Epidemiology of learning disability
Clinical features of learning disability
Physical disorders among people with learning disability
Psychiatric disorders among people with learning disability
Other clinical aspects of learning disability
Aetiology of learning disability
Assessment and classification of people with learning disability
The care of people with learning disability
Treatment of psychiatric disorder and behavioural problems
Ethical and legal issues in learning disability
This chapter is concerned with a general outline of the features, epidemiology, and aetiology of learning disability (mental retardation), the organization of services and, more specifically, with the psychiatric disorders that affect these people. Many of the psychiatric problems of children with learning disability are similar to those of children of normal intelligence; an account of these problems is given in Chapter 22 on child psychiatry.
Over the years, several terms have been applied to people with intellectual impairment from early life. In the nineteenth and early twentieth centuries, the word ‘idiot’ was used for people with severe intellectual impairment, and ‘imbecile’ for those with moderate impairment. The special study and care of such people was known as the field of mental deficiency. When these words came to carry stigma, they were replaced by the terms mental subnormalityand mental retardation. The term mental handicap has also been widely used, but now the term learning disability is generally preferred in the UK (and is used in this chapter). However, the term mental retardation is still used in ICD-10 and DSM-IV, and is employed in many countries. Moreover, in the USA the term learning disability is generally applied to dyslexia and similar forms of specific disability, rather than to mental retardation. For this reason the alternative term intellectual disability is gaining acceptance.
The development of ideas about learning disability
A fundamental distinction has to be made between general intellectual impairment starting in early childhood (learning disability or mental retardation) and intellectual impairment developing later in life (dementia). In 1845, Esquirol made this distinction when he wrote:
Idiocy is not a disease, but a condition in which the intellectual faculties are never manifested, or have never been developed sufficiently to enable the idiot to acquire such an amount of knowledge as persons of his own age and placed in similar circumstances with himself are capable of receiving.
(Esquirol, 1845, pp. 446–7)
Early in the twentieth century, Binet’s tests of intelligence provided quantitative criteria for ascertaining the condition. These tests also made it possible to identify lesser degrees of the condition that might not be obvious otherwise (Binet and Simon, 1905). Unfortunately, it was widely assumed at the time that people with such lesser degrees of intellectual impairment were socially incompetent and required institutional care.
Similar views were reflected in the legislation of the time. For example, in England and Wales the Idiots Act of 1886 made a simple distinction between idiocy (more severe) and imbecility (less severe). In 1913, the Mental Deficiency Act added a third category for people who ‘from an early age display some permanent mental defect coupled with strong vicious or criminal propensities in which punishment has had little or no effect.’ As a result of this legislation, people of normal or near normal intelligence were admitted to hospital for long periods simply because their behaviour offended against the values of society. Although some of these people had committed crimes, others had not—for example, girls whose illegitimate pregnancies were interpreted as a sign of the ‘criminal’ propensities mentioned in the Act.
Although in the past the use of social criteria clearly led to abuse, it is unsatisfactory to define mental retardation in terms of intelligence alone. Social criteria must be included, since a distinction must be made between people who can lead a normal or near-normal life and those who cannot. DSM-IV defines mental retardation as a ‘significantly sub-average general intellectual functioning, 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 used for community resources, self-direction, functional academic skills, work, leisure, health and safety’, and having an onset before the age of 18 years. Having defined the disorder in this way, it is subdivided by level of intelligence. In both ICD-10 and DSM-IV the subtypes are as follows: mild (IQ 50–70); moderate (IQ 35–49); severe (IQ 20–34); profound (IQ below 20). Acquired brain injury (ABI) is the term used to describe individuals who develop a learning disability after the age of 18 years (e.g. following a head injury).
The original World Health Organization (WHO) classification of impairment, disability, and handicap is useful when considering the problems of people with learning disability. (The WHO now employs a more positive terminology, with activity replacing ‘disability’, and participation replacing ‘handicap.’) The impairment is of the central nervous system, and the disability (or limitation of activity) is in learning and acquiring new skills. The extent to which impairment leads to disability (limits activity) depends, in part, on experiences in the family and at school, and on the correction of associated problems such as deafness. The final stage, namely handicap (or limited participation), depends on the degree of disability and on other factors such as the support that is provided.
Educationalists use other terms, and these differ between countries. In the UK, the term is special needs, whereas in the USA three groups are recognized—educable mentally retarded (EMR), trainable mentally retarded (TMR), and severely mentally retarded (SMR).
Epidemiology of learning disability
In 1929, in an important early survey, E. O. Lewis found that among schoolchildren in six areas of the UK the prevalence of mental retardation was 27 in 1000 children, and that of moderate and severe learning disability (IQ less than 50) was 3.7 in 1000. Subsequent studies have produced variable results, but a current estimate for the UK is 9–14 in 1000 children, and 3–8 in 1000 adults (Cooper and Smiley, 2009).
Variability in apparent prevalence rates is due partly to experimental factors such as methods of ascertainment and definition, but also reflects genuine differences in prevalence, and incidence, across time and place. In recent years, the incidence of severe learning disability has fallen substantially, because of the recognition of preventable prenatal and perinatal causes of learning disabilities. However, the prevalencehas not fallen, and in fact is expected to rise by over 10% by 2020. The preserved or increasing prevalence despite reduced incidence reflects two factors. First, people with learning disability, particularly those with Down’s syndrome, are living longer. This has also affected the age distribution of people with severe learning disability, so that the numbers of adults have increased. Secondly, improvements in maternal and neonatal care are resulting in a growing number of children with learning disabilities, especially those in the severe and profound categories, who have survived significant events such as extreme prematurity.
A further important point regarding the prevalence of learning disability was made by Tizard (1964), who drew attention to the distinction between ‘administrative’ prevalence and ‘true’ prevalence. He defined the former as ‘the numbers for whom services would be required in a community which made provision for all who needed them.’ (In practice, the term usually means the number with needs who are known to the service providers.) It is estimated that less than 50% of all such people require special provision. Administrative prevalence is higher in lower socio-economic groups and in childhood when more patients need services. It falls after the age of 16 years because there is continuing slow intellectual development and gradual social adjustment.
The epidemiology of psychiatric disorders in learning disability is covered later in the chapter.
Clinical features of learning disability
The most frequent manifestation of learning disability is uniformly low performance on all kinds of intellectual task, including learning, short-term memory, the use of concepts, and problem solving. Specific abnormalities may lead to particular difficulties. For example, lack of visuo-spatial skills may cause practical difficulties, such as inability to dress, or there may be disproportionate difficulties with language or social interaction, both of which are strongly associated with behaviour disorder. Among children with learning disability, the common behaviour problems of childhood tend to occur when they are older and more physically developed than children in the general population, and the problems last for longer. Such behaviour problems usually improve slowly as the child grows older, but may be replaced by problems that start in adulthood.
Learning disability is usually divided into three or four subtypes, which are defined by IQ (see Table 23.1). This classification is useful descriptively, and for understanding the epidemiology and aetiology of learning disability, as well as its management. The clinical features of the individual syndromes that cause learning disability are described later in the chapter.
Table 23.1 Features of mild, moderate, and severe/profound learning disability
Mild learning disability (IQ 50–70)
People with mild learning disability account for about 85% of those with learning disability. Usually their appearance is unremarkable and any sensory or motor deficits are slight. Most people in this group develop more or less normal language abilities and social behaviour during the preschool years, and their learning disability may never be formally identified. In adulthood, most people with mild learning disability can live independently in ordinary surroundings, although they may need help in coping with family responsibilities, housing, and employment, or when under unusual stress.
Moderate learning disability (IQ 35–49)
People in this group account for about 10% of those with learning disability. Many have better receptive than expressive language skills, which is a potent cause of frustration and behaviour problems. Speech is usually relatively simple, and is often better understood by people who know the patient well. Many make use of simplified signing systems such as Makaton sign language. Activities of daily living such as dressing, feeding, and attention to hygiene can be acquired over time, but other activities of daily living such as the use of money and road sense generally require support. Similarly, supported employment and residential provision are the rule.
Severe learning disability (IQ 20–34)
It is difficult to estimate IQ accurately when the score is below 34 because of the difficulty in administering the tests in a valid manner to individuals in this group. Estimates suggest that people with severe learning disability account for about 3–4% of the learning disabled. In the preschool years their development is usually greatly slowed. Eventually many of them can be helped to look after themselves under close supervision, and to communicate in a simple way—for example, by using objects of reference. As adults they can undertake simple tasks and engage in limited social activities, but they need supervision and a clear structure to their lives.
