Psychiatric and behaviour disorders among adult persons with intellectual disability
Anton Došen
Introduction
The behavioural and emotional difficulties that are experienced by adults with intellectual disability (ID) have been regarded for many years as manifestations of their intellectual deficits and maladaptive learning. The awareness that these persons may also suffer from mental illness was a notion that came into being in the midnineteenth century.
Nevertheless, the psychiatric problems of individuals with ID were continually ignored in the first half of the twentieth century. In the past three decades, the flourishing normalization philosophy has highlighted the psychiatric problems of this population once again and rekindled the interest of practitioners, scientists, and service providers. Systematic studies have been performed which indicate that the full spectrum of psychiatric disorders as we know them today can be identified among the persons with ID. Moreover, it is probable that they may be prone to a psychopathology that is determined by the specifics of their biological and psychosocial being.
Clinical features
Features affecting presentation
Studies indicate that the types of psychiatric symptoms and syndromes that are observed among persons with borderline and mild ID are similar to those encountered among the population in general. Amongst individuals with moderate and severe ID, however, the presentation of mental illness may be less typical, and the diagnosis more difficult to establish.
Sovner and Hurley(1) have categorized four factors which may influence the presentation of mental illness among the persons with ID: intellectual distortion (impaired ability to conceptualize feelings and to communicate them to others), psychological masking (lack of usual richness of the symptomatology found in general population), cognitive disintegration (inclination to become disorganized and to exhibit regressive behaviour), and baseline exaggeration (increase of pre-existing maladaptive behaviour by emotional stress or mental illness).
Hucker et al.(2) pointed to a generally banal symptomatology encountered among these individuals, often accompanied by regression to a child-like state of dependency and hysterical features. Behavioural disturbances were often more important than symptomatic complaints as indicators of psychiatric disorders.
Apparently, the lower the IQ, the more the symptoms of mental illness tend to lose their specificity, or take on a different meaning than is the case with the intellectually normal population. This, undoubtedly, makes it difficult to establish a confident diagnosis of mental illness in people with severe ID.(3)
The following is a concise survey of the striking clinical features of mental illness and behaviour problems as they occur among adult persons with ID.
Mental illness
(a) Psychosis
Among persons with mild ID, classical clinical features are present in psychotic states. The symptoms tend to be florid but banal. In schizophrenia, for example, there is a high incidence of delusions and hallucinations, which reflect the limited experiences, naive and wishful thinking, interests, and social horizon of the patient. Ideas, that have been influenced by radio, television, etc., are found frequently. Catatonic features with odd postures and slowness are common. Impulsive, aggressive, auto-aggressive, and bizarre behaviours may dominate the clinical picture. In the chronic-phase apathy, lack of motivation and social withdrawal are common.(4,5) Increase of ‘negative’ schizophrenic symptoms and decrease of functional abilities were observed in the group with ID when compared with the group from general population with schizophrenia.(6)
Establishing the diagnosis of schizophrenia in persons with more severe ID can be a difficult task because of verbal communicative difficulties. Reid(7) considers it to be impossible to establish such a diagnosis among persons who only communicate non-verbally. However, the problem of establishing the diagnosis does not mean that psychotic conditions do not occur in these individuals. To the contrary, it is likely that different sorts of psychosis occur in this population more frequently than in general population (see Chapter 4.5.2).
Short-term psychotic states (lasting several days or weeks), usually beginning rather suddenly after a stressful event, are found relatively often among adolescents and young adults with ID. Early Dutch psychiatric literature refers to these states as ‘debility psychosis’. The symptoms may be heterogeneous, and remission is usually complete. These persons usually revert fully to the premorbid level of functioning. However, recurrence is frequent.
Establishing the diagnosis of atypical psychosis (contrary to diagnosing schizophrenia) is, for an experienced practitioner, possible even with patients who have no language development and are at a severe level of ID. The primary symptoms are changes in interactional patterns, changes of posture and movement, odd and bizarre behaviour, disturbances of the physiological functions, expression of emotional tension (e.g. anxiety, irritability), aggression, and self-injuring behaviour.
