Mental retardation (also called mental handicap, mental impairment and severe mental impairment) is a term for a pattern of persistently slow learning of basic motor and language skills ("milestones") during childhood, and a significantly below-normal global intellectual capacity as an adult. One common criterion for diagnosis of what used to be called mental retardation is a tested intelligence quotient (IQ) below 70.
There are three criteria before a person is considered to have a developmental disability: an IQ below 70, significant limitations in two or more areas of adaptive behavior (i.e., ability to function at age level in an ordinary environment), and evidence that the limitations became apparent in childhood. Down syndrome, fetal alcohol syndrome and fragile X are the three most common inborn causes.
By most definitions, it is more accurately considered a disability rather than a disease. It can be distinguished in many ways from mental illness, such as schizophrenia or depression.
There is no "cure" for an established disability, though with appropriate support and teaching most individuals can learn to do many things.