Profound learning disability (IQ below 20)
People in this group account for 1–2% of those with learning disability. Development across a range of domains tends to be around the level expected of a 12-month-old infant. Accordingly, people with profound learning disability are a vulnerable group who require considerable support and supervision, even for simple activities of daily living.
Physical disorders among people with learning disability
People with learning disabilities experience a greater variety and complexity of physical health problems than the rest of the population, but may not complain of feeling ill, nor be able to articulate their symptoms, and conditions may be noticed only because of changes in behaviour. Clinicians should be aware of the associations between certain learning disability syndromes and physical illness (e.g. Down’s syndrome; see p. 691), and that people with a learning disability are more likely to die prematurely (McGuigan et al., 1995). Learning disability also has an impact on physical health in ageing (Holland, 2000).
Sensory and motor disabilities and incontinence are the most important physical disorders in people with learning disability. People with severe learning disability (especially children) usually have one or often several of these problems. Only one-third are continent, ambulant, and without severe behaviour problems. Around 25% are highly dependent on other people. Among the people with mild learning disability, similar problems occur, but less frequently. Nevertheless, they are important because they determine whether special educational programmes are needed. Sensory disorders add an important additional obstacle to normal cognitive development. Motor disabilities include spasticity, ataxia, and athetosis. Ear infections and dental caries are common in this population.
Epilepsy is a frequent and clinically important problem in learning disability. Around 15–25% of people with learning disabilities have a history of epilepsy, compared with 5% in the general population. The prevalence increases with the severity of learning disabilities, with lifetime history of epilepsy estimated to be 7–15% in mild to moderate learning disability, 45–67% in severe learning disability, and up to 80% in profound learning disability. Epilepsy is more commonly associated with certain causes of learning disability, such as fragile X syndrome, tuberous sclerosis, Angelman syndrome, and Rett syndrome, while certain epilepsy syndromes, such as West’s syndrome and Lennox–Gastaut syndrome, are more common among people with learning disability. The proportion of epilepsy cases that are drug-resistant is also greater among people with learning disability. Of particular concern is the incidence of sudden unexplained death in epilepsy (SUDEP), which is estimated to be 1 in 295 per year in the learning-disabled population, compared with 1 in 1000 per year in epilepsy patients in the general population.
For a review of the aetiology, diagnosis, and treatment of epilepsy in learning disability, see Iivanainen (2009).
Psychiatric disorders among people with learning disability
In the past, psychiatric disorder among the learning disabled was often viewed as different from that seen in people of normal intelligence. One view was that people with learning disability did not develop emotional disorders. Another view was that they developed these disorders, but that the causes were biological rather than psychosocial. It is now generally agreed that people with learning disability experience psychiatric disturbances similar to those which affect the general population. However, the symptoms are sometimes modified by low intelligence, and may not be easily recognized or communicated. Therefore, when diagnosing psychiatric disorder among people with learning disability, more emphasis may have to be given to behaviour and less to reports of mental phenomena than is usually the case.
For reviews of psychiatric disorders in learning disability, see Tonge (2009) and Dosen (2009), and for a review of their clinical assessment, see Holland (2009). Here we outline their epidemiology and clinical characteristics. Their assessment and treatment are covered later in the chapter.
Epidemiology and features of psychiatric disorder in people with learning disability
Among people with learning disability, published rates of psychiatric disorder vary widely, because of similar difficulties with case ascertainment, detection, and definition. Early studies primarily had the selection bias of including mainly people from institutions. Although more recent studies have included people from the community, it is difficult if not impossible to detect all adults with learning disabilities, particularly those with mild disability. The diagnostic criteria used in different studies have also varied—some used screening instruments, while others used structured diagnostic instruments. In addition, studies have varied in terms of whether they included behaviour disorders in the count of psychiatric disorders. Having noted these caveats, recent surveys report a prevalence of 16–45% among adults with learning disability (Cooper et al., 2007; Cooper and Smiley, 2009). There is less information about the incidence of psychiatric disorders, or their prevalence in children with learning disability. Specific disorders with higher rates in individuals with learning disability include schizophrenia, bipolar disorder, autism, and dementia. Behavioural problems are also common, especially hyperactivity, stereotypies, and self-injury (Deb et al., 2001).
In general, the aetiology of psychiatric disorders in learning disability is thought to be similar to that in the general population. That is, they result from a complex and non-deterministic combination of biological, psychological, and social factors (see Chapter 5). Specific links between a learning disability syndrome and a psychiatric disorder (e.g. Down’s syndrome and Alzheimer’s disease) probably reflect a shared aetiological or pathological basis of the two conditions.
Schizophrenia affects 3–4% of people with learning disability, compared with less than 1% in the general population (Deb et al., 2001). The overlap between the two conditions largely reflects shared genetic factors. Clinically, delusions may be less elaborate than in patients with schizophrenia of normal intelligence, hallucinations may have a simpler content, and thought disorder is difficult to identify. When IQ is less than 45, it is difficult to make the diagnosis with any certainty. Furthermore, some of the symptoms of underlying brain damage, such as stereotyped movements and social withdrawal, may wrongly suggest schizophrenia, so a comparison of current with previous behaviour is always valuable.
The diagnosis of schizophrenia should be considered as one of several possibilities when intellectual or social functioning worsens without evidence of an organic cause, and especially if any new behaviour is odd and out of keeping. When there is continuing doubt, a trial of antipsychotic drugs is sometimes appropriate. The principles of treatment of schizophrenia in people with learning disability are the same as those for patients of normal intelligence (see Chapter 11).
The rate of depressive disorders is comparable to, or slightly higher than, that of the general population (Deb et al., 2001; Tonge, 2009). However, people with learning disability are less likely than those of normal intelligence to complain of mood changes or to express depressive ideation. Diagnosis has to be made mainly on the basis of an appearance of sadness, changes in appetite and sleep, and behavioural changes of retardation or agitation. Severely depressed patients with adequate verbal abilities may describe hallucinations or delusions. Mania has to be diagnosed on the basis of hyperactivity and behavioural signs of excitement, irritability, or nervousness.
The differential diagnosis of mood disorder in people with learning disability includes thyroid dysfunction, which is especially prevalent in people with Down’s syndrome, and grief (Brickell and Munir, 2008).
The rate of suicide in people with moderate and more severe learning disabilities is lower than in the general population. The rate of deliberate self-harm is less certain, because it is difficult to decide the patient’s intentions and their knowledge of the likely effects of the injurious behaviour.
The principles of treatment of mood disorders are the same as those for people of normal intelligence (see Chapter 10).
Anxiety disorders and related conditions
Adjustment disorders are common among people with learning disability, occurring when there are changes in the routine of their lives. Anxiety disorders are also frequent, especially at times of stress. Obsessive–compulsive disorders are also found. Conversion and dissociative symptoms are sometimes florid, taking forms that can be interpreted in terms of the patient’s understanding of illness. Somatoform disorders and other causes of functional somatic symptoms can result in persistent requests for medical attention. Treatment is usually directed mainly to bringing about adjustments in the patient’s environment, and reassurance. Counselling, at an appropriate level of complexity, can also be helpful.
Overeating and unusual dietary preferences are frequent among people with learning disability. Abnormal eating behaviours, including ‘pica’, are not uncommon (Grave-stock, 2003), but classical eating disorders appear to be less common than in the general population. Overeating and obesity are features of the Prader–Willi syndrome, a genetic cause of learning disability.
Personality disorder occurs among people with learning disability, but is difficult to diagnose. In this population there is a considerable overlap between the diagnosis of behaviour disorder and that of personality disorder (Reid and Ballinger, 1987). Sometimes the personality disorder leads to greater problems in management than those caused by the learning disability itself. The general approach is as described on p. 704, although with more emphasis on finding an environment to match the patient’s temperament, and less on attempts to bring about change through self-understanding.
Delirium and dementia
Delirium. This may occur as a response to infection, medication, and other precipitating factors. As in people of normal intelligence, delirium in people with learning disability is more common in childhood and in old age than at other ages. Disturbed behaviour due to delirium is sometimes the first indication of physical illness. Delirium may also occur as a side-effect of drugs (especially anti-epileptics, antidepressants, and other psychotropic medication).
Dementia. As the life expectancy of people with learning disability increases, dementia in later life is becoming more common. Alzheimer’s disease is particularly common among people with Down’s syndrome (see p. 695), but dementia may also occur more commonly in other elderly learning-disabled people (Barcikowska et al., 1989). Dementia in people with learning disability may initially present with seizures, or with the usual progressive decline in intellectual and social functioning, which has to be distinguished from conditions such as depression and delirium.
