A study of institutionalized mentally retarded patients in Manitoba. I: Classification and preventability.

This preliminary report concerns the types, and the possibility of prevention, of mental retardation found among 406 patients less than 20 years of age and with IQs less than or equal to 50 who had been admitted to institutions for the retarded in Manitoba prior to 1977. The retardation appeared to be of genetic origin in 27.8 per cent of cases, and acquired in a further 30.3 per cent. 31 per cent of the genetic and 55 per cent of the acquired, or 25.4 per cent of the total group, are considered to have been avoidable, given the full application of current techniques and knowledge.