The environment and mental retardation

A wide range of environmental affect intelligence and mental retardation. B iological risk factors for mental retardation include malnutrition; exposur e to toxins such as lead, alcohol, and PCBs, and being born at LBW. Social influences from homes, schools, and cultures are related to intelligence an d mental retardation although the direction of Effect is difficult to deter mine. Randomized early intervention studies with children in poverty provid e the best data showing that increased intelligence and adaptive behavior i s possible, although significant and sustained effects only result from int ensive services of long-term duration.