Disorders that are usually first diagnosed in childhood and adolescence
Many of the disorders in this category are more frequent in children with learning disability than in the general population, and they are more likely to continue into adulthood. It is important to be aware that relatively specific developmental disorders of scholastic skills, speech, and language and motor function may occur alongside more global learning disability.
Autism and attention-deficit hyperactivity disorder (ADHD)
Hyperactive behaviour and autistic-like behaviour are frequent symptoms of learning disability. In addition, the diagnoses of autism and ADHD are more common than among the general population. There is a particular comorbidity between learning disability and autistic spectrum disorders, probably reflecting an overlap in their aetiology, especially with regard to genetic factors (Matson and Shoemaker, 2009).
Stereotypes, mannerisms, and rhythmic movement disorders (including head banging and rocking) occur in about 40% of children and 20% of adults with severe learning disability. Repeated self-injurious behaviours are less common but important. There is a specific association with Lesch–Nyhan syndrome, in which the biting away of the corner of a lip is common. Prader–Willi syndrome is strongly associated with a pattern of self-injury where patients pick at their skin.
The term challenging behaviour (or problem behaviour) is used to describe behaviour that is of an intensity or frequency sufficient to impair the physical safety of a person with learning disability, to pose a danger to others, or to make participation in the community difficult. It is probable that around 20% of learning-disabled children and adolescents and 15% of learning-disabled adults have some form of challenging behaviour. The causes of such behaviour are listed in Table 23.2. Whenever possible, the primary cause should be treated. Behavioural treatment (see p. 704) that is provided in the places where the behaviour most appears often or, in severe cases, in a residential unit, is sometimes helpful. For more information, see Emerson (1995) and Tonge (2009).
Serious sleep problems, such as obstructive sleep apnoea, excessive daytime sleepiness, and parasomnias, are not uncommon among people with learning disability and can be a source of considerable distress (Brylewski and Wiggs, 1998). Furthermore, sleep disorders may be associated with subsequent challenging behaviours and a worsening of cognitive impairment. The high rate of sleep disorders is accounted for by five factors:
• coexisting damage to CNS structures that are important for the sleep–wake cycle
• epileptic seizures that start during sleep
• epilepsy-related sleep instability that disrupts sleep architecture
• structural abnormalities in the upper respiratory tract causing sleep apnoea (particularly common among people with Down’s syndrome)
• poor sleep hygiene.
Treatment follows the usual principles of identifying and treating the cause, and improving sleep hygiene (see Chapter 14). Melatonin may have a role if medication is indicated (Braam et al., 2009).
Table 23.2 Causes of challenging behaviour
Pain and discomfort
Under- or over-stimulation
Wish to escape an unpleasant situation
Desire for attention or other reward
Frustration due to difficulty in communication
Side-effects of medication
People with mild learning disability have higher rates of criminal behaviour than the general population (see also Chapter 24, p. 712). The causes of this excess are multiple, but influences in the family and social environment are often important. Impulsivity, suggestibility, vulnerability to exploitation, and desire to please are other reasons for involvement in crime. Compared with the general population, learning-disabled people who commit offences are more likely to be detected and, once apprehended, may be more likely to confess. Among the more serious offences, arson and sexual offences (usually exhibitionism) are said to be particularly common.
Because people with learning disability may be suggestible and may give false confessions, particular care should be taken when questioning them about an alleged offence. In the UK, police interrogation should accord with the Police and Criminal Evidence Act, which requires the presence of an appropriate adult to ensure that the person with learning disability understands the situation and the questions. Once a learning-disabled person has been convicted, psychiatric supervision in specialized forensic learning disability units and specialized education may be needed.
Other clinical aspects of learning disability
Sex, relationships, and parenthood
Most people with learning disability develop sexual interests in the same way as other people. Yet although people with learning disability are encouraged to live as normally as possible in other ways, sexual expression is usually discouraged by parents and carers, and sexual feelings may not even be discussed.
In the past, sexual activity of people with learning disability was strongly discouraged because it was feared that they might produce disabled children. It is now known that many kinds of severe learning disability are not inherited, and that those which are inherited are often associated with infertility. Another concern is that people with learning disability will not be good parents. A study in Norway found that 40% of 126 children born to parents with learning disability suffered from ‘failures of care’ (Morch et al., 1997). However, some people with learning disability can care for a child successfully, so long as they are strongly supported.
It is especially important to consider issues of capacity and ability to consent to sexual relationships if a person with a learning disability becomes involved in such a relationship. These issues should be considered carefully in each case, and contraception made available where appropriate. Some learning disability teams run groups to help people with learning disabilities who wish to find a partner. Individuals in these groups are assessed carefully in order to create a safe environment, which is essential for those who are vulnerable.
Some people with learning disability have a childlike curiosity about other people’s bodies, which can be misunderstood as sexual. Some expose themselves without fully understanding the significance of their actions. This is usually best dealt with by behavioural interventions or with specialized group therapy for those who are more able.
Maltreatment and abuse
Many children with learning disability are raised in families characterized by the factors that are associated in the general population with the maltreatment of children, but there is no convincing evidence that sexual or physical abuse is more frequent in families with a learning-disabled child. Instead, the sequelae of abuse are often found in people with learning disability who were brought up in an institution. When abuse has occurred, it may lead to psychological problems later in life which are similar to those experienced by any other victim of such abuse—for example, depression and post-traumatic stress disorder (Sequiera et al., 2003). However, due to difficulty in emotional expression and communication, such disorders may present with challenging behaviours in situations with which the individual associates past abuse.
Several problems arise more frequently as people with learning disability live longer, other than just the emergence of dementia and physical health problems (Hubert and Hollins, 2009). When the parents are the carers, they may find care increasingly burdensome as they grow old. Such parents are often concerned about the future of their learning-disabled child when they have died, yet are reluctant to arrange alternative care while they are still alive.
The older person with learning disability also faces special problems. If their parents die first, they face problems of bereavement. The isolation felt by many bereaved individuals may be increased because other people are not sure how to offer comfort, and because the learning-disabled person may be excluded from the ritual of mourning. These bereaved people should be helped to come to terms with the loss, using the principles that apply generally to grief counselling, but choosing appropriately simple forms of communication (Hollins and Esterhuyzen, 1997).
Effects of learning disability on the family
When a newborn child is found to be disabled, the parents are inevitably distressed. Feelings of rejection are common, but seldom last for long, and are replaced by feelings of loss of the hoped-for normal child. Frequently the diagnosis of learning disability is not made until after the first year of life, and the parents then have to make great changes in their hopes and expectations for the child. They often experience prolonged depression, guilt, shame, or anger, and have difficulty in coping with the many practical and financial problems. They also grieve for the intact child they had hoped and planned for. A few reject their children, some become overinvolved in their care, sacrificing other important aspects of family life, while others seek repeatedly for a cause to explain the learning disability. Most families eventually achieve a satisfactory adjustment, although the temptation to overindulge the child remains. However well they adjust psychologically, the parents are still faced with the prospect of prolonged hard work, frustration, and social problems. If the child also has a physical handicap, these problems are increased.
There have been several studies on the effect of a child’s learning disability on the family. In an influential study, Gath (1978) compared families who had a Down’s syndrome child at home and families with a normal child of the same age. She found that most families with a learning-disabled child had adjusted well and were providing a stable and enriching environment for their child(ren), although the other siblings were at some disadvantage because of the time and effort devoted to the disabled child. These findings have been supported by subsequent research. Teams specializing in services for children wit learning disability often offer a support service or support groups for siblings.
More recent studies have broadly confirmed the findings of Gath (1978), and have found that mothers with a learning-disabled child at home received help from their partner but little help from other people or services, and many professionals were seen by the parents as lacking interest and expertise. Financial difficulties are also common (Sloper and Beresford, 2006).
As the parents grow older, many fear for the future of their now adult disabled son or daughter. They need advice about ways in which they can arrange additional help when they become unable to provide the support that they gave when they were younger, and about ways of helping their son or daughter to remain in the family home after they have died.
For a review of the effects of learning disability on the family, see Gath and McCarthy (2009).
Aetiology of learning disability
In a study of the 1280 mentally retarded people living in the Colchester Asylum, Penrose (1938) found that most cases were due not to a single cause but to a hypothesized interaction of multiple genetic and environmental factors. This conclusion still broadly applies, especially for mild learning disability. Conversely, a specific cause for severe learning disability is often found. Table 23.3 lists the main categories of learning disability aetiology, and some examples of each.
