by : Uta Frith
Autism is rare. According to the strict criteria applied by Kanner, it appears in four of every 10,000 births. With the somewhat wider criteria used in current diagnostic practice, the incidence is much higher: one or two in 1,000 births, about the same as Down’s syndrome. Two to four times as many boys as girls are affected.
For many years, autism was thought to be a purely psychological disorder without an organic basis. At first, no obvious neurological problems were found. The autistic children did not necessarily have low intellectual ability, and they often looked physically normal. For these reasons, psychogenic theories were proposed and taken seriously for many years. They focused on the idea that a child could become autistic because of some existentially threatening experience. A lack of maternal bonding or a disastrous experience of rejection, so the theory went, might drive an infant to withdraw into an inner world of fantasy that the outside world never penetrates.
These theories are unsupported by any empirical evidence. They are unlikely to be supported because there are many instances of extreme rejection and deprivation in childhood, none of which have resulted in autism. Unfortunately, therapies vaguely based on such notions are still putting pressure on parents to accept a burden of guilt for the supposedly avoidable and reversible breakdown of interpersonal interactions. In contrast, well-structured behavior modification programs have often helped families in the management of autistic children, especially children with severe behavior problems. Such programs do not claim to reinstate normal development in the children.
The insupportability of the psychogenic explanation of autism led a number of workers to search for a biological cause. Their efforts implicate a defective structure in the brain, but that structure has not yet been identified. The defect is believed to affect the thinking of autistic people, making them unable to evaluate their own thoughts or to perceive clearly what might be going on in someone else’s mind.
Autism appears to be closely associated with several other clinical and medical conditions. They include maternal rubella and chromosomal abnormality, as well as early injury to the brain and infantile seizures. Most impressive, perhaps, are studies showing that autism can have a genetic basis. Both identical twins are much more likely to be autistic than are both fraternal twins. Moreover, the likelihood that autism will occur twice in the same family is 50 to 100 times greater than would be expected by chance alone.
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