism
(LFA, MFA, and HFA), based on
IQ thresholds, or
on how much support the individual requires in daily life; these
subdivisions are not standardized and are controversial. Autism can
also be divided into
syndromal and
non-syndromal autism; the syndromal autism is associated with
severe or profound
mental
retardation or a congenital syndrome with physical symptoms,
such as
tuberous sclerosis.
Although individuals with Asperger syndrome tend to perform better
cognitively than those with autism, the extent of the
overlap between Asperger syndrome, HFA, and non-syndromal
autism is unclear.
Some studies have reported diagnoses of autism in children due to a
loss of language or social skills, as opposed to a failure to make
progress, typically from 15 to 30 months of age. The validity of
this distinction remains controversial; it is possible that
regressive autism is a specific
subtype, or that there is a continuum of behaviors between autism
with and without regression.
Research into causes has been hampered by the inability to identify
biologically meaningful subpopulations and by the traditional
boundaries between the disciplines of
psychiatry,
psychology,
neurology and
pediatrics. Newer technologies such as
fMRI can help identify biologically relevant
phenotypes (observable traits) that can be viewed
on
brain scans, to help further
neurogenetic studies of autism. It has been
proposed to classify autism using genetics as well as behavior,
with the name
Type 1 autism denoting rare autism cases
that test positive for a mutation in the
CNTNAP2 gene.
Causes
It has long been presumed that there is a common cause at the
genetic, cognitive, and neural levels for autism's characteristic
triad of symptoms. However, there is increasing suspicion that
autism is instead a complex disorder whose core aspects have
distinct causes that often co-occur.
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 with major effects, or by rare multigene
interactions of common genetic variants. Complexity arises due to
interactions among multiple genes, the environment, and
epigenetic factors which do not change
DNA but are heritable and influence
gene expression. Studies of twins suggest
that
heritability is 0.7 for autism and
0.9 for the broader autism phenotype, and siblings of those with
autism are about 25 times more likely to be autistic than the
general population. However, most of the mutations that increase
autism risk have not been identified. Typically, autism cannot be
traced to a
Mendelian (single-gene)
mutation or to a single
chromosome abnormality like
fragile X syndrome, and none of the
genetic syndromes associated with ASDs has been shown to
selectively cause ASD. Numerous candidate genes have been located,
with only small effects attributable to any particular gene. The
large number of autistic individuals with unaffected family members
may result from
copy number
variations—spontaneous
deletions or
duplications in genetic material during
meiosis. Hence, a substantial fraction of
autism cases may be traceable to genetic causes that are highly
heritable but not inherited: that is, the mutation that causes the
autism is not present in the parental genome.
Some rare mutations may lead to autism by disrupting some
synaptic pathways, such as those involved with
cell adhesion. Gene replacement
studies in mice suggest that autistic symptoms are closely related
to later developmental steps that depend on activity in synapses
and on activity-dependent changes. All known
teratogens (agents that cause
birth defects) related to the risk of autism
appear to act during the first eight weeks from
conception, and though this does not
exclude the possibility that autism can be initiated or affected
later, it is strong evidence that autism arises very early in
development. Although evidence for other environmental causes is
anecdotal and has not been confirmed by reliable studies, extensive
searches are underway.
Environmental factors that have been
claimed to contribute to or exacerbate autism, or may be important
in future research, include certain foods,
infectious disease,
heavy metals,
solvents,
diesel exhaust,
PCBs,
phthalates and
phenols used in
plastic
products,
pesticides,
brominated flame retardants,
alcohol,
smoking,
illicit drugs,
vaccines, and
prenatal
stress. Parents may first become aware of autistic symptoms in
their child around the time of a routine vaccination, and this has
given rise to theories that vaccines or their preservatives cause
autism. Although these theories lack convincing scientific evidence
and are biologically implausible, parental concern about autism has
led to lower rates of
childhood
immunizations and higher likelihood of
measles outbreaks.
