[Epidemiological study of mental retardation in 12 districts of China].
D000293:Adolescent; D000328:Adult; D002648:Child; D002681:China; D003710:Demography; D005260:Female; D006801:Humans; D008607:Intellectual Disability / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D012931:Social Environment; D011795:Surveys and Questionnaires