Mental Retardation

DEFINITION
The American Association on Mental Retardation gives the following definition, “Mental Retardation is a disability, characterized by significant limitations in intellectual functioning and adaptive behavior as expressed in conceptual, social and practical adaptive skills.”

According to the Diagnostics and Statistical Manual IV TR (text revision), this disorder is characterized by significantly sub average intellectual functioning (an IQ of approximately 70 or below) with onset before age 18 years and concurrent deficits or impairments in adaptive functioning.

DIAGNOSTIC FEATURES
The essential feature o f Mental Retardation is significantly subaverage general intellectual functioning (Criterion A) that is accompanied by significant limitations in adaptive functioning in at least two of the following skill areas: communication, self-care, home living, social/interpersonal skills, use of community resources, self-direction, functional academic skills, work, leisure, health, and safety (Criterion B). The onset must occur before age 18 years (Criterion C). Mental Retardation has many different etiologies and may be seen as a final common pathway of various pathological processes that affect the functioning of the central nervous system.
General intellectual functioning is defined by the intelligence quotient (IQ or IQ equivalent) obtained by assessment with one or more of the standardized, individually administered intelligence tests (e.g., Wechsler Intelligence Scales for Children, 3rd Edition; Stanford-Binet, 4th Edition).

Significantly subaverage intellectual functioning is defined as an IQ of about 70 or below (approximately 2 standard deviations below the mean).

Impairments in adaptive functioning, rather than a low IQ, are usually the presenting symptoms in individuals with Mental Retardation. Adaptive functioning refers to how effectively individuals cope with common life demands and how well they meet the standards of personal independence expected of someone in their particular age group, Sociocultural background, and community setting. Several scales have also been designed to measure adaptive functioning or behavior (e.g., the Vineland Adaptive Behavior Scales and the American Association on Mental Retardation Adaptive Behavior Scale).

DEGREES OF SEVERITY OF MENTAL RETARDATION
Four degrees of severity can be specified, reflecting the level of intellectual impairment: Mild, Moderate, Severe, and Profound.

Mild Mental Retardation: IQ level 5o-55 to approximately 70

Moderate Retardation: IQ level 35-40 to 50-55

Severe Mental Retardation: IQ level 20--25 to 35-40

Profound Mental Retardation: IQ level below 20 or 25

MILD MENTAL RETARDATION
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. As a group, people with this level of Mental Retardation typically develop social and communication skills during the preschool years (ages O-5 years), have minimal impairment in sensorimotor areas, and often are not distinguishable from children without Mental Retardation until a later age. By their late teens, they can acquire academic skills up to approximately the sixth-grade level. During their adult years, they usually achieve social and vocational skills adequate for minimum self-support, but may need supervision, guidance, and assistance, especially when under unusual social or economic stress. With appropriate supports, individuals with Mild Mental Retardation can usually live successfully in the community, either independently or in supervised settings.

MODERATE MENTAL RETARDATION
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. They can also benefit from training in social and occupational skills but are unlikely to progress beyond the second-grade level in academic subjects. They may learn to travel independently in familiar places. During adolescence, their difficulties in recognizing social conventions may interfere with peer relationships. In their adult years, the majority are able to perforn1 unskilled or semiskilled work under supervision in sheltered workshops or in the general workforce. They adapt well to life in the community, usually in supervised settings.

SEVERE MENTAL RETARDATION
The group with Severe Mental Retardation constitutes 3%--4% of individuals with Mental Retardation. During the early childhood years, they acquire little or no communicative speech. During the school-age period, they may learn to talk and can be trained in elementary self-care skills. 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
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. Optimal development may occur in a highly structured environment with constant aid and supervision and an individualized relationship with a caregiver. Motor development and self-care and communication skills may improve if appropriate training is provided. Some can perform simple tasks in closely supervised and sheltered settings.

CAUSES OF MENTAL RETARDATION
The causes of mental retardation can be divided into biomedical, social, behavior and educational risk factors that interact during the life of an individual and/or across generations from parent to child.

1. Biomedical factors are related to biological processes, such as genetic disorders or nutrition.

2. Social factors are related to social and family interaction, such as child stimulation and adult responsiveness.

3. Behavioral factors are related to harmful behaviors, such as maternal substance abuse.

4. Educational factors are related to the availability of family and educational supports that promote mental development and increases in adaptive skills.

5. Factors present during one generation can influence the outcomes of the next generation. By understanding inter-generational causes, appropriate support can be used to prevent and reverse the effects of risk factors.