Mechanism
Autism's symptoms result from maturation-related changes in various
systems of the brain. How autism occurs is not well understood. Its
mechanism can be divided into two areas: the
pathophysiology of brain structures and
processes associated with autism, and the
neuropsychological linkages between brain
structures and behaviors. The behaviors appear to have multiple
pathophysiologies.
Pathophysiology
Unlike many other brain disorders such as
Parkinson's, autism does not have a clear
unifying mechanism at either the molecular, cellular, or systems
level; it is not known whether autism is a few disorders caused by
mutations converging on a few common molecular pathways, or is
(like intellectual disability) a large set of disorders with
diverse mechanisms. Autism appears to result from developmental
factors that affect many or all functional brain systems, and to
disturb the timing of brain development more than the final
product.
Neuroanatomical studies and
the associations with
teratogens strongly
suggest that autism's mechanism includes alteration of brain
development soon after conception. This anomaly appears to start a
cascade of pathological events in the brain that are significantly
influenced by environmental factors. Just after birth, the brain of
an autistic child grows faster than usual, followed by normal or
relatively slower growth in childhood. The early overgrowth seems
to be most prominent in areas underlying the development of higher
cognitive specialization. Hypotheses for the cellular and molecular
bases of pathological early overgrowth include the following:
Interactions between the
immune system
and the
nervous system begin early
during the
embryonic stage of
life, and successful neurodevelopment depends on a balanced immune
response. It is possible that aberrant immune activity during
critical periods of neurodevelopment is part of the mechanism of
some forms of ASD. Although some abnormalities in the immune system
have been found in specific subgroups of autistic individuals, it
is not known whether these abnormalities are relevant to or
secondary to autism's disease processes. As
autoantibodies are found in conditions other
than ASD, and are not always present in ASD, the relationship
between immune disturbances and autism remains unclear and
controversial.
Several
neurotransmitter
abnormalities have been detected in autism, notably increased blood
levels of
serotonin. Whether these cause
structural or behavioral abnormalities is unclear. Some data
suggest an increase in several
growth
hormones; other data argue for diminished
growth factors. Also, some
inborn errors of metabolism are
associated with autism but probably account for less than 5% of
cases.
The
mirror neuron system (MNS)
theory of autism hypothesizes that distortion in the development of
the MNS interferes with imitation and leads to autism's core
features of social impairment and communication difficulties. The
MNS operates when an animal performs an action or observes another
animal perform the same action. The MNS may contribute to an
individual's understanding of other people by enabling the modeling
of their behavior via embodied simulation of their actions,
intentions, and emotions. Several studies have tested this
hypothesis by demonstrating structural abnormalities in MNS regions
of individuals with ASD, delay in the activation in the core
circuit for imitation in individuals with Asperger syndrome, and a
correlation between reduced MNS activity and severity of the
syndrome in children with ASD. However, individuals with autism
also have abnormal brain activation in many circuits outside the
MNS and the MNS theory does not explain the normal performance of
autistic children on imitation tasks that involve a goal or
object.

Autistic individuals tend to use
different areas of the brain (yellow) for a movement task compared
to a control group (blue).
ASD-related patterns of low function and aberrant activation in the
brain differ depending on whether the brain is doing social or
nonsocial tasks.In autism there is evidence for reduced functional
connectivity of the
default network,
a large-scale brain network involved in social and emotional
processing, with intact connectivity of the
task-positive network, used in
sustained attention and goal-directed thinking. In people with
autism the two networks are not negatively correlated in time,
suggesting an imbalance in toggling between the two networks,
possibly reflecting a disturbance of
self-referential thought. A 2008
brain-imaging study found a specific pattern of signals in the
cingulate cortex which differs in
individuals with ASD.
The underconnectivity theory of autism hypothesizes that autism is
marked by underfunctioning high-level neural connections and
synchronization, along with an excess of low-level processes.
