Webum > Kids and Teens > Health > Conditions and Diseases > Mental Retardation Down Syndrome@ Fact Sheet: Mental Retardation Definition, causes, diagnosis, and information from the National Information Center for Children and Youth with Disabilities. Mental Retardation Provides a definition, suspected causes, and what life is like for someone who is mentally retarded. Help build the biggest human edited directory on the internet Add your website - Open Directory Project - Become an editor