Mental Retardation

The essential features of Mental Retardation is significantly subaverage general intellectual that is characterized by the following:

• Significantly subaverage intellectual functioning: an IQ of approximately 70 or below on an individually administered IQ test (for infants, a clinical judgment of significantly subaverage intellectual functioning).

• Concurrent deficits or impairments in present adaptive functioning (i.e., the person's effectiveness in meeting the standards expected for his or her age by his or her cultural group) in at least two of the following areas: communication, self-care, home living, social/interpersonal skills, use of community resources, self-direction, functional academic skills, work, leisure, health, and safety.

• The onset is before age 18 years.

Mild Mental Retardation (IQ 50-70)

Mild Mental Retardation is roughly equivalent to what used to be referred to as the educational category of "educable." This group constitutes the largest segment (about 85%) of those with the disorder. With appropriate supports, individuals with Mild Mental Retardation can usually live successfully in the community, either independently or in supervised settings.

Moderate Mental Retardation (IQ 35-55)

Moderate Mental Retardation is roughly equivalent to what used to be referred to as the educational category of "trainable." This outdated term should not be used because it wrongly implies that people with Moderate Mental Retardation cannot benefit from educational programs. This group constitutes about 10% of the entire population of people with Mental Retardation. Most of the individuals with this level of Mental Retardation acquire communication skills during early childhood years.

They profit from vocational training and, with moderate supervision, can attend to their personal care. In their adult years, the majority are able to perform unskilled or semiskilled work under supervision in sheltered workshops or in the general workforce.

Severe Mental Retardation (IQ 20-40)

The group with Severe Mental Retardation constitutes 3%–4% of individuals with Mental Retardation. They profit to only a limited extent from instruction in pre-academic subjects, such as familiarity with the alphabet and simple counting, but can master skills such as learning sight reading of some "survival" words. In their adult years, they may be able to perform simple tasks in closely supervised settings. Most adapt well to life in the community, in group homes or with their families, unless they have an associated handicap that requires specialized nursing or other care.

Profound Mental Retardation (IQ below 20-25)

The group with Profound Mental Retardation constitutes approximately 1%–2% of people with Mental Retardation. Most individuals with this diagnosis have an identified neurological condition that accounts for their Mental Retardation. During the early childhood years, they display considerable impairments in sensorimotor functioning. Some can perform simple tasks in closely supervised and sheltered settings.

Borderline Intellectual Functioning (IQ 71-84)

This group has an IQ within 71-84. The diagnosis of this disorder is usually difficult when the coexistence of certain mental disorders (e.g., Schizophrenia) is involved. An IQ score may involve a measurement error of approximately 5 points, depending on the testing instrument. Thus, it is possible to diagnose Mental Retardation in individuals with IQ scores between 71 and 75 if they have significant deficits in adaptive behavior that meet the criteria for Mental Retardation. Differentiating Mild Mental Retardation from Borderline Intellectual Functioning requires careful consideration of all available information.

Diagnostic criteria summarized from:

American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders, fourth edition. Washington, DC: American Psychiatric Association.