BackgroundThe clinical pictures of autistic spectrum disorders include features described in catatonia.AimsTo examine the severe exacerbation of the catatonic features of autistic disorders in adolescence or early adult life, which occurs in some individuals.MethodA semi-structured interview schedule was used to collect information from parents or other care-givers concerning 506 referrals to a specialist clinic for autistic spectrum disorders. Individuals with severe exacerbation of catatonic features were compared with a same-age group of referrals without this type of deterioration in skills and behaviour.ResultsSeventeen per cent of referrals aged 15 or over had severe exacerbation of catatonic features. They were significantly more likely than the comparison group to have had, before the onset of the change in behaviour, impaired language and passivity in social interaction.ConclusionsCatatonia is a later complication of autistic spectrum disorders, which adds considerably to the burden of caring. More research is needed to identify causes, neuropathology, and early signs of vulnerability.