Evidence for this theory has been found in
functional neuroimaging studies on
autistic individuals and by a
brain wave
study that suggested that adults with ASD have local
overconnectivity in the
cortex and
weak functional connections between the
frontal lobe and the rest of the cortex. Other
evidence suggests the underconnectivity is mainly within each
hemisphere of the cortex and
that autism is a disorder of the
association cortex.
From studies based on
event-related potentials, transient
changes to the brain's electrical activity in response to stimuli,
there is considerable evidence for differences in autistic
individuals with respect to attention, orientiation to auditory and
visual stimuli, novelty detection, language and face processing,
and information storage; several studies have found a preference
for non-social stimuli. For example,
magnetoencephalography studies have
found evidence in autistic children of delayed responses in the
brain's processing of auditory signals.
Neuropsychology
Two major categories of
cognitive theories
have been proposed about the links between autistic brains and
behavior.
The first category focuses on deficits in
social cognition. The
empathizing–systemizing
theory postulates that autistic individuals can systemize—that
is, they can develop internal rules of operation to handle events
inside the brain—but are less effective at empathizing by handling
events generated by other agents. An extension, the extreme male
brain theory, hypothesizes that autism is an extreme case of the
male brain, defined psychometrically as individuals in whom
systemizing is better than empathizing; this extension is
controversial, as many studies contradict the idea that baby boys
and girls respond differently to people and objects.
These theories are somewhat related to the earlier
theory of mind approach, which hypothesizes
that autistic behavior arises from an inability to ascribe mental
states to oneself and others. The theory of mind hypothesis is
supported by autistic children's atypical responses to the
Sally–Anne test for reasoning about
others' motivations, and the mirror neuron system theory of autism
described in
Pathophysiology maps well to the
hypothesis. However, most studies have found no evidence of
impairment in autistic individuals' ability to understand other
people's basic emotions or goals; instead, data suggests that
impairments are found in understanding more complex social emotions
or in considering others' viewpoints.
The second category focuses on nonsocial or general processing.
Executive dysfunction
hypothesizes that autistic behavior results in part from deficits
in
working memory, planning,
inhibition, and other forms of executive
function. Tests of core executive processes such as eye movement
tasks indicate improvement from late childhood to adolescence, but
performance never reaches typical adult levels. A strength of the
theory is predicting stereotyped behavior and narrow interests; two
weaknesses are that executive function is hard to measure and that
executive function deficits have not been found in young autistic
children.
Weak central coherence
theory hypothesizes that a limited ability to see the big
picture underlies the central disturbance in autism. One strength
of this theory is predicting special talents and peaks in
performance in autistic people. A related theory—enhanced
perceptual functioning—focuses more on the superiority of locally
oriented and
perceptual operations in
autistic individuals. These theories map well from the
underconnectivity theory of autism.
Neither category is satisfactory on its own; social cognition
theories poorly address autism's rigid and repetitive behaviors,
while the nonsocial theories have difficulty explaining social
impairment and communication difficulties. A combined theory based
on multiple deficits may prove to be more useful.
Screening
About half of parents of children with ASD notice their child's
unusual behaviors by age 18 months, and about four-fifths notice by
age 24 months. As postponing treatment may affect long-term
outcome, any of the following signs is reason to have a child
evaluated by a specialist without delay:
- No babbling by 12 months.
- No gesturing (pointing, waving goodbye,
etc.) by 12 months.
- No single words by 16 months.
- No two-word spontaneous phrases (other than instances of
echolalia) by 24 months.
- Any loss of any language or social skills, at any age.
The
American Academy of
Pediatrics recommends that all children be
screened for ASD at the 18- and
24-month well-child doctor visits, using autism-specific formal
screening tests. In contrast, the UK National Screening Committee
recommends against screening for ASD in the general population,
because screening tools have not been fully validated and
interventions lack sufficient evidence for effectiveness. Screening
tools include the Modified Checklist for Autism in Toddlers
(M-CHAT), the Early Screening of Autistic Traits Questionnaire, and
the First Year Inventory; initial data on M-CHAT and its
predecessor CHAT on children aged 18–30 months suggests that it is
best used in a clinical setting and that it has low
sensitivity (many false-negatives) but
good
specificity (few
false-positives). It may be more accurate to precede these tests
with a broadband screener that does not distinguish ASD from other
developmental disorders. Screening tools designed for one culture's
norms for behaviors like eye contact may be inappropriate for a
different culture.
