The modern term "autism" was originated by Leo Kanner in the 1940's. In "Autistic Disturbances of Affective Contact" (1943), he described a group of autistic children; he viewed them as much more similar to one another than to schizophrenics, with whom they generally had been associated. Until that time, the classical definition for autism (still seen in some dictionaries) was "a form of childhood schizophrenia characterized by acting out and withdrawal from reality." Kanner believed that these children represented an entirely different clinical psychiatric disorder. He noted four main symptoms associated with the disease: social withdrawal or "extreme autistic alone-ness"; either muteness or failure to use spoken language "to convey meaning to others"; an "obsessive desire for maintenance of sameness"; and preoccupation with highly repetitive play habits, producing "severe limitation of spontaneous activity." Kanner also noted that autism—unlike other types of childhood psychoses—began in or near infancy and had both cognitive and affective components.
Over the years, several attempts have been made to establish precise diagnostic criteria for autism. Among the criteria given in the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (rev. 4th ed., 2000, DSM-IV-TR) are pervasive lack of responsiveness to other people; gross deficits in language development; if speech is present, peculiar patterns (such as echolalia and pronoun reversals); bizarre reaction to environmental aspects (resistance to change); and the absence of any symptoms of schizophrenia. These criteria are largely a restatement of Kanner's viewpoint.
The prevalence of autism is generally estimated at between 3 to 9 percent of the population of the United States. Study of the sex distribution shows that it is 2.5 to 4 times as common in males as in females. The causes of autism have not been conclusively determined, although the possibilities are wide-ranging and said to be rooted in both biology and environment. As an example of the latter, one of the most widely cited causes has been vaccination, particularly the mumps, measles, and rubella (MMR) vaccine that is given at approximately eighteen months of age and often corresponds with the earliest detected symptoms of autism. Still, researchers in the United States and Europe have determined that this vaccine does not cause autism, based on the fact that vaccination rates held steady throughout the 1990's at almost 97 percent of children, yet the rate of autism diagnosis increased sevenfold during the same time period.
Possible physiological causes include genetics (siblings of autistic children are two hundred times more likely than the general population to be diagnosed with autism themselves), neurochemistry (abnormal levels of the neurotransmitters norepinephrine, serotonin, and dopamine have been established in children with autism as well as their relatives), low birth weight, older mothers, and brain abnormalities such as reduction of tissue in the cerebellum and enlarged ventricles in the cerebrum.
Largely because of Kanner's original sample (now known to have been atypical), many people believe that autistic children come from professional families. Subsequent studies have indicated that this is not so. Rather, autistic children come from families within a wide socioeconomic range, and more than 75 percent of them score in the moderately mentally retarded range on intelligence tests prior to or in the absence of effective treatment.
The behavior that characterizes the autistic personality strongly suggests that the disorder is related to other types of neurologic dysfunction. Identified neurological correlations include soft neurologic signs (such as poor coordination), seizure disorders (such as phenylketonuria), abnormal electroencephalograms, and unusual sleep patterns. This emphasis on neuro-logic—or organic—explanations for autism is relatively new; autism was previously thought to be an entirely emotional disorder.
The difficulties that autistic children show in social relationships are exhibited in many ways. Most apparent is a child's failure to form social bonds. For example, such youngsters rarely initiate any interactions with other children. Moreover, unlike nonautistic children, they do not seek parental company or run to parents for solace when distressed. Many sources even point to frequent parental statements that autistic children are not as "cuddly" as normal babies and do not respond to their mothers or to affectionate actions. Autistic children avoid direct eye contact and tend to look through or past other people. In addition, autistic children rarely indulge in any cooperative play activities or strike up close friendships with peers.
Sometimes speech does not develop at all. When speech development does occur, it is very slow and may even disappear again. Another prominent
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