Autistic disorder is the best known of the pervasive developmental disorders. It is characterized by sustained impairments in reciprocal social interactions, communication deviance, and restricted, stereotypical behavioral patterns. According to DSM-IV, abnormal functioning in the above areas must be present by age 3 years. More than two thirds of autistic persons function on a retarded level.


  • Prevalence

Most of the epidemiological surveys have found rates of 4 to 5 out of 10,000. However, recent studies have found higher rates, which may be attributed to more thorough case ascertainment, more uniform (or perhaps broader) diagnostic criteria, and, in some studies, earlier age at assessment.

  • Sex ratio

The higher incidence of autism in boys than in girls has been well documented, with ratios of 2.6 to 1 common and ratios up to 4 to 1 found in some studies. Girls are often more severely affected than boys, however, and on average score lower on intelligence tests.


Early clues to the biological basis of autism included the high rate of associated mental retardation, the 4 to 1 male-female ratio, the increased incidence of seizure disorders, and the recognition that medical and genetic conditions such as congenital rubella and untreated phenylketonuria could be associated with the syndrome. It is now believed that autistic disorder is a behavioral syndrome that can be caused or influenced by diverse conditions that adversely affect the central nervous system (CNS). The biological abnormalities underlying the disorder are currently unknown, and most cases do not show an association with a known genetic or medical disorder or with obvious CNS damage.

One Response to Autism

  1. […] are not as reliable as those made in the preschool period, when many behaviors characteristic of autistic disorder are seen. The evaluation of autistic children requires a detailed prenatal and perinatal […]

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