Genetic
screening for autism is generally still impractical.
Diagnosis
Diagnosis is based on behavior,
not cause or mechanism. Autism is defined in the
DSM-IV-TR as exhibiting at least six symptoms
total, including at least two symptoms of qualitative impairment in
social interaction, at least one symptom of qualitative impairment
in communication, and at least one symptom of restricted and
repetitive behavior. Sample symptoms include lack of social or
emotional reciprocity, stereotyped and repetitive use of language
or idiosyncratic language, and persistent preoccupation with parts
of objects. Onset must be prior to age three years, with delays or
abnormal functioning in either social interaction, language as used
in social communication, or symbolic or imaginative play. The
disturbance must not be better accounted for by
Rett syndrome or
childhood disintegrative
disorder.
ICD-10 uses essentially the
same definition.
Several diagnostic instruments are available. Two are commonly used
in autism research: the
Autism Diagnostic
Interview-Revised (ADI-R) is a semistructured parent interview,
and the
Autism
Diagnostic Observation Schedule (ADOS) uses observation and
interaction with the child. The
Childhood Autism Rating Scale
(CARS) is used widely in clinical environments to assess severity
of autism based on observation of children.
A
pediatrician commonly performs a
preliminary investigation by taking developmental history and
physically examining the child. If warranted, diagnosis and
evaluations are conducted with help from ASD specialists, observing
and assessing cognitive, communication, family, and other factors
using standardized tools, and taking into account any associated
medical conditions. A pediatric
neuropsychologist is often asked
to assess behavior and cognitive skills, both to aid diagnosis and
to help recommend educational interventions. A
differential diagnosis for ASD at
this stage might also consider
mental
retardation,
hearing
impairment, and a
specific language impairment
such as
Landau–Kleffner
syndrome. The presence of autism can make it harder to diagnose
coexisting psychiatric disorders such as
depression.
Clinical genetics evaluations are
often done once ASD is diagnosed, particularly when other symptoms
already suggest a genetic cause. Although genetic technology allows
clinical geneticists to link an estimated 40% of cases to genetic
causes, consensus guidelines in the U.S. and UK are limited to
high-resolution chromosome and
fragile X
testing. A
genotype-first model of
diagnosis has been proposed, which would routinely assess the
genome's copy number variations. As new genetic tests are developed
several ethical, legal, and social issues will emerge. Commercial
availability of tests may precede adequate understanding of how to
use test results, given the complexity of autism's genetics.
Metabolic and
neuroimaging tests are sometimes helpful, but
are not routine.
ASD can sometimes be diagnosed by age 14 months, although diagnosis
becomes increasingly stable over the first three years of life: for
example, a one-year-old who meets diagnostic criteria for ASD is
less likely than a three-year-old to continue to do so a few years
later. In the UK the National Autism Plan for Children recommends
at most 30 weeks from first concern to completed diagnosis and
assessment, though few cases are handled that quickly in practice.
A 2009 U.S. study found the average age of formal ASD diagnosis was
5.7 years, far above recommendations, and that 27% of children
remained undiagnosed at age 8 years. Although the symptoms of
autism and ASD begin early in childhood, they are sometimes missed;
years later, adults may seek diagnoses to help them or their
friends and family understand themselves, to help their employers
make adjustments, or in some locations to claim disability living
allowances or other benefits.
