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The term autism was first used in 1943 by Leo Kanner to describe a syndrome of “disturbances in affective contact,” which he observed in 11 boys who lacked the dysmorphology often seen in mental retardation, but who were missing the social motivation toward communication and interaction that is typically present even in children with severe intellectual deficits. Despite their obvious impairments in social communication, the children Kanner observed did surprisingly well on some parts of IQ tests, leading Kanner to believe they did not have mental retardation.
Kanner's observation about intelligence has been modified by subsequent research. When developmentally appropriate, individually administered IQ testing is administered, approximately 80% of people with autism score in the mentally retarded range, and scores remain stable over time (Rutter et al., 1994). However, individuals with autism do show unusual scatter in their abilities, with nonverbal, visually based performance often significantly exceeding verbal skills; unlike the performance seen in children with other kinds of retardation, whose scores are comparable across all kinds of tasks.
Recent research on the genetics of autism suggests that there are heritable factors that may convey susceptibility (Rutter et al., 1997). This vulnerability may be expressed in a range of social, communicative, and cognitive difficulties expressed in varying degrees in parents, siblings, and other relatives of individuals with autism.
Although genetic factors appear to contribute to some degree to the appearance of autism, the condition can also be associated with other medical conditions. Dykens and Volkmar (1997) reported the following:
• Approximately 25% of individuals with autism develop seizures.
• Tuberous sclerosis (a disease characterized by abnormal tissue growth) is associated with autism with higher than expected prevalence.
• The co-occurrence of autism and fragile X syndrome (the most common heritable form of mental retardation) is also higher than would be expected by chance.
Autism is considered one of a class of disabilities referred to as pervasive developmental disorders, according to the Diagnostic and Statistical Manual of the American Psychiatric Association (4th ed., 1994). The diagnostic criteria for autism are more explicitly stated in DSM-IV than the criteria for other pervasive developmental disorders. The criteria for autism are the result of a large field study conducted by Volkmar et al. (1994). The field trial showed that the criteria specified in DSM-IV exhibit reliability and temporal stability. Similar research on diagnostic criteria for other pervasive developmental disorders is not yet available.
The primary diagnostic criteria for autism include the following:
Early onset
Many parents first become concerned at the end of the first year of life, when a child does not start talking. At this period of development, children with autism also show reduced interest in other people; less use of communicative gestures such as pointing, showing, and waving; and noncommunicative sound making, perhaps including echoing that is far in advance of what can be produced in spontaneous or meaningful contexts. There may also be unusual preoccupations with objects (e.g., an intense interest in vacuum cleaners) or actions (such as twanging rubber bands) that are not like the preoccupations of other children at this age.
Impairment in social interaction
This is the hallmark of the autistic syndrome. Children with autism do not use facial expressions, eye contact, body posture, or gestures to engage in social interaction as other children do. They are less interested in sharing attention to objects and to other people, and they rarely attempt to direct others' attention to objects or events they want to point out. They show only fleeting interest in peers, and often appear content to be left on their own to pursue their solitary preferred activities.
Impairment in communication
Language and communicative difficulties are also core symptoms in autism. Communicative differences in autism include the following:
• Mutism. Approximately half of people with autism never develop speech. Nonverbal communication, too, is greatly restricted (Paul, 1987). The range of communicative intentions expressed is limited to requesting and protesting. Showing off, labeling, acknowledging, and establishing joint attention, seen in normal preverbal children, are absent in this population. Wants and needs are expressed preverbally, but forms for expression are aberrant. Some examples are pulling a person toward a desired object without making eye contact, instead of pointing, and the use of maladaptive and self-injurious behaviors to express desires (Donnellan et al., 1984). Pointing, showing, and turn-taking are significantly reduced.
• For people with autism who do develop speech, both verbal and nonverbal forms of communication are impaired. Forty percent of people with autism exhibit echolalia, an imitation of speech they have heard—either immediate echolalia, a direct parroting of speech directed to them, or delayed echolalia, in which they repeat snatches of language they have heard earlier, from other people or on TV, radio, and so on. Both kinds of echolalia are used to serve communicative functions, such as responding to questions they do not understand (Prizant and Duchan, 1981). Echolalia decreases, as in normal development, with increases in language comprehension.
A significant delay in comprehension is one of the strongest distinctions between people with autism and those with other developmental disabilities (Rutter, Maywood, and Howlin, 1992). Formal aspects of language production are on par with developmental level. Children with autism are similar to mental age–matched children in the acquisition of rule-governed syntax, but language development lags behind nonverbal mental age (Lord and Paul, 1997). Articulation is on par with mental age in children with autism who speak; however, high-functioning adults with autism show higher than expected rates of speech distortions (Shriberg et al., 2001).
Word use is a major area of deficit in those who speak (Tager-Flusberg, 1995). Words are assigned to the same categories that others use (Minshew and Goldsein, 1993), and scores on vocabulary tests are often a strength. However, words may be used with idiosyncratic meanings, and difficulty is seen with deictic terms (i.e., you/I, here/there), whose meaning changes, depending on the point of view of the speaker). This was first thought to reflect a lack of self, as evidenced by difficulty with saying I. More recent research suggests that the flexibility required to shift referents and difficulty assessing others' state of knowledge are more likely to account for this observation (Lee, Hobson, and Chiat, 1994).
