Types of Mental Retardation

“We as a Nation have long neglected the mentally ill and the mentally retarded. This neglect must end, if our Nation is to live up to its own standards of compassion and dignity and achieve the maximum use of its manpower.” – John F. Kennedy

Toddler Girl Sitting On Floor

The term ‘mental retardation’, was once used for describing seemingly odd people who were comparatively much slower at learning and carrying out daily tasks. Fortunately, today mental retardation is universally referred to as ‘intellectual disability’. According to American Association of Intellectual and Developmental Disabilities (AAIDD), intellectual disability is defined as “a disability characterized by significant limitations in both intellectual functioning and in adaptive behavior, which covers many everyday social and practical skills. This disability originates before the age of 18.” Genetic irregularities, early childhood problems, birth problems, pregnancy complications, etc., are some of the major causes of mental retardation. In this PsycholoGenie article we discuss the four levels/types of intellectual disability, which are determined after assessing the individual’s IQ, adaptive behavior such as conceptual skills (reading and writing), social skills (responsibility and self-esteem), and practical skills (self-care). The individual’s health may be tested for identifying any visual, auditory, orthopedic, and congenital abnormalities.

According the Medilexicon’s medical dictionary, mental retardation is the “subaverage general intellectual functioning that originates during the developmental period and is associated with impairment in adaptive behavior. The American Association on Mental Deficiency lists eight medical classifications and five psychological classifications; the latter five replace the three former classifications of moron, imbecile, and idiot. Mental retardation classification requires assignment of an index for performance relative to a person’s peers on two interrelated criteria: measured intelligence (IQ) and overall socioadaptive behavior (a judgmental rating of the person’s relative level of performance in school, at work, at home, and in the community). In general an IQ of 70 or less indicates mental retardation (mild = 50/55-70; moderate = 35/40-50/55; severe = 20/25-35/40; profound = below 20/25); an IQ of 70-85 signifies borderline intellectual functioning.”
Criteria for Determining Intellectual Disability
The individuals being assessed for intellectual disabilities must meet three basic criteria:

  • Show significant limitations in their intellectual functioning
  • Significant limitations in adaptive behavior
  • The onset of these significant limitations began before the age of 18.

Levels of Intellectual Disability
Categories or levels of intellectual disability are defined by assessing IQ scores of the individual. Based on the scores achieved, the level of mental retardation is determined. These levels also help in determining the type of support needed to help the individual cope. Following are the four levels of intellectual disability:

1. Mild

The following criteria must be met in order to diagnose an individual with mild intellectual disabilities:

  • Has an IQ between 50-70
  • Does not have any unusual physical signs
  • Takes slightly longer than normally expected in all aspects, such as takes longer to learn how to talk and communicate
  • Is capable of independent self-care
  • Is capable of learning practical skills
  • Knowledge of reading, writing, and math skills are limited to grade 3-6
  • Is capable of social interactions, is communicative, and conforms socially
  • Is capable of functioning in society
2. Moderate

The following criteria must be met in order to diagnose an individual with moderate intellectual disabilities:

  • Has an IQ between 35-49
  • Could have unusual physical signs
  • Is noticeably delayed in all aspects, such as speech, reading, and writing
  • Is capable of grasping simple communicative skills
  • Is capable of learning basic health, self-care, and safety skills
  • Can perform simple activities and supervised tasks
  • Is capable of traveling unaccompanied to familiar places
3. Severe

The following criteria must be met in order to diagnose an individual with severe intellectual disabilities:

  • Has an IQ between 20-34
  • Is noticeably motor impaired
  • Is significantly delayed in certain areas such as walking
  • Has little or absolutely no communicative skills, but has some ability to understand speech and respond to a small extent
  • Is capable of being taught daily and repetitive activities
  • May be taught to carry out simple self-care activities
  • Requires supervision and directions in social settings
4. Profound

The following criteria must be met in order to diagnose an individual with profound intellectual disabilities:

  • Has an IQ lesser than 20
  • Is significantly slower and delayed in all aspects
  • There is presence of congenital abnormalities
  • Needs to be supervised closely
  • Requires the care of an attendant
  • May respond positively to physical and social activities, if made to practice on a regular basis
  • Is incapable of performing self-care activities

Around three percent of the American population suffers from some level of intellectual disability. Such individuals can lead a better life with proper support, care, and guidance from health care providers and family.