Mental Retardation is defined as below-average general intellectual function with associated deficits in adaptive behavior that occurs before age 18. It is characterized by significantly sub-average intellectual functioning, existing concurrently with related limitations in two or more of the following applicable adaptable skill areas: communication, self-care, home living, social skills, community use, self direction, health and safety, functional academics, leisure and work. Mental retardation has been classified by the degree or level of intellectual impairment, as measured by an IQ test. The most widely used classification method consists of four levels of mental retardation according to the range of IQ scores shown in the table below.

PSYCHOLOGICAL CLASSIFICATION

• Level I.Q.
• Mild retardation 50 to 70
• Moderate retardation 35 to 49
• Severe retardation 20 to 34
• Profound retardation Below 20

EDUCATIONAL CLASSIFICATION

• Level I.Q.
• Educable 50 to 75
• Trainable 25 to 50
• Custodial 0 to 25 (Totally dependent)

Intelligent Quotient ( I.Q. ) = Mental Age / Chronological Age x 100

There are numerous causes of mental retardation, but a specificity is determined in only 25% of the cases. Failure to adapt normallyand grow intellectually may become apparent early in life or, in the case of mild retardation, not become recognizable until school age or later. An assessment of age-appropriate adaptive behaviors can be made by the use of developmental screening tests. The failure to achieve developmental milestones is suggestive of mental retardation. A family may suspect mental retardation if motor skills, language skills, and self-help skills do not seem to be developing in a child or are developing at a far slower rate than the child’s peers. The degree of impairment from mental retardation has a wide range from profoundly impaired (5%) to mild or borderline retardation (80- 90%). Less emphasis is now placed on degree of retardation and more on the amount of intervention and care required for daily life.

Characteristics and Symptoms Mental retardation comprises five general categories: borderline, mild, moderate, severe and profound. Categories are based on scores obtained through use of age- standardized tests of cognitive ability. Click here to view the table Mental retardation may occur as part of a syndrome or broader disorder but is most commonly an isolated finding. Typical symptoms of mental retardation are:

• Failure to meet intellectual developmental markers
• Persistence of infantile behavior
• Lack of curiosity
• Decreased learning ability
• Inability to meet educational demands of school

Deviations in normal adaptive behaviors depend on the severity of the condition. Mild retardation may be associated with a lack of curiosity and quiet behavior. Severe mental retardation is associated with infantile behavior throughout life.