Underdiagnosis and overdiagnosis are problems in marginal cases,
and much of the recent increase in the number of reported ASD cases
is likely due to changes in diagnostic practices. The increasing
popularity of drug treatment options and the expansion of benefits
has given providers incentives to diagnose ASD, resulting in some
overdiagnosis of children with uncertain symptoms. Conversely, the
cost of screening and diagnosis and the challenge of obtaining
payment can inhibit or delay diagnosis. It is particularly hard to
diagnose autism among the
visually
impaired, partly because some of its diagnostic criteria depend
on vision, and partly because autistic symptoms overlap with those
of common blindness syndromes.
Management

A three-year-old with autism points to
fish in an aquarium, as part of an experiment on the effect of
intensive shared-attention training on language development.
The main goals of treatment are to lessen associated deficits and
family distress, and to increase quality of life and functional
independence. No single treatment is best and treatment is
typically tailored to the child's needs. Studies of interventions
have methodological problems that prevent definitive conclusions
about
efficacy. Although many
psychosocial interventions have some positive
evidence, suggesting that some form of treatment is preferable to
no treatment, the methodological quality of
systematic reviews of these studies has
generally been poor, their clinical results are mostly tentative,
and there is little evidence for the relative effectiveness of
treatment options. Intensive, sustained
special education programs and
behavior therapy early in life can help
children acquire self-care, social, and job skills, and often
improve functioning and decrease symptom severity and maladaptive
behaviors; claims that intervention by around age three years is
crucial are not substantiated. Available approaches include
applied behavior analysis
(ABA), developmental models,
structured
teaching,
speech and
language therapy,
social skills
therapy, and
occupational
therapy. Educational interventions have some effectiveness in
children: intensive ABA treatment has demonstrated effectiveness in
enhancing global functioning in preschool children and is
well-established for improving intellectual performance of young
children. Neuropsychological reports are often poorly communicated
to educators, resulting in a gap between what a report recommends
and what education is provided. It is not known whether treatment
programs for children lead to significant improvements after the
children grow up, and the limited research on the effectiveness of
adult residential programs shows mixed results.
Many medications are used to treat ASD symptoms that interfere with
integrating a child into home or school when behavioral treatment
fails. More than half of U.S. children diagnosed with ASD are
prescribed
psychoactive drugs or
anticonvulsants, with the most common
drug classes being
antidepressants,
stimulants, and
antipsychotics. Aside from antipsychotics,
there is scant reliable research about the effectiveness or safety
of drug treatments for adolescents and adults with ASD. A person
with ASD may respond atypically to medications, the medications can
have
adverse effects, and
no known medication relieves autism's core symptoms of social and
communication impairments. Experiments in mice have reversed or
reduced some symptoms related to autism by replacing or modulating
gene function after birth, suggesting the possibility of targeting
therapies to specific rare mutations known to cause autism.
Although many
alternative therapies and interventions are available, few are
supported by scientific studies. Treatment approaches have little
empirical support in
quality-of-life
contexts, and many programs focus on success measures that lack
predictive validity and real-world relevance. Scientific evidence
appears to matter less to service providers than program marketing,
training availability, and parent requests. Though most alternative
treatments, such as
melatonin, have only
mild adverse effects some may place the child at risk. A 2008 study
found that compared to their peers, autistic boys have
significantly thinner bones if on
casein-free diets; in 2005, botched
chelation therapy killed a
five-year-old child with autism.
Treatment is expensive; indirect costs are more so. For someone
born in 2000, a U.S. study estimated an average lifetime cost of $
(
net present value in dollars,
inflation-adjusted from 2003 estimate ), with about 10%
medical care, 30% extra education and other
care, and 60% lost economic productivity. Publicly supported
programs are often inadequate or inappropriate for a given child,
and unreimbursed out-of-pocket medical or therapy expenses are
associated with likelihood of family financial problems; one 2008
U.S. study found a 14% average loss of annual income in families of
children with ASD, and a related study found that ASD is associated
with higher probability that
child care
problems will greatly affect parental employment. U.S. states
increasingly require private health insurance to cover autism
services, shifting costs from publicly funded education programs to
privately funded health insurance. After childhood, key treatment
issues include residential care, job training and placement,
sexuality, social skills, and
estate
planning.
