Management of Mental Sub-Normality Definition: Mental sub-normality (also referred to as intellectual disability) is a developmental condition characterized by significant limitations in intellectual functioning (IQ below 70) and adaptive behavior (e.g., daily living skills, communication, and social skills), with onset before the age of 18. Goals of Management: Levels of Mental Sub-Normality: Category IQ Range Characteristics Mild 50–69 Can achieve basic academic skills, may live independently. Moderate 35–49 Limited academic