Developing at a far slower rate than the child's peers.
Some disorders have similar or even the same symptoms.
None Detailed Causes Mental retardation can be caused by any condition which impairs development of the brain before birth, during birth, or in the childhood years. Several hundred causes have been discovered, but in about one-third of the people affected, the cause remains unknown. The three major known causes of mental retardation are the genetic conditions of Down Syndrome , Fragile X, and Fetal Alcohol Syndrome , the result of alcohol consumption during pregnancy . The primary goal of treatment is to develop the person's potential to the fullest. Special education and training may begin as early as infancy.