Prognosis
There is no known cure. Children recover occasionally, so that they
lose their diagnosis of ASD; this occurs sometimes after intensive
treatment and sometimes not. It is not known how often recovery
happens; reported rates in unselected samples of children with ASD
have ranged from 3% to 25%. A few autistic children have acquired
speech at age 5 or older. Most children with autism lack
social support, meaningful relationships,
future employment opportunities or
self-determination. Although core
difficulties tend to persist, symptoms often become less severe
with age. Few high-quality studies address long-term
prognosis. Some adults show modest improvement in
communication skills, but a few decline; no study has focused on
autism after midlife. Acquiring language before age six, having an
IQ above 50, and having a marketable skill all
predict better outcomes;
independent
living is unlikely with severe autism. A 2004 British study of
68 adults who were diagnosed before 1980 as autistic children with
IQ above 50 found that 12% achieved a high level of independence as
adults, 10% had some friends and were generally in work but
required some support, 19% had some independence but were generally
living at home and needed considerable support and supervision in
daily living, 46% needed specialist residential provision from
facilities specializing in ASD with a high level of support and
very limited autonomy, and 12% needed high-level hospital care. A
2005 Swedish study of 78 adults that did not exclude low IQ found
worse prognosis; for example, only 4% achieved independence. A 2008
Canadian study of 48 young adults diagnosed with ASD as
preschoolers found outcomes ranging through poor (46%), fair (32%),
good (17%), and very good (4%); 56% of these young adults had been
employed at some point during their lives, mostly in volunteer,
sheltered or
part-time work. Changes in
diagnostic practice and increased availability of effective early
intervention make it unclear whether these findings can be
generalized to recently diagnosed children.
Epidemiology
Most recent
reviews tend to estimate a
prevalence of 1–2 per 1,000 for autism and close to 6 per 1,000 for
ASD; because of inadequate data, these numbers may underestimate
ASD's true prevalence.
PDD-NOS's prevalence
has been estimated at 3.7 per 1,000, Asperger syndrome at roughly
0.6 per 1,000, and
childhood disintegrative
disorder at 0.02 per 1,000. The number of reported cases of
autism increased dramatically in the 1990s and early 2000s. This
increase is largely attributable to changes in diagnostic
practices, referral patterns, availability of services, age at
diagnosis, and public awareness, though unidentified environmental
risk factors cannot be ruled out. The available evidence does not
rule out the possibility that autism's true prevalence has
increased; a real increase would suggest directing more attention
and funding toward changing environmental factors instead of
continuing to focus on genetics.
Boys are at higher risk for ASD than girls. The sex ratio averages
4.3:1 and is greatly modified by cognitive impairment: it may be
close to 2:1 with mental retardation and more than 5.5:1 without.
Although the evidence does not implicate any single
pregnancy-related risk factor as a cause of autism, the risk of
autism is associated with advanced age in either parent, and with
diabetes, bleeding, and use of psychiatric drugs in the mother
during pregnancy. The risk is greater with older fathers than with
older mothers; two potential explanations are the known increase in
mutation burden in older sperm, and the hypothesis that men marry
later if they carry genetic liability and show some signs of
autism. Most professionals believe that race, ethnicity, and
socioeconomic background do not affect the occurrence of
autism.
Autism is associated with several other conditions:
- Genetic
disorders. About 10–15% of autism cases have an
identifiable Mendelian (single-gene)
condition, chromosome
abnormality, or other genetic syndrome, and ASD is associated
with several genetic disorders.
- Mental
retardation. The fraction of autistic individuals who
also meet criteria for mental retardation has been reported as
anywhere from 25% to 70%, a wide variation illustrating the
difficulty of assessing autistic intelligence. For ASD other than
autism, the association with mental retardation is much
weaker.
- Anxiety
disorders are common among children with ASD; there
are no firm data, but studies have reported prevalences ranging
from 11% to 84%. Many anxiety disorders have symptoms that are
better explained by ASD itself, or are hard to distinguish from
ASD's symptoms.
