AUTISM

a neurobiological disorder that affects physical, social, and language skills. The term was first used by the psychiatrist Leo Kanner in the 1940s to describe children who appeared to be excessively withdrawn and self-preoccupied. The syndrome usually appears before 2 1/2 years of age, though the earliest signs are quite subtle. Autistic infants appear indifferent or averse to affection and physical contact, though attachment to parents or certain adults often develops later. Speech develops slowly and abnormally (it is often atonal and arrhythmic) or not at all. It may be characterized by meaningless, noncontextual echolalia (constant repetition of what is said by others) or the replacement of speech by strange mechanical sounds. Inappropriate attachment to objects may occur. There may be underemphasized reaction to sound, no reaction to pain, or no recognition of genuine danger, yet autistic children are extremely sensitive. Usually the syndrome is accompanied by an obsessive desire to prevent environmental change, and frequently, rhythmic body movements such as rocking or hand-clapping. About 25 percent of autistic children develop seizures by late adolescence. Estimates of the prevalence of autism range from 1 to 15 per 10,000 children; some 15 to 20 percent are able to become socially and vocationally independent. The disorder is about three to four times more common in males. Autism is still incompletely understood. It was earlier thought that postnatal factors, such as behavioral interactions between parents and child, were responsible for the infant's abnormal development. Recent research using magnetic resonance imaging (MRI) has revealed abnormalities in the brain structure (particularly the cerebellum and the limbic system) of autistic individuals, abnormalities likely to have occurred during early brain development. Researchers also have noted a deficiency of large nerve cells called Purkinje cells and an excess of serotonin, a neurotransmitter. There is no effective treatment for autism.