Are the Majority of Children With Autism Mentally Retarded? A Systematic Evaluation of the Data/INVITED COMMENTARY: "Are the Majority of Children With Autism Mentally Retarded?"/INVITED COMMENTARY: "Are the Majority of Children With Autism Mentally Retarded?"

There are frequent claims in the literature that a majority of children with autism are mentally retarded (MR). The present study examined the evidence used as the basis for these claims, reviewing 215 articles published between 1937 and 2003. Results indicated 74% of the claims came from nonempirical sources, 53% of which never traced back to empirical data. Most empirical evidence for the claims was published 25 to 45 years ago and was often obtained utilizing developmental or adaptive scales rather than measures of intelligence. Furthermore, significantly higher prevalence rates of MR were reported when these measures were used. Overall, the findings indicate that more empirical evidence is needed before conclusions can be made about the percentages of children with autism who are mentally retarded. [PUBLICATION ABSTRACT]