Genetic factors are a major cause of learning disability. This is in part because intelligence is heritable (with estimates of around 30–50%; Deary et al., 2009), and learning disability is in this respect just the tail end of the normal distribution of intelligence in the population (indeed, by definition, 2% of people are expected to have an IQ of less than 70). This aspect of genetic predisposition to intelligence reflects the cumulative effects, and interactions, of a large number of genes, most of which have yet to be identified. In addition, a specific chromosomal or genetic defect can be the necessary and sufficient cause of a person’s learning difficulty. These include Down’s syndrome and fragile X syndrome, the two commonest causes of learning disability. This crude division of learning disability into cases where a specific cause can be found, and those where it reflects multiple, largely ‘non-specific’ causes, parallels the categorization into either ‘subcultural’ or ‘pathological’ mental retardation (as it was then called) made by Lewis (1929).
At a mechanistic level, the types of genetic abnormality that cause learning disability are diverse (see Box 23.1). The clinical features of the major genetic causes of learning disability are listed in Table 23.4, with additional details given in the text for Down’s syndrome and fragile X syndrome. For a review of the genetic causes of learning disability, see Ropers (2010).
Environmental factors are conveniently divided into pre-, peri- and postnatal factors, reflecting the time at which they are believed to have occurred. The relative importance of environmental factors varies according to setting. For example, they are more significant where healthcare provision or general health are poorer, and they may be affected by local factors (e.g. areas of low iodine predispose to congenital hypothyroidism). Social as well as biological factors should be considered in the environmental category. Even though the evidence remains inconclusive, it is notable that low intelligence is related to, and predicted by, psychosocial factors such as lower social class, poverty, and an unstable family environment (Sameroff et al., 1987). Some non-genetic causes of learning disability are summarized in Table 23.5.
Note also that aetiology of learning disability is sometimes defined in terms of an accompanying physical characteristic, such as hydrocephalus, microcephaly, or cerebral dysgenesis. Finally, the descriptive category of inborn errors of metabolism encompasses multiple different syndromes, mostly due to a single gene disorder affecting an enzyme that is important in a particular biochemical pathway. They include urea cycle disorders, and lysosomal storage disorders, which in turn include mucopolysaccharidoses (e.g. Hurler’s syndrome) and sphingolipidoses (e.g. Tay–Sachs disease), and others (e.g. phenylketonuria. For a review, see Kahler and Fahey (2003).
Overall, it is estimated that prenatal (genetic and environmental) factors cause 50–70% of learning disability, with 10–20% originating perinatally, and 5–10% originating postnatally; the proportions, and the causes within each category, depend on the population being studied. For reviews of the aetiology of learning disability, see Clarke and Deb (2009), Kaski (2009), and Tonge (2009).
In 1866, Langdon Down tried to relate the appearance of certain groups of patients to the physical features of ethnic groups. One of his groups had the condition originally called mongolism, and now generally known as Down’s syndrome. This condition is a frequent cause of learning disability, occurring in 1 in about every 650 live births. It is more frequent among older women, occurring in about 1 in 2000 live births to mothers aged 20–25 years, and 1 in 30 live births to those aged 45 years. The incidence of Down’s syndrome has decreased because of increased rates of detection of the condition by amniocentesis and subsequent termination of pregnancy.
Table 23.3 The types of causes of learning disability
The clinical picture consists of a number of features, any one of which can occur in a normal person. Four features together are generally accepted as strong evidence for the syndrome. The most characteristic signs are listed in Table 23.6. IQ is generally between 20 and 50, but in 15% of individuals it is above 50. Mental abilities usually develop fairly quickly in the first 6 months to a year of life, but then increase more slowly. Children with Down’s syndrome are often described as loveable and easygoing, but there is wide individual variation. Emotional and behaviour problems are less frequent than in forms of retardation associated with clinically detectable brain damage.
Box 23.1 The genetic basis of learning disability
Genetic factors of various kinds underlie learning disability. (See also pp. 98–104 for an introduction to relevant genetic concepts and terminology.)
Chromosomal abnormalities. An abnormal number of chromosomes (aneuploidy) invariably causes learning disability. Trisomy refers to possession of an extra copy of a chromosome; the classic example is trisomy 21 (Down’s syndrome). Absence of an autosome is not compatible with life, but an absence (or excessive number) of a sex chromosome is, and produces a variable phenotype in which mild learning disability is common (e.g. XO, Turner’s syndrome).
Learning disability is 25% more common in boys, and Lehrke (1972) was the first to suggest that this might be due to X-chromosome-linked causes. This suggestion has proved to be largely correct, with fragile X syndrome being the commonest disorder, but many others have been identified as well. X-linked learning disability is a collective term used to describe these disorders. Their clinical picture can be particularly complex (e.g. in terms of girls being affected, and the severity of the phenotype) (Stevenson and Schwartz, 2008).
Deletions and duplications refer to part of a chromosome being missing or repeated, with the abnormality being large enough to be visible under the microscope using various techniques. (Note that we have two copies of each autosomal chromosome, one from each parent, and only one is affected, hence the term ‘hemideletion.’ Occasionally, the clinical picture depends upon which parental chromosome is affected, via a process called imprinting.) Some parts of the genome are ‘hotspots’ for deletions and rearrangements, such as the q11 band of chromosome 22, which causes velocardiofacial syndrome.
The tips of the chromosomes (telomeres) also seem to be particularly vulnerable, with subtelomeric deletions thought to cause 5–10% of ‘idiopathic’ learning disability.
Copy number variation (CNV) refers to deletions or duplications of genetic material which are on a continuum with the recognized chromosomal abnormalities but which are far too small to be seen using conventional methods (see Chapter 5, p. 101). CNVs are now thought to be an important contributor to learning disability, and to explain much of its overlap with autism and other disorders (Vissers et al., 2010). As in these other disorders, a CNV can either ‘cause’ learning disability (e.g. CNVs on 15q13 and 16p21), or simply act as a risk factor, depending on its size and location in the genome.
Single gene disorders are those which are attributed to a defect limited to a single gene, and where the identity of the gene, and often the causative mutation within it, is known. This category includes most inborn errors of metabolism. Single gene disorders can be dominant or, more commonly, recessive, and can be autosomal or X-linked.
Note that these points illustrate that genetic factors do not in fact fall into discrete categories, but are more like a spectrum of causality. Thus the size of the abnormality can be anything from a whole chromosome, to a visible deletion of part of one, to a CNV, to a mutation in a single nucleotide. The genetic defect can either be the complete cause of the learning disability, or merely act as a minor risk factor. And since many of the genetic deficits arise de novo (i.e. are spontaneous mutations) in the individual (due to an error during gametogenesis, fertilization, or early development), they blur the distinction between genetic (in the sense of inherited) and environmental causes.
In the past, the infant mortality of Down’s syndrome was high, but with improved medical care survival into adulthood is usual, and about 25% of people with Down’s syndrome now live beyond 50 years of age.
In 1959, Down’s syndrome was found to be associated with the chromosomal disorder of trisomy (three chromosomes instead of the usual two). About 95% of cases are due to trisomy 21. These cases result from failure of disjunction during meiosis, and are associated with increasing maternal age. The risk of recurrence in a subsequent child is about 1 in 100. The remaining 5% of cases of Down’s syndrome are attributable either to translocation involving chromosome 21 or to mosaicism. The disorder leading to translocation is often inherited, and the risk of recurrence is about 1 in 10. Mosaicism occurs when non-disjunction takes place during any cell division after fertilization. Normal and trisomic cells occur in the same person, and the effects on cognitive development are particularly variable. Down’s pathology is assumed to be due to the increased ‘dosage’ of genes, and thus increased production of the proteins that they encode. This probably also accounts for the frequent early onset of dementia in Down’s syndrome (Holland et al., 1998), because the amyloid precursor protein (APP) gene that encodes β-amyloid and is central to Alzheimer’s disease is located on chromosome 21 (Zigman and Lott, 2007).
Table 23.4 Notes on some genetic causes of learning disability
Fragile X syndrome and X-linked learning disability
Fragile X syndrome is the second most common specific cause of learning disability after Down’s syndrome, and is the most common inherited cause. It occurs in around 1 in 4000 males and in a milder form in about 1 in 6000 females. It accounts overall for about 10% of those with learning disability. The condition was so named because the X chromosome is ‘fragile’ when lymphocytes from affected individuals are cultured without sufficient folic acid.
