Learning disability

Learning disability


As with many other areas of psychiatry, the terminology used to describe what ICD10 classifies as mental retardation has changed regularly, to reflect changing philosophies of care and in an attempt to reduce stigma. The term ‘Learning disability’ is generally used in the UK and so is the one we have adopted in this book. An alternative term still used occasionally is mental handicap.


In learning disability there is impaired intellectual and social functioning that is apparent from early childhood. Intelligence is a broad concept that includes the ability to reason, comprehend and make judgements. It is measured with standardised tests such as the Wechsler Intelligence Scale, which has both performance and verbal sub-scales that can be reported separately or combined to produce a single IQ (intelligence quotient) score. An IQ of 70 and over is considered to be normal. Some 2–3% of the population have an IQ below 70, although half of these have a reasonable level of social functioning and can live independently without extra support. About 0.4% of adolescents have an IQ of less than 50.




Classification


Learning disability is classified as mild (IQ 50–69), moderate (IQ 35–49), severe (IQ 20–34) or profound (IQ under 20). The division into these four groups is fairly arbitrary and there is a great deal of overlap between them. The spectrum of disability for the key areas of language skills, self care, mobility, academic achievement and ability to work are shown in Table 1.



Table 1 Intellectual and social functioning in learning disability

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Aetiology


The cause of mild learning disability is unknown in about half of cases. Many of these simply represent the lower end of the normal distribution of intelligence. With increasing severity of learning disability, the likelihood of finding a cause increases, with at least 80% of severe cases having some evidence of organic brain damage or disease. Some of the aetiological factors are listed in Figure 1.


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Fig. 1 Aetiology of learning disability.


It is clear that social factors also play a role in causing learning disability. It has been estimated that up to 5% of cases are due to child abuse, with many being a consequence of brain damage, occurring as a direct result of physical assaults, usually by the parents. Other forms of abuse also appear to have an impact on intellectual performance. Emotional abuse by cruel and neglectful parents who fail to provide a stimulating and nurturing environment for their child results in impaired psychological and physical development. Institutional care can have a similar effect.


Two of the more common clinical syndromes that cause learning disability are described below.



Down’s syndrome


Down’s syndrome occurs in about 0.2% of all births and 1% of children born to women over 40 years. It is caused by a chromosomal abnormality, trisomy 21, in which there is an extra chromosome 21. People with Down’s syndrome have a characteristic facial appearance (Fig. 2). Congenital cardiac abnormalities are found in 40%. Nearly all have moderate or severe learning disability. It used to be thought that Down’s syndrome was associated with a particularly compliant and cheerful personality, but this is no longer considered to be the case and it is possible that these characteristics were due to the style of institutional care provided. In fact, children with Down’s syndrome have more behavioural problems than children of normal intelligence, although generally less than others with a comparable IQ.


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Fig. 2 Features of Down’s syndrome.

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Jul 12, 2016 | Posted by in PSYCHIATRY | Comments Off on Learning disability

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