This paper focuses on general social functioning in two groups of young men, one with autism and one with developmental receptive language disorders, who were first assessed at the ages of 7–8 years. At that time, although matched for nonverbal IQ (mean 92–93) and expressive language, the Language group showed significantly fewer social and behavioural problems. At follow-up, when aged on average, 23 to 24 years, the Autism group continued to show significantly more impairments in terms of stereotyped behaviour patterns, social relationships, jobs, and independence. However, problems in all these areas were also common in the Language group. Many still lived with their parents, few had close friends or permanent jobs, and ratings of social interaction indicated abnormalities in a number of different areas. On a composite measure of social competence only 10% of the Language group was assessed as having severe social difficulties compared to 74% of the Autism group. Nevertheless, 65% were rated as having moderate social problems and only 25% were rated as being of near/normal social functioning. Two individuals in the Language group, but none in the Autism group, had also developed a florid paranoid psychosis in late adolescence.

As in the follow-up of cognitive and linguistic functioning (see Mawhood et al., 2000, this volume, pp. 547–559), discriminant function analysis, which had clearly distinguished between the groups as children, now showed much greater overlap between them. Regression analysis indicated that although early language ability appeared to be related to outcome in the Autism group, there was little association between any measures of childhood functioning and prognosis in the Language group. Theoretically, these findings have implications for our understanding of the nature of autism and other pervasive language disorders, and of the relationship between them. Practically, they demonstrate the very persistent problems experienced by individuals with developmental language disorders, and their need for much greater help and support than is presently available.