EPIDEMIOLOGY OF MENTAL-RETARDATION IN CHILDREN

Mental retardation (MR) in children is a heterogeneous group of disord ers with varied causes. This article describes well-known causes of MR and epidemiologically established risk factors. Approximately 43-70% of children with severe MR (i.e., intelligence quotient [IQ] of <50) h ave a known cause of MR, compared with 20-24% of those with mild MR (I Q of 50-70). Investigators will need to continue refining research met hods to define homogeneous groups for the further identification of ca uses of MR in children. Discovery of additional genetic factors and th eir causal link to MR will continue to diminish the proportion of MR w ith unknown causes. areas of NIR research that will be particularly ch allenging are (1) the relationship between socioeconomic factors and o ther risk factors or causes of MR and (2) how much of the variation in prevalence of MR associated with prenatal or perinatal biologic insul ts is due to differences in the quality of intervening care and the po stnatal environment. (C) 1998 Wiley-iiss, Inc.