Mental Retardation


A disability characterized by significant limitations both in intellectual functioning and in adaptive behavior as expressed in conceptual, social and practical adaptive skills. This disability originates before age 18. (American Association on Mental Retardation-AAMR; now called the American Association of Intellectual and Developmental Disorders).

An impairment that presents itself in substantial deficiencies in both intellectual functioning and adaptive behaviour, as reflected in conceptual, social, and functional adaptive skills. This condition begins before the age of 18 years. (AAMR; now known as the American Association of Intellectual and Cognitive Disorders)

IDEA definition of mental retardation:

Significantly sub-average general intellectual functioning, existing concurrently with deficits in adaptive behavior and manifested during the developmental period that adversely affects a child’s educational performance.

Mental Retardation is a generalized disorder, characterized by significantly impaired cognitive functioning and deficits in two or more adaptive behaviors that appear before adulthood. It has historically been defined as an Intelligence Quotient score under 70. 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 environment. As a result, a person with a below-average intelligence quotient (BAIQ) may not be considered mentally retarded.

Mental Retardation – means subaverage general intellectual functioning associated with mal-adaptive behavior, occurring in the developmental period. Mental retardation is divisible into the following four categories

  • Profound retardation IQ under 20 
  • Mild retardation IQ – 50 – 70
  • Moderate retardation IQ – 35 – 49
  • Severe retardation IQ – 20 – 34