<prompt> Severe mental retardation means IQ in the range of50-7035-5020-3520  <response>: ICD-10 Codes for Mental Retardation F70 Mild mental retardation IQ 50-69 F71 Moderate mental retardation IQ 35-49 F72 Severe mental retardation IQ 20-34 F73 Profound mental retardation IQ 20 Reference: Page No .3450 chap. 37 Intellectual Disability Kaplan Sadocks Comprehensive Textbook of Psychiatry, 9th Edition 