As shown in Table 23.7, there are a number of characteristic but highly variable clinical features, none of which is diagnostic, including enlarged testes, large ears, a long face, and flat feet. Psychological features include abnormalities of speech and language, autistic behaviour and other social impairments, disorders of attention and concentration, and hyperactivity.
The inheritance of the condition, and the characteristics of carriers, are unusual and complex (Hagerman et al., 2009). Fragile X syndrome is caused by an amplified CGG repeat sequence in the FMR1 gene, which leads to silencing of the gene and thus an absence of FMR1 protein. FMR1 regulates genes involved in synaptic function and plasticity, and the syndrome is thought to arise because the lack of FMR1 interferes with the action of these other genes (Bear et al., 2008). Some of these genes are now therapeutic targets for fragile X syndrome, but as yet there are no established treatments (Hagerman et al., 2009). Folic acid is ineffective (Rueda et al., 2009).
Table 23.5 Some non-genetic causes of learning disability
It is now realized that fragile X is one of a family of X-linked causes of learning disability, which together occur in up to 1 in 600 boys, account for about 16% of cases of male learning disability, and contribute to the male excess of the condition, although these disorders can also affect girls (Gecz et al., 2009; Ropers, 2010). An extreme example of the latter is Rett syndrome, which only affects girls, probably because it is lethal to male embryos.
Table 23.6 Features of Down’s syndrome
Moderate or severe learning disability
Slanted eyes and epicanthic folds
• Small mouth with furrowed tongue
• Flat nose
• Flattened occiput
• Stubby hands, fingers, and single transverse palmar crease
• Hypotonia with hyperextensibility of joints
Associated medical problems
• Cardiac anomalies, especially septal defects
• Gastrointestinal abnormalities
• Atlantoaxial instability
• Susceptibility to infection
• Impaired hearing
Increased risk of leukaemia, hypothyroidism, and autoimmune disorders
Table 23.7 Features of fragile X syndrome
More common in males
Caused by FMR1 gene mutation
• Variable from mild to profound
• Increases late in childhood
• Performance IQ affected more than verbal IQ
• Poor attention and concentration
• Speech repetitive, lacking themes or content (‘litany speech’)
• Autistic features common
• Large, protruding ears
• Long face with high-arched palate
• Flat feet
• Lax joints
• Soft skin
• Large testes (after puberty)
• Mitral valve prolapse
Note: All features are particularly variable.
Assessment and classification of people with learning disability
Assessment of a person with suspected learning disability is directed towards five main areas:
• the cause and severity of the disorder
• intellectual and social skills development
• associated medical conditions
• associated psychiatric disorders
• assessment of needs.
A multi-axial classification is available to record some of this information, the DC-LD (Diagnostic Criteria for Psychiatric Disorders for Use with Adults with Learning Disabilities) (Royal College of Psychiatrists, 2001), namely:
Axis I: Severity of learning disability
Axis II: Cause of learning disability
Axis III: Psychiatric disorders:
Level A: Developmental disorders
Level B: Psychiatric illness
Level C: Personality disorders
Level D: Problem behaviours
Level E: Other disorders.
This system helps to ensure that all of the key components are considered and recorded. It also highlights the fact that the assessment is both about characterizing the learning disability and its consequences, and also about making a specific diagnosis, where possible, as to its aetiology.
Severe learning disability can usually be diagnosed in infancy, especially as it is often associated with detectable physical abnormalities or with delayed motor development. Some people with learning disability have specific developmental disorders—that is, impairment of specific functions greater than would be expected from the general intellectual level. The clinician should be cautious when diagnosing less severe learning disability on the basis of delays in development. Although routine examination of a child may reveal signs of developmental delay, suggesting possible learning disability, confident diagnosis often requires specialist assessment.
Full assessment involves several stages, including history taking, examination of the mental state, physical examination, genetic and other laboratory investigations, developmental testing, functional behavioural assessment, analysis of the interactions between the disabled person and the family and the social support systems, and other aspects of adjustment. Each of these stages will be considered in turn. Although this section is concerned mainly with the assessment of children, similar principles apply to assessments later in life.
For reviews of the assessment of learning disability, see Holland (2009) and Kaski (2009).
In the course of obtaining a full history, particular attention should be given to any family history suggesting an inherited disorder, and to abnormalities in the pregnancy or the delivery of the child. Dates of passing developmental milestones should be ascertained. A full account of any behaviour disorders should be obtained. Details of any associated medical conditions, such as congenital heart disease, epilepsy, and cerebral palsy, should be documented.
Mental state examination
The approach should be flexible. Many people with learning disability attend and concentrate poorly. Therefore the interview may need to be carried out rather informally while the person is engaged intermittently in some other interest. Questions should be simplified to take account of each person’s receptive language and developmental level. Behavioural observations by family, friends, and carers are often most helpful to the observations that the assessor is able to make. Clinical assessment can also be supplemented by using standardized scales for the assessment of psychopathology, adapted for use in patients with learning disability.
A systematic physical examination should include noting the child’s overall appearance, looking for dysmorphic features and other physical signs suggestive of specific disorders (see Tables 23.4, 23.5, 23.6, and 23.7). Head circumference should be recorded. The parents’ appearance may also be worth noting. Neurological examination is important and should include particular attention to impairments of vision and hearing.
As in the assessment of patients of normal intelligence, it is important to find out the person’s previous baseline state before concluding that an item of current behaviour is evidence of a psychiatric disorder. Some longstanding behaviours, such as stereotyped movements or social withdrawal, may resemble and be mistaken for symptoms of schizophrenia or other psychiatric disorders—so-called diagnostic overshadowing (Reiss and Szyszko, 1983). However, an increase in a long-standing behaviour may be the first, and sometimes the only, evidence of psychiatric disorder—so-called baseline exaggeration(Sovner and Hurley, 1989).
Genetic and laboratory investigations
Because many cases of learning disability, especially moderate and severe forms, are caused by a specific chromosomal or genetic abnormality, genetic investigations are a major component of assessment. A clinical geneticist can provide up-to-date information about the conditions for which screening is available and the cytogenetic and molecular genetic methods in use (since both are evolving rapidly) (see, for example, Stevenson and Schwartz, 2009; Hill et al., 2010), as well as help with the interpretation of test results, and sharing the information with the family and addressing their questions. Genetic investigations are also critical in preventative screening for learning disability.
Depending on the clinical suspicion, and informed by knowledge of the common causes of learning disability, a range of blood tests to detect inherited metabolic and endocrine disorders may also be indicated. Neuroimaging, particularly structural magnetic resonance imaging (structural MRI), may also be required. Close involvement with a paediatrician or paediatric neurologist is recommended.
This assessment is based on a combination of clinical experience and standardized methods of measuring intelligence, language, motor performance, and social skills. Although the IQ is the best general index of intellectual development, it is not reliable in the very young or among people who have severe to profound degrees of learning disabilities.
Tests used in developmental assessment
Standardized assessment instruments are widely used for screening, diagnosing, and assessing the severity of disorders of psychological development. Many require special training for correct administration, but some do not. The choice of test is important because many neuropsycho-logical tests are too difficult for some people with learning disability. The type of test is also important. There are norm-referenced tests such as the Wechsler Adult Intelligence Scale (WAIS) and other IQ measures, criterion-referenced tests which apply to particular skills without reference to population norms, tests of adaptive behaviour in social settings, and assessments of behavioural functioning. An abbreviated version of the WAIS, called the Wechsler Abbreviated Scales of Intelligence (WASI) (Psychological Corporation, 2004), is now available. Another quick useful method is the use of a Picture Vocabulary Test or another non-verbal test such as Raven’s Progressive Matrices. Other commonly used instruments are summarized in Box 23.2. The first four provide a general assessment over a range of developmental domains. The others focus on specific aspects of development. All have good reliability and validity.
Functional behavioural assessment
The functional assessment of behaviour involves an assessment of events before, during, and immediately after the behaviour takes place. It is based on observations reported by family, carers, and members of the clinical team. It is concerned with abilities related to self-care, and social abilities, including communication, sensory motor skills, and social relationships. Sometimes key behaviours are counted and recorded on paper or using a palmtop computer.
Assessment of social interaction and adjustment
This assessment is concerned with the interaction between the person with learning disability and the individuals closely involved in their care. It is also concerned with opportunities for learning new skills, making relationships, and achieving more choice. If the person with learning disability has reasonable language ability, it is usually possible to obtain much of the information from him or her. If language ability is less well developed, the account has to be obtained mainly from informants. It is particularly important to obtain a complete description of any change from the usual pattern of behaviour. It is often appropriate to ask parents, teachers, or care staff to keep records of behaviours such as eating, sleeping, and general activity so that problems can be identified and quantified. The assessor should keep in mind the possible causes of psychiatric disorder outlined above, including unrecognized epilepsy.
