The incidence of congenital mental handicaps in New Zealand

Abstract

This study attempted to ascertain the incidence of congenital mental handicaps in New Zealand and to discuss this incidence in terms of cause, degree of retardation and differences between the sexes. It is hoped that the information will be useful as baseline data for subsequent studies and perhaps be of epidemiological use in prevention, intervention and in the planning of services. A questionnaire was developed and sent to all facilities in New Zealand at which it was likely that surviving children, born in 1973 and 1974 with mental handicaps, would be enrolled. The response rate was almost 95 percent. Incidence rates were calculated for children with congenital mental handicaps surviving to at least ten years of age. Rates were determined for ascribed cause, by sex and by degree of handicap. A number of handicaps were classified as having an unknown cause and that this may mean that the actual incidence of congenital mental handicaps is higher than that expressed in this study. The causes of congenital mental handicaps found to have the highest incidence were Down's syndrome, Microcephaly, Hydrocephaly, Cerebral Palsy, Familial/Cultural Causes and Genetic/Chromosomal anomalies.