Intellectual disability (
ID), also called
intellectual development disorder (
IDD) or
general learning disability, and formerly known as
mental retardation (
MR), is a generalized
neurodevelopmental disorder characterized by significantly impaired
intellectual and
adaptive functioning. It is defined by an
IQ score below 70 in addition to deficits in two or more
adaptive behaviors that affect everyday, general living. Once focused almost entirely on
cognition, the definition now includes both a component relating to mental functioning and one relating to individuals' functional skills in their environments. As a result of this focus on the person's abilities in practice, a person with an unusually low IQ may not be considered intellectually disabled. Intellectual disability is subdivided into
syndromic intellectual disability, in which intellectual deficits associated with other medical and behavioral
signs and symptoms are present, and
non-syndromic intellectual disability, in which intellectual deficits appear without other abnormalities.
Down syndrome and
fragile X syndrome are examples of syndromic intellectual disabilities.