Mental retardation

Mental retardation (also called mental handicap and, as defined by the UK Mental Health Act (1983), mental impairment and severe mental impairment) is a term for a pattern of persistently slow learning of basic motor and language skills ("milestones") during childhood, and a significantly below-normal global intellectual capacity as an adult. One common criterion for diagnosis of what used to be called mental retardation is a tested intelligence quotient (IQ) below 70.

Signs

There are many signs. For example, children with disabilities may:

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• sit up, crawl, or walk later than other children;
• learn to talk later, or have trouble speaking,
• find it hard to remember things,
• not understand how to pay for things,
• have trouble understanding social rules,
• have trouble seeing the consequences of their actions,
• have trouble solving problems, and/or
• have trouble thinking logically.

About 87 percent of people with a developmental disability will only be a little slower than average in learning new information and skills. In early childhood, mild disability (IQ 60-70) may not be obvious, and may not be diagnosed until they begin school. Even when poor academic performance is recognized, it may take expert assessment to distinguish mild mental disability from learning disability or behavior problems. As they become adults, many people can live independently and may be considered by others in their community as "slow" rather than "retarded".

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Moderate disability (IQ 50-60) is nearly always obvious within the first years of life. These people will encounter difficulty in school, at home, and in the community. In many cases they will need to join specially separated classes, but they can still progress to become functioning members of society.

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The remaining 13 percent of individuals with mental disability score below 50 on IQ tests. A person with a more severe disability will need more intensive support and supervision his or her entire life.

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Nevertheless, every child is able to learn, develop, and grow to some extent. The capacity to experience joy and human relationships is not IQ-dependent.

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Diagnosis

It is formally diagnosed by professional assessment of intelligence and adaptive behavior.

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Intelligence is the ability of a person to learn, think, solve problems, and make sense of the world (called IQ or intellectual functioning). Intellectual functioning is usually measured by a test called an IQ test. The average score is 100. People scoring below 75 are often ? but not always ? mentally disabled. Since factors other than mental ability (depression, anxiety, lack of adequate effort, etc.) can yield low IQ scores, it is important for the evaluator to rule them out prior to concluding that measured intelligence is "significantly below average".

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Adaptive behavior, or adaptive functioning refers to the skills needed to live independently (or at the minimally acceptable level for age). To assess adaptive behavior, professionals compare the functional abilities of a child to those of other children of similar age. To measure adaptive behavior, professionals use instruments that are actually structured interviews, with which they systematically elicit information about the person's functioning in the community from someone that knows them well. There are many adaptive behavior scales, and accurate assessment of the quality of someone's adaptive behavior requires clinical judgement as well. Certain skills are important to adaptive behavior, such as:

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• daily living skills, such as getting dressed, going to the bathroom, and feeding one's self;
• communication skills, such as understanding what is said and being able to answer;
• social skills with peers, family members, adults, and others.

Ranges of IQ

The following ranges, based on the Wechsler Adult Intelligence Scale (WAIS), are in standard use today:

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ClassIQ

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Profound mental retardationbelow 20

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Severe mental retardation20-34

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Moderate mental retardation35-49

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Mild mental retardation50-69

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Borderline deficiency70-79

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