Children diagnosed with mental retardation have an IQ below 70 (there are tests to determine a child’s IQ score) and the condition is expressed before age 18. These persons will develop more lowly in adaptive behavioral areas than others with normal intelligence.
Factors of Mental Retardation. Mental retardation is below average intelligence and abilities which are present before the age of 18. This is determined by an IQ below 70 - 75, significantly limited in two or more skill areas such as school, work, social, and communication, and this condition has to have been present since childhood (18 years of age or younger).