Box 23.2 Commonly used instruments for developmental assessment
Assessment of needs
As the diagnostic assessment progresses, the likely needs of the patient require careful consideration, too, as these will form the basis of the care package and management plan to be implemented. The needs assessment brings together the social, emotional, and health needs of the person, and takes into account their views and wishes as well as those of their significant others. This approach, sometimes termed ‘person-centred planning’, is now integral to most learning disability services (Robertson et al., 2007).
A modification of the Camberwell Assessment of Need, known as CANDID (Camberwell Assessment of Need for Adults with Developmental and Intellectual Disabilities), is available for use in adults with learning disability.
Once learning disability has been diagnosed, regular reviews are required. For children, these are usually carried out by a multidisciplinary child health team together with teachers and social workers. The child psychiatrist liaises with the team, and has a particular role where the child has emotional, behavioural, or other psychiatric problems. When the child reaches school-leaving age, a thorough review is important. This should assess the need for further education, the prospects for employment and independent living, and the need for ongoing specialist physical and psychological healthcare. Adults with learning disability need to be assessed regularly to make sure that their care remains appropriate; a learning disability psychiatrist will usually contribute to these multidisciplinary reviews.
The care of people with learning disability
A historical perspective
Current arrangements for care are best understood in a historical context (Thomson, 1998), which usefully begins in the early nineteenth century. At this time there were numerous reports of improved forms of care, notably by Itard, physician-in-chief at the Asylum for the Deaf and Dumb in Paris, who attempted to train a ‘wild boy’ found in Aveyron in 1801. This child was thought to have grown up in the wild, isolated from human beings. Itard made great efforts to educate the boy, but after persisting for 6 years he concluded that the training had failed. Nevertheless, his work had important and lasting consequences, for it led others to try educational methods. These methods were developed, for example, by Seguin, director of the School for Idiots at the Bicêtre in Paris, who in 1842 published the Theory and Nature of the Education of Idiots. Seguin believed that the mentally retarded had latent abilities which could be encouraged by special training, involving physical exercise, moral instruction, and graded tasks. These ideas were taken up in other countries, particularly Switzerland and Germany, with the opening of institutions that attempted to train their pupils and thereby enable them to live as independently as possible, while recognizing that many would need long-term care.
At the end of the nineteenth century, several influences led to a more custodial approach. These influences included the development of the science of genetics, the eugenics movement, the measurement of intelligence, and a general decrease in public tolerance of abnormal behaviour. In England and Wales, such ideas were reflected in the Mental Deficiency Act 1913, which empowered local authorities to provide for the confinement of the ‘intellectually and morally defective’, and imposed upon the authorities a responsibility to provide training and occupation. In the years that followed, the total number of people of this kind in institutions rose from 6000 in 1916 to 50 000 in 1939, and remained at high levels well into the post-war period.
In the 1960s the need for reform was recognized in several developed countries, prompted in part by the changes away from institutions and towards community care that had already been effected in general psychiatry. Campaigning by groups of parents, and public concern about the generally—and in some instances scandalously—poor conditions in which people with learning disabilities were housed, was also important. Surveys of hospitals for the ‘retarded’ showed that the mean IQ of their patients was over 70, and thus many residents had only mild learning disability and did not need hospital care. At around the same time it was shown that training was beneficial in learning disability across the severity range (O’Connor, 1968), and that there was an advantage to providing residential care in small homely units (Tizard, 1964).
It is now recognized in all developed countries that people with learning disability should be integrated into society as far as possible. However, there have been divergent views about the best way to achieve greater integration. In the UK, resources have been inadequate and progress has been slow. In the USA, deinstitutionalization was carried out more quickly, with both successes and failures.
The main current principle of care is normalization, an idea that was developed in Scandinavia in the 1960s. This term refers to the general approach of providing a pattern of life as near normal as possible (Nirje, 1970). Normalization implies that almost all people with learning disability will live in the community, participating in normal activities and relationships, making choices, and having full social opportunities. Children are brought up whenever possible with their families, and adults are encouraged to live as independently as is feasible. For the few who need special social and health care, accommodation and activities are designed to be as close as possible to those of family life. The concept of normalization has been further developed in the USA and elsewhere, and includes specialist help to enable people to achieve their full potential. Increasingly, disabled people are organizing themselves into advocacy groups, and those who are unable to speak for themselves about the services have advocates to speak for them. A recent systematic review confirmed the better outcomes of community-based services compared with institutional care (Kozma et al., 2009).
The precise model for the care of people with learning disability in a community matters less than the level of detail in which it is planned and the enthusiasm with which it is carried out. Good planning requires both an estimate of the needs of the population to be served, and a summation of individual assessments of those identified, as each person has individual needs. To achieve this, local case registers and linked developmental records are needed.
The general approach to care is educational and psychosocial, together with appropriate psychiatric interventions for mental health problems. The family doctor and paediatrician are mainly responsible for the early detection and assessment of learning disability. The team providing continuing healthcare includes psychiatrists, psychologists, speech therapists, nurses, occupational therapists, and physiotherapists. Volunteers and self-help groups for carers can play a valuable part. In the UK, residential provisions for people with learning disability are from several sources, including the education service, health service, social services, and voluntary organizations.
For a review of services for learning disability, see Bouras and Holt (2009), and for a practical guide to their organization, see Bernard and Turk (2009).
The main elements in a comprehensive service for people with learning disability are as follows:
• the prevention and early detection of learning disability
• regular assessment of the learning-disabled person’s attainments and disabilities
• advice, support, and practical measures for families
• provision for education, training, occupation, or work
• housing and social support to maximize self-care
• medical, nursing, and other services for those who require these forms of help as outpatients, day patients, or inpatients
• psychiatric and psychological services.
Primary prevention consists of genetic counselling, the education of pregnant women (and the population in general) about behaviours that may put the fetus at risk, early detection of fetal abnormalities during pregnancy, and good obstetric and perinatal care. Secondary prevention aims to prevent the progression of disability by either medical or psychological means. The latter include ‘enriching’ education and early attempts to reduce behavioural problems. In developed countries, there remains considerable scope for reduction of the genetic causes of severe learning disability, but it is unlikely that it will be possible to affect the incidence of mild learning disability significantly. In developing countries, the incidence of learning disability could be substantially reduced by general measures to improve the health of mothers during pregnancy, and by better perinatal care. For a review, see Kaski (2009).
Genetic screening and counselling
These measures begin with an assessment of the risk that a learning-disabled child will be born. Such an assessment is based on study of the family history, on knowledge of the genetics of conditions that give rise to learning disability, and on awareness of the possibilities for genetic screening. The risks of screening are explained to the parents, who are encouraged to discuss them. Most parents seek advice only after a first abnormal child has been born. Those who seek advice before starting to have children usually do so because there is a person with learning disability in the family. A positive diagnosis of an abnormality leading to termination or indeed a false-positive result of screening causes considerable distress. It is important, therefore, that those involved in screening are alert to psychological issues and have the appropriate counselling skills. Close liaison with a clinical geneticist is recommended.
Prenatal care begins even before conception, with immunization against rubella for girls who lack immunity, and advice on diet, alcohol, and smoking.
Prenatal diagnosis overlaps with genetic screening. It is becoming available for an increasing number of conditions with the aim of providing information to those at risk of having abnormal children, reassurance to others, and appropriate treatment of affected infants through early diagnosis. Amniocentesis, fetoscopy, and ultrasound scanning can reveal chromosomal abnormalities, most open neural-tube defects, and about 60% of inborn errors of metabolism. Amniocentesis carries a small but definite risk, and so is usually offered only to women who have carried a previous abnormal fetus, women with a family history of congenital disorder, and those over 35 years of age.
Rhesus incompatibility is now largely preventable. Sensitization of a rhesus-negative mother can usually be avoided by giving anti-D antibody. An affected fetus can be detected by amniocentesis and treated if necessary by exchange transfusion. For pregnant women with diabetes mellitus, special care can improve the outlook for the fetus. Further information about these aspects of care can be found in textbooks of obstetrics and paediatrics.
In the UK, all infants are routinely tested for phenylketonuria, and testing for hypothyroidism and galactosaemia is becoming increasingly common. Screening for elevated levels of lead has been advocated, especially in areas where they are known to be high. Intensive-care units and improved methods of treatment for premature and low-birth-weight infants can prevent learning disability in some who would previously have suffered brain damage. However, these methods also enable the survival of some disabled children who would otherwise have died.
