Prevalence Of Autism
There is much controversy concerning the prevalence of autism. DSM-IV notes a prevalence rate of 4 to 5 cases per 10,000 in the United States, though these data are based on diagnostic criteria from the third edition of theDSM, criteria that have been shown to be diagnostically more restrictive. Many investigators have suggested a prevalence rate for PDD of around 1 in 800 cases in the United States, but no definitive prevalence data exist for DSM-IV criteria. It is clear, however, that more cases are being diagnosed. Several possible influences include earlier detection, diagnosis of more mildly affected individuals, the use of autism rather than mental retardation as the primary diagnosis in cases of more severe mental retardation, and the preference for this diagnosis in geographic regions where it is associated with higher intensity delivery of services. According toDSM-IV, approximately 70 percent of individuals diagnosed with autism have also been diagnosed with mild to severe mental retardation.