Is mental retardation the same as mental illness?

Answer

No, not by a long shot. Mental retardation involves an extra chromosome and is present at birth. Or, a severe illness (like lengthy high fever) can cause some mental defects in children.
Mental illness can be created by stress, heredity, genetic predisposition, or any of many other factors. It is not predictable or screenable. It can also vary from mild to severe with huge variances in presentation. It can also appear later in life to people with perfectly normal IQ's and reasoning skills.

Mental retardation does not always involve an extra chromosome. It may be caused by genetics, problems during pregnancy, birth problems, problems that may occur after birth, socio-economic deprivation and other accidental causes. It occurs before the age of 18 and may be present at birth.

If an individual has an IQ that is generally 70 or below with co-occuring deficits in major life areas such as communication, mobility, learning, self direction, etc., mental retardation may be diagnosed.