Behavioural symptoms and autistic psychosis in the mentally retarded adult.

302 mentally retarded (MR) adults, representative of the total Danish MR population, were examined with regard to behavioural symptoms and psychiatric disorder. Deviant behaviour was found in 123 (41%) and was correlated to origin and degree of retardation, epilepsy and place of living. The distribution of the symptoms strongly indicates that organic brain damage is the major etiological cause. By grouping behavioural symptoms on three axes: A: social withdrawal (27%), B: abnormal bodily movements and sensory stimulation (22%) and C: conduct behaviour (17%), different patterns of abnormal behaviour were demonstrated. Behavioural symptoms occurred in 74 (87%) of 85 persons given present state psychiatric diagnoses. Behavioural symptoms are prominent in the group of autistic psychosis (childhood autism), which is classified by the triad of 1) autism, 2) abnormal language, and 3) stereotypic behaviour. This diagnosis was established in 23 (7.6%), and differences in psychopathology are basically determined by degree of intellectual resources, with the subgroup of Kanner's early childhood autism constituting the upper level.