- Epilepsy, with
variations in risk of epilepsy due to age, cognitive level, and
type of language disorder.
- Several metabolic
defects, such as phenylketonuria, are associated with
autistic symptoms.
- Minor physical
anomalies are significantly increased in the autistic
population.
- Preempted diagnoses. Although the DSM-IV rules
out concurrent diagnosis of many other conditions along with
autism, the full criteria for ADHD, Tourette syndrome, and other of these
conditions are often present and these comorbid diagnoses are
increasingly accepted.
History
A few examples of autistic symptoms and treatments were described
long before autism was named. The
Table Talk of
Martin Luther contains the story of a
12-year-old boy who may have been severely autistic. According to
Luther's notetaker
Mathesius,
Luther thought the boy was a soulless mass of flesh
possessed by the devil, and suggested
that he be suffocated. The earliest well-documented case of autism
is that of Hugh Blair of Borgue, as detailed in a 1747 court case
in which his brother successfully petitioned to annul Blair's
marriage to gain Blair's inheritance. The
Wild Boy of Aveyron, a
feral child caught in 1798, showed several signs
of autism; the medical student
Jean Itard treated him with a
behavioral program designed to help him form social attachments and
to induce speech via imitation.
The
New Latin word autismus (English
translation autism) was coined by the Swiss
psychiatrist
Eugen Bleuler in 1910 as he was
defining symptoms of schizophrenia. He derived it from the
Greek word
autós (αὐτός, meaning
self), and used
it to mean morbid self-admiration, referring to "autistic
withdrawal of the patient to his fantasies, against which any
influence from outside becomes an intolerable disturbance".
The word
autism first took its modern sense in 1938 when Hans Asperger of the Vienna
University Hospital
adopted Bleuler's terminology autistic
psychopaths in a lecture in German about child psychology. Asperger was
investigating an ASD now known as
Asperger syndrome, though for various
reasons it was not widely recognized as a separate diagnosis until
1981.
Leo Kanner of the
Johns Hopkins
Hospital
first used autism in its modern sense in
English when he introduced the label early infantile
autism in a 1943 report of 11 children with striking
behavioral similarities. Almost all the characteristics
described in Kanner's first paper on the subject, notably "autistic
aloneness" and "insistence on sameness", are still regarded as
typical of the autistic spectrum of disorders. It is not known
whether Kanner derived the term independently of Asperger.
Kanner's reuse of
autism led to decades of confused
terminology like
infantile schizophrenia, and child
psychiatry's focus on maternal deprivation led to misconceptions of
autism as an infant's response to "
refrigerator mothers". Starting in the
late 1960s autism was established as a separate syndrome by
demonstrating that it is lifelong, distinguishing it from mental
retardation and schizophrenia and from other developmental
disorders, and demonstrating the benefits of involving parents in
active programs of therapy. As late as the mid-1970s there was
little evidence of a genetic role in autism; now it is thought to
be one of the most heritable of all psychiatric conditions.
Although the rise of parent organizations and the destigmatization
of childhood ASD have deeply affected how we view ASD, parents
continue to feel
social stigma in
situations where their autistic children's behaviors are perceived
negatively by others, and many
primary care physicians and
medical specialists still express some
beliefs consistent with outdated autism research. The
Internet has helped autistic individuals bypass
nonverbal cues and emotional sharing that they find so hard to deal
with, and has given them a way to form online communities and work
remotely.
Sociological and
cultural aspects of autism have developed: some in the
community seek a cure, while others believe that autism is simply
another way of being.
References
- This paper represents a consensus of representatives from nine
professional and four parent organizations in the U.S.
- Validity of ASD subtypes: * *
- A partial update is in:
- Vaccines and autism: * * * *
- MNS and autism: * *
- Lack of research on drug treatments: * *
- Lack of support for interventions: * * *
- The quote is a translation of Bleuler's 1910 original.
- Reprinted in
External links