Pragmatic, interpersonal uses of language present the greatest challenges to speakers with autism. The rate of initiation of communication is low (Stone and Caro-Martinez, 1990), and speech is often idiosyncratic and contextually inappropriate (Lord and Paul, 1997). Few references are made to mental states, and people with autism have difficulty inferring the mental states of others (Tager-Flusberg, 1995). Deficits are seen in providing relevant responses or adding new information to established topics; primitive strategies such as imitation are used to continue conversations (Tager-Flusberg and Anderson, 1991).
For individuals at the highest levels of functioning, conversation is often restricted to obessive interests. There is little awareness of listeners' lack of interest in extended talk about these topics. Difficulty is seen in adapting conversation to take into account all participants' purposes. Very talkative people with autism are impaired in their ability to use language in functional, communicative ways (Lord and Paul, 1997), unlike other kinds of children with language impairments, whose language use improves with increased amount of speech.
Paralinguistic features such as voice quality, intonation, and stress are frequently impaired in speakers with autism. Monotonic intonation is one of the most frequently recognized aspects of speech in autism. It is a major contributor to listeners' perception of oddness (Mesibov, 1992). The use of pragmatic stress in spontaneous speech and speech fluency are also impaired (Shriberg et al., 2001).
Stereotypic patterns of behavior
Abnormal preoccupations with objects or parts of objects are characteristic of autism, as is a need for routines and rituals always to be carried out in precisely the same way. Children with autism become exceedingly agitated over small changes in routine. Stereotyped motor behaviors, such as hand flapping, are also typical but are related to developmental level and are likely to emerge in the preschool period.
Delays in imaginative play
Children with autism are more impaired in symbolic play behaviors than in other aspects of cognition, although strengths are seen in constructive play, such as stacking and nesting (Schuler, Prizant, and Wetherby, 1997).
There is no medical or biological profile that can be used to diagnose autism, nor is there one diagnostic test that definitely identifies this syndrome. Current assessment methods make use primarily of multidimensional scales, either interview or observational, that provide separate documentation of aberrant behaviors in each of the three areas that are known to be characteristic of the syndrome: social reciprocity, communication, and restricted, repetitive behaviors. The most widely used for research purposes are the Autism Diagnostic Interview (Lord, Rutter, and Le Conteur, 1994) and the Autism Diagnostic Observation Scale (Lord et al., 2000).
Until recently, autism was thought to be a rare disorder, with prevalence estimates of 4–5 per 10,000 (Lotter, 1966). However, these prevalence figures were based on identifying the disorder in children who, like the classic patients described by Kanner, had IQs within normal range. As it became recognized that the social and communicative deficits characteristic of autism could be found in children along the full range of the IQ spectrum, prevalence estimates rose to 1 per 1000 (Bryson, 1997).
Currently, there is a great deal of debate about incidence and prevalence, particularly about whether incidence is rising significantly. Although clinicians see more children today who receive a label of autism than they did 10 years ago, this is likely to be due to a broadening of the definition of the disorder to include children who show some subset of symptoms without the full-blown syndrome. Using this broad definition, current prevalence estimates range from 1 in 500 to as low as 1 in 300 (Fombonne, 1999). Although there is some debate about the precise ratio, autism is more prevalent in males than in females (Bryson, 1997).
In the vast majority of cases, children with autism grow up to be adults with autism. Only 1%–2% of cases have a fully normal outcome (Paul, 1987). The classic image of the autistic child—mute or echolalic, with stereotypic behaviors and a great need to preserve sameness—is most characteristic of the preschool period. As children with autism grow older, they generally progress toward more, though still aberrant, social involvement. In adolescence, 10%–35% of children with autism show some degree of regression (Gillberg and Schaumann, 1981). Still, with continued intervention, growth in both language and cognitive skills can be seen (Howlin and Goode, 1998).
Approximately 75% of adults with autism require high degrees of support in living, with only about 20% gainfully employed (Howlin and Goode, 1998). Outcome in adulthood is related to IQ, with good outcomes almost always associated with IQs above 60 (Rutter, Greenfield, and Lockyer, 1967). The development of functional speech by age 5 is also a strong predictor of good outcome (DeMyer et al., 1973).
Major changes have taken place in the treatments used to address autistic behaviors. Although a variety of pharmacological agents have been tried, and some are effective at treating certain symptoms (see McDougle, 1997, for a review), the primary forms of treatment for autism are behavioral and educational. Early intervention, when provided with a high degree of intensity (at least 20 hours per week), has proved particularly effective (Rogers, 1996). There is ongoing debate about the best methods of treatment, particularly for lower functioning children. There are proponents of operant applied behavior treatments (Lovaas, 1987), of naturalistic child-centered approaches (Greenspan and Wieder, 1997), and of approaches that are some hybrid of the two (Prizant and Wetherby, 1998). Recent innovations focus on the use of alternative communication systems (e.g., Bondi and Frost, 1998) and on the use of environmental compensatory supports, such as visual calendars, to facilitate communication and learning (Quill, 1998). Although all of these approaches have been shown to be associated with growth in young children with autism, no definitive study has yet compared approaches or measured long-term change.
For higher functioning and older individuals with autism, most interventions are derived from more general strategies used in children with language impairments. These strategies focus on the development of conversational skills, the use of scripts to support communication, strategies for communicative repair, and the use of reading to support social interaction (Prizant et al., 1997). “Social stories,” in which anecdotal narratives are encouraged to support social understanding and participation, is a new method that is often used with higher functioning individuals (Gray, 1995).
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