Prevalence of autism and related conditions in adults in a mental handicap hospital.

The proportions of subjects with severe social impairment and those retaining the features of childhood autism were investigated in a population of mentally retarded adults in a long-stay hospital. The results confirmed the findings of an earlier study of mentally retarded children (Wing & Gould, 1979) that the administrative category of mental retardation includes a substantial minority of people with severe impairment of two-way social interaction. Such social impairment occurred in 38% of the adult population and was very significantly associated with abnormalities of communication and imaginative activities. Muteness, repetitive stereotyped behaviour, including repetitive speech, and a range of behaviour problems also occurred more frequently in the socially impaired group. Two methods of sub-classifying the socially impaired were compared. Classification based on the severity of social impairment gave more statistically significant associations with behavioural and psychological variables than did a method based on the presence or absence of typical autism. The implications of these findings and their relevance for management and planning of services for the mentally retarded were briefly discussed.