Diagnostic/genetic studies in mental retardation.

Excluding environmental, psychotic, and unclassified categories, a total of 1,231 cases of severe mental retardation were found in the Central Wisconsin Center study. Some 45% of cases were estimated to be genetically caused or predisposed, but in only 15% was the risk of recurrence considered high. Nevertheless, I feel strongly that parents of all retarded patients deserve etiologic/diagnostic counseling.