Compensatory education is intended to provide optimal conditions for the mental development of the disabled child. An early example was the Head Start programme in the USA, which provided extra education for deprived children, including nursery schooling and attempts to teach specific skills. Many of the results were disappointing, and it was followed by a more intensive programme with similar aims, carried out in Milwaukee (Garber, 1988). Skilled teachers taught children living in slum areas with mothers who had a low IQ (less than 75). This additional education started at 3 months of age and continued until the child reached school age. At the same time, the mothers were trained in a variety of domestic skills. These children were compared with children of the same age from similar families who had not received these interventions. At the age of four and a half, the trained children had a mean IQ 27 points higher than that of the controls. This study can be faulted because the selection of children was not strictly random, and because some of the changes in test scores could have been due to practice. Nevertheless, the main findings probably stand—substantial effort by trained staff can produce worthwhile improvement in children of low intelligence born to socially disadvantaged mothers. Overall, it seems that early interventions can be effective, especially if they are family centred. However, many uncertainties remain about the components and the delivery of such help.
Help for families
As noted earlier, having a child with learning disability has a major emotional and practical impact on the family, and support is needed for the family from the time that the diagnosis is first made (Gath and McCarthy, 2009). It is not enough to give worried parents a full explanation on just one occasion. They may need to hear the explanation several times before they can absorb all of its implications. Adequate time must be allowed to explain the prognosis, indicate what help can be provided, and discuss the part that the parents can play in helping their child to achieve his or her full potential. Paediatricians, health visitors, and sometimes clinical geneticists are involved in this process.
Thereafter, the parents need continuing support. When the child starts school, the parents should be kept informed about progress, and feel involved in the planning and provision of care. They should be given help with practical matters, such as day care during school holidays, babysitting, or arrangements for family holidays. In addition to practical assistance, the parents need continuing psychological support, which may be provided as a programme for the whole family.
Families are likely to need extra help when their child reaches puberty or leaves school. Making the transition from child to adult services is often extremely stressful. Both day and overnight care are often required to relieve carers and to encourage the learning-disabled person to become more independent.
Education, training, and occupation
One aspect of the policy of normalization is that children with learning disability should be educated as far as possible within mainstream schools. The extent to which this is done varies in different countries and also in different regions of the same country.
Research has consistently shown the value of an early start to the education of children with learning disability, who should attend a play group or nursery class. When school age is reached, the least disabled children can attend remedial classes in ordinary schools. Others need to attend special educational programmes for children with learning disabilities. It is still not certain which learning-disabled children benefit from ordinary schooling. Education in an ordinary school offers the advantages of more normal social surroundings, social integration, and the expectation of progress, but it may have the disadvantage of a lack of special teaching skills and equipment. Also, the methods of teaching that emphasize self-expression are inappropriate for some children with learning disability who need special teaching of language and communication (Howlin, 1994). Another advantage of educating disabled children in ordinary schools is that other pupils learn to accept that their integration into society is the norm.
Before learning-disabled children leave school, they need reassessment and vocational guidance. Most young people with mild learning disability are able to take normal jobs or enter sheltered employment. Adults with severe disability are likely to transfer to adult day centres, which should provide a wide range of activities if the abilities of each attender are to be developed as much as possible.
It is now widely accepted that parents should be supported in caring for their learning-disabled children at home. If care is too heavy a burden for the parents because of their other family commitments, the child with learning disability should, if possible, be in another family. Adults should be supported in ordinary housing, or placed with a family, or in suitable lodgings, or in a small residential group home. Staff need to encourage the residents to develop their social skills and to live as normally as possible.
People with learning disability should have the same access to general and specialist medical services as other citizens, but they require extra support if they are to obtain full benefit. This care is usually obtained from the ordinary medical services and this arrangement can work well, provided that doctors and nurses are sufficiently aware of how to deal with a person with learning disability, and have the time and resources to do so. Families and carers are helped when care is coordinated by a single person, so that they do not receive conflicting advice. Specialist nurses have a particularly important role in such coordination. Shared care between neurologists and psychiatrists can improve outcomes for some patients—for example, in the diagnosis and treatment of epilepsy.
Recent high-profile reports have emphasized the high level of health complications in those with learning disabilities, and their often unmet health needs (e.g. the Healthcare for All report listed in the further reading section at the end of this chapter). It is therefore highly recommended that annual health checks be performed. This helps to screen these individuals for treatable conditions and improve their quality of life, as well as preventing early death.
Psychiatric care is an essential part of a comprehensive community service for people with learning disability. In some countries it is provided by generic mental health services, but in the UK it is generally provided by staff who specialize in the care of people with learning disability. The psychiatrist with such a specialism forms part of a wider learning disability team consisting of learning disability nurses, psychologists, and social workers. Once known to the team, the patient may access the psychiatrist in the event of psychiatric disorders or challenging behaviour. Some psychiatrists with specialist learning disability training may also diagnose, treat, and manage epilepsy, although, as noted above, a neurologist may also be involved in this and in other neurological aspects of management.
Treatment of psychiatric disorder and behavioural problems
Psychiatric disorder in people with learning disability usually comes to notice through changes in behaviour. It should be remembered, however, that behavioural change can also result from physical illness or from stressful events, both of which should be carefully excluded. In the most disabled, and especially those with sensory deficits, behavioural disturbance may be due to under-stimulation and frustration due to the inability to communicate wishes and needs. Once the cause is clear, the treatment follows. Physical illness should be treated promptly, stressful events reduced if possible, or a more stimulating environment provided when appropriate. If the disturbed behaviour results from a psychiatric disorder, the treatment is similar in most ways to that for a patient of normal intelligence with the same disorder. Carers are often involved in behavioural assessment and treatment methods, and it is important to support them adequately.
The most serious and persistent disorders occasionally require hospital admission for more intensive behavioural management, which may be combined with pharmacotherapy.
The indications for psychotropic drugs are generally the same as for patients of normal intelligence, and the full range of such medication should be available for the learning disabled. However, the psychiatrist has particular responsibility for organizing effective ongoing monitoring, including regular physical examination. The latter is especially important for patients with severe communication impairments who cannot describe adverse effects. Also, neurologically impaired patients may develop adverse effects at lower doses and suffer from over-sedation, delirium, and extrapyramidal symptoms. Antipsychotic and benzodiazepine drugs are often useful in the short-term control of behaviour problems, generally at much lower doses than would be prescribed in the general population. There are few controlled trials of the efficacy and tolerability of antipsychotic drugs in the longer-term treatment of abnormal behaviour. Nonetheless, clinical experience suggests that severely behaviourally disturbed patients who do not respond to psychosocial interventions sometimes benefit from prolonged use of medication with frequent monitoring of its effects and adjustment of dosage. For a review, see Bramble (2011).
Anti-epileptic drug treatment is frequently required, given the prevalence of epilepsy in learning disability (see p. 686). Special care is needed to select a drug and dosage that controls seizures without causing unwanted effects. The older anti-epileptic drugs sometimes cause over-sedation and cognitive blunting. Carbamazepine and sodium valproate are now often chosen, with the latter being first-line treatment for seizures that develop in the context of dementia. Because of the problem of drug resistance, second-line and combination therapies may be required, and involvement of an epilepsy specialist is recommended. For a review of the management of epilepsy in learning disability, see Iivanainen (2009).
Although limited understanding of language sets obvious limitations to the use of psychotherapy, it can be useful in some settings. More able patients can benefit from a modified or simplified psychodynamic approach. Cognitive therapies can be attempted with some patients with higher levels of verbal ability. The most useful psychological treatment takes the form of behavioural therapies. These may be, and are, used for a wide variety of problems (e.g. challenging behaviour in a wide variety of patient abilities). Some learning disability nurses take a special interest in such therapies, and some psychologists are extensively trained in the area. Counselling for parents is an important part of treatment. If more formal family therapy is undertaken, families generally prefer structural approaches, which address the problems and solutions that are relevant to them. Some children with profound learning disability can be helped by the use of play and sensory stimulation to encourage developmental advances (Hewett and Nind, 1998).
