Retarded children and their siblings.

One hundred and eighty-three retarded children and their nearest-in-age siblings were investigated. Ninety-five of the retarded children had Down's syndrome and 88 were retarded for other reasons. Interviews with the parents were carried out at home. Questionnaires on behaviour and educational attainment were completed for the retarded child, the sibling and a classroom control for the sibling. The retarded children had more behaviour problems than their siblings, as expected. The behaviour problems in the sibling were more often found if the retarded child had much-disturbed behaviour, especially when the retarded child had Down's syndrome. The siblings in the non-Down's group had more reading problems and more behaviour disturbance in school than either the controls or the siblings of Down's syndrome group.