Effects of chronic illness on intellectual development. A comparison of normal children with those treated for childhood leukaemia and solid tumours.

40 children who had been treated for acute lymphoblastic leukaemia by irradiation to the central nervous system and by chemotherapy were assessed, using general psychological measures. These children were compared with a group of normal children of similar ages and backgrounds, and with a group of 16 patients treated for solid tumours. The group of 16 patients with solid tumours was also compared with a normal control group and there were no differences between the scores for IQ, reading, memory, and learning. Children with leukaemia had lower scores then normal children for all these tasks. In young leukaemic children (those diagnosed when aged under 5 years) differences were significantly greater compared with controls. There were no effects of age at diagnosis on the scores made by children with solid tumours compared with normal children. These results implicate the role of central nervous system irradiation in reducing intellectual development in children, especially in young children, treated for leukaemia.