Behavioural methods are helpful to people with severe learning disability as some of the methods do not require language, and can be used to encourage basic skills such as washing, toilet training, and dressing. Often parents and teachers are taught to carry out the training so that it can be maintained in the patient’s everyday environment. If the problem is an undesired behaviour, a search is made for any environmental factors that seem regularly to provoke it or reinforce it (functional analysis). If possible, these environmental factors are changed and carers helped to avoid rewarding the behaviour. At the same time, alternative adaptive responses are reinforced. Aggressive behaviour is sometimes dealt with by so-called ‘time-out’ in which the patient is ignored or secluded until the behaviour subsides. However, techniques that employ negative reinforcement should not be used (Matson and Taras, 1989). If the problem is an insufficiency of some socially desirable behaviour, attempts can be made to reinforce such behaviour with material or social rewards, if necessary by ‘shaping’ the final behaviour from simpler components. Reward should be given immediately after the desired behaviour has taken place (e.g. using the toilet). For training in skills such as dressing, it is often necessary to provide modelling and prompting in the early stages, and to reduce them gradually later (Petronko et al., 1994).
Ethical and legal issues in learning disability
Normalization, autonomy, and the conflict of interests
The policy of normalization has encouraged learning-disabled people to live as near normal lives as possible. This policy can create conflicts between the interests of the learning-disabled person and those of others, such that it may be difficult to balance the interests of the disabled person with those of their carer(s) and other family members. Normalization can also produce unintended effects. For example, it requires that learning-disabled children should be educated in ordinary schools whenever possible. However, in secondary schools, children with special needs were found to be bullied three times more often than other children (Whitney et al., 1994). It could be argued that it is in the immediate interests of an individual child to be educated in a special school where they are less likely to be bullied, whereas the long-term interests of learning-disabled children as a group may be advanced more by a policy of education in ordinary schools while making strenuous efforts to eradicate bullying.
Normalization also leads to practical ethical questions about sexual activity, contraception, and parenting, as mentioned earlier.
Consent to treatment
Many people with severe learning disability are unable to give informed consent, and it is essential to be aware of local legislation and practice. In the UK, these issues are covered by the Mental Capacity Act (see Chapter 4), under which the practitioner is required to try to explain the nature of the procedure in a way that the patient can understand. If the patient is deemed not to have capacity, then a person closely involved in their care and who knows them well should be consulted. An advocate may also be involved. If there is doubt and inpatient admission is being sought, it is good practice to discuss matters with the local Mental Capacity Act office. Discussing the case with an experienced practitioner is also helpful.
Seriously ill patients who refuse potentially life-saving treatments can prove difficult to deal with in general medical settings. If the patient is sufficiently impaired as not to understand the nature of the choice that they face and there is a medical emergency, a Mental Capacity Act assessment should be completed by the medical team. If there is time, it may be necessary to refer the case for review in court—for example, when the question of termination of pregnancy has to be decided.
Consent to research
Consent to research requires the ability to understand information, to use the information rationally, to appreciate the consequences of situations, and to decide between alternatives (see Chapter 4). The assessment of these abilities among the learning disabled has been described by the American Psychiatric Association (1998). Any individual who has agreed to take part in research should understand that they can withdraw consent if they wish, a point that should be explained with particular care (Arscott et al., 1998). In general no research should be undertaken involving people who cannot consent, unless the same research cannot be successfully carried out without involving these people. It is important to remember that individuals with learning disability vary in their capacity to provide informed consent. Some may be able to provide verbal rather than written consent. Some may need sign language, pictures, or written information in simple language and a large font size. For some the proposal may have to be discussed repeatedly. It is also good practice to have agreement with the carers and the multidisciplinary team members. In every case the research should follow strictly the relevant research governance criteria and, in the UK, the Mental Capacity Act (see Chapter 4).
Bhaumik S and Branford D (2005). The Frith Prescribing Guidelines for Adults with Learning Disability. Taylor & Francis, London.
Bouras N and Holt G (eds) (2007). Psychiatric and Behavioural Disorders in Intellectual and Developmental Disabilities. Cambridge University Press, Cambridge.
Fraser WI and Kerr M (eds) (2003). Seminars in the Psychiatry of Learning Disabilities. Gaskell, London.
Gelder MG, Andreasen NC, López-Ibor JJ Jr and Geddes JR (eds) (2009). Section 10: Intellectual disability (mental retardation). In: The New Oxford Textbook of Psychiatry, 2nd edn. Oxford University Press, Oxford. (The nine chapters in this part of the textbook provide a systematic account of the subject written for the general psychiatrist.)
Hassiotis A, Barron DA and Hall I (2009). Intellectual Disability Psychiatry: a practical handbook. John Wiley & Sons, Chichester.
Michael J (2009). Healthcare for All: report of the independent inquiry into access to healthcare for people with learning disabilities. www.dh.gov.uk/en/Publicationsandstatistics/Publications/PublicationsPolicyAndGuidance/DH_099255
Royal College of Psychiatrists (2001). DC-LD (Diagnostic Criteria for Psychiatric Disorders for Use with Adults with Learning Disabilities/Mental Retardation). Royal College of Psychiatrists Occasional Paper OP48. Gaskell, London.
The format and extent of an assessment will depend on the nature of the presenting problem. The following scheme is taken from the book by Graham (1999), which should be consulted for further information. Graham suggests that clinicians with little time available should concentrate on the items in bold type
1 Nature and severity of presenting problem(s). Frequency. Situations in which it occurs. Provoking and ameliorating factors. Stresses thought by parents to be important.
2 Presence of other current problems or complaints.
(a) Physical. Headaches, stomach ache. Hearing, vision. Seizures, faints, or other types of attacks.
(b) Eating, sleeping, or elimination problems.
(c) Relationship with parents and siblings. Affection, compliance.
(d) Relationships with other children. Special friends.
(e) Level of activity, attention span, concentration.
(f) Mood, energy level, sadness, misery,
(g) Response to frustration. Temper tantrums.
(h) Antisocial behaviour. Aggression, stealing, truancy.
(i) Educational attainments, attitude to school attendance.
(j) Sexual interest and behaviour.
(k) Any other symptoms, tics, etc.
3 Current level of development.
(a) Language: comprehension, complexity of speech.
(b) Spatial ability.
(c) Motor coordination, clumsiness.
4 Family structure.
(a) Parents. Ages, occupations. Current physical and emotional state. History of physical or psychiatric disorder. Whereabouts of grandparents.
(b) Siblings. Ages, presence of problems.
(c) Home circumstances: sleeping arrangements.
5 Family function.
(a) Quality of parental relationship. Mutual affection. Capacity to communicate about and resolve problems. Sharing of attitudes over child’s problems.
(b) Quality of parent-child relationship. Positive interaction: mutual enjoyment. Parental level of criticism, hostility, rejection.
(c) Sibling relationships.
(d) Overall pattern of family relationships. Alliance, communication. Exclusion, scapegoating. Intergenerational confusion.
6 Personal history.
(a) Pregnancy complications. Medication. Infectious fevers.
(b) Delivery and state at birth. Birth weight and gestation. Need for special care after birth.
(c) Early mother-child relationship. Post-partum maternal depression. Early feeding patterns.
(d) Early temperamental characteristics. Easy or difficult, irregular, restless baby and toddler.
(e) Milestones. Obtain exact details only if outside range of normal.
(f) Past illnesses and injuries. Hospitalizations.
(g) Separations lasting a week or more. Nature of substitute care.
(h) Schooling history. Ease of attendance. Educational progress.
7 Observation of a child’s behaviour and emotional state.
(a) Appearance. Signs of dysmorphism. Nutritional state. Evidence of neglect, bruising, etc.
(b) Activity level. Involuntary movements. Capacity to concentrate.
(c) Mood. Expression of signs of sadness, misery, anxiety, tension.
(d) Rapport, capacity to relate to clinician. Eye contact. Spontaneous talk. Inhibition and disinhibition.
(e) Relationship with parents. Affection shown. Resentment. Ease of separation
(f) Habits and mannerisms.
(g) Presence of delusions, hallucinations, thought disorder.
(h) Level of awareness. Evidence of minor epilepsy.
8 Observation of family relationships.
(a) Patterns of interaction – alliances, scapegoating.
(b) Clarity of boundaries between generations: enmeshment.
(c) Ease of communication between family members.
(d) Emotional atmosphere of family. Mutual warmth. Tension, criticism.
9 Physical examination of child.
10 Screening neurological examination.
(a) Note any facial asymmetry
(b) Eye movements. Ask the child to follow a moving finger and observe eye movement for jerkiness, incoordination.
(c) Finger-thumb apposition. Ask the child to press the tip of each finger against the thumb in rapid succession. Observe clumsiness, weakness.
(d) Copying patterns. Drawing a man.
(e) Observe grip and dexterity in drawing.
(f) Jumping up and down on the spot.
(h) Hearing. Capacity of child to repeat numbers whispered two metres behind him.