Some characteristics of a population of mentally retarded young adults in a British city. A basis for estimating some service needs.

A population of young people who are mentally retarded is described in terms of the frequency of various kinds and degrees of impairment--intellectual, physical and behavioural. The population consisted of all those born in 1951--1955 who were resident in a city in 1962 and who at any time during the school years had been placed in any mental retardation service. The prevalence of the mentally retarded as defined is sixteen per 1000. Age specific prevalence rates for the same population rise from age five, reach a plateau of fourteen per 1000 from ages ten to fifteen and then drop sharply for the post-school period to a rate of five to six per 1000. Classifications of physical impairment, seizure histories and behaviour disturbances are described. Percentages are given separately for those with each impairment and in combination for each individual. For the survivors at age twenty-two, 44 per cent had physical impairments, 26 per cent had a history of seizures and 46 per cent had experienced behaviour disturbances. Results are discussed in relation to service needs.