Mental retardation is diagnosed if I.Q. (Intelligence quotient) is less than :

The IQ cut off point for diagnosis of mental retardation is 70. Grades of mental retardation based on IQ levels are: Mild mental retardationIQ 50-55 and 70Moderate35-40 and 50-55Severe20-25 and 35-40Profoundbelow 20 or 25Diagnostic criteria for mental retardation includes:An IQ of approximately 70 or below on an individually administered IQ test.Impairment in adaptive functioning in at least two of the following areas such as communication, self care, home living, social /interpersonal skills, functional academic skills, work, leisure, health and safety.Onset should be before 18 years.Ref: DSM-IV-TR Guidebook By Allen Frances, page 373, Abnormal Psychology: An Integrated Approach: An Integrative Approach By David H. Barlow, page 519.