(b) Major depression and bipolar disorders
Depressed mood and vegetative symptoms are the most striking symptoms, even though complaints of depression are not always expressed. A depressive mood often is not verbalized, particularly among individuals at a lower intelligence level, but may well be observable. Similarly, the elevation of mood in mania is usually not expressed verbally either. Atypical features such as regression to child-like dependency, incontinence, loss of social skills, and hysterical symptoms such as pseudo-fits and paralysis may mask classical symptomatology. In persons with a more severe disability, depression should be suspected where there is a change or onset of behaviour problems like stereotypic behaviour, tantrums, aggression, and self-injuring behaviour.(4,8) Catatonic features and visual hallucinations, particularly among persons at lower intelligence levels, have also been reported.(2,9,10) The atypical symptomatology among persons on lower developmental levels may require modification of standard diagnostic criteria.
Aggressive behaviour was observed in 40 per cent of the depressed subjects.(11) Self-injuring behaviour has often been reported as well.
Suicidal behaviour has hardly ever been studied in this population, and suicidality is very rare among the more severely handicapped. This symptom is, however, not rare among depressive patients at a mild level of ID.
Suicidal behaviour has hardly ever been studied in this population, and suicidality is very rare among the more severely handicapped. This symptom is, however, not rare among depressive patients at a mild level of ID.
Some investigators report the relatively frequent occurrence of rapid-cycling affective disorder,(12) particularly in persons with more severe disability. Episodes of particular mood or of an undifferentiated mood-like dysphoria or irritability have a short duration, and may be expressed in terms of days or weeks.(9) Researchers assume that these disorders, in persons with ID are often related to organic brain disorders, that is, metabolic, neuroendocrine, and other neurological disorders.
In mixed bipolar disorder, there is either the simultaneous presence of manic and depressive features, or these features follow each other rapidly. Schizoaffective psychoses are also described among these individuals.
(c) Dysthymic disorder
Dysthymia is a relatively common disorder among persons with mild and moderate ID.(9,13) Nevertheless, publications on this disorder are rare. The symptomatology includes loss of energy and interest, negative self-image, feelings of helplessness, anxiety, and significant behavioural problems such as irritability, anger, destructibility, and aggression. The disorder is often related to a specific stress, for example, termination of an affective relationship, change in the surroundings, hospitalization, etc. Chronic states, dating back to the childhood or the teens, possibly caused by chronic overdemanding, social deprivation, or repeated abuse, may be interrupted by episodes of major depression, usually elicited by acute stress (so-called ‘double depression’, see Chapter 4.5.3). Došen and co-workers found this disorder relatively frequent in adolescents and young adults with ID and called it ‘developmental depression’.(10, 14) Social interactional problems, poor social skills, and difficulties related to emotional development are considered to be predisposing factors for this disorder.(14)
(d) Anxiety disorders
The most commonly reported anxiety disorders are simple phobia, social phobia, and generalized anxiety disorder.(4) It seems that adults with ID have fears similar to those of children who are at the same mental age: fear of separation, fear of natural events, fear of injury, and fear of animals. The anxieties and fears are probably related to the traumatic events and cumulative failure experiences that these persons have. The presentation may be through behaviour problems, irritability, problems with sleeping, or somatic complaints.(5) In a panic disorder, a sudden onset, blackouts, aggression, sweating, and shaking may be observable. The obsessive-compulsive disorder may be difficult to diagnose in persons with ID because they do not resist against such feelings and the anxiety is often absent. According to some authors,(4) the diagnosis can be established with the emphasis being on the externally observable behavioural components, despite of absence of some internal states like anxiety and resistance. Post-traumatic stress disorder is likely to occur in this population, following relatively less severe stress than among general population. The diagnosis in those who are unable to communicate their experiences should be based on changes in a person’s behaviour, mood, and level of functioning following a traumatic event.(4)
(e) Autism spectrum disorder
Autism spectrum disorders have been estimated to be present in 10 per cent of persons with mild ID and 40 per cent of those with severe ID, and account for a large proportion of behaviour disorders. It also appears that mental illness occurs frequently as a secondary disorder among these individuals.
A possible relationship between affective illness and pervasive developmental disorder has been suggested by various investigators(12); however, this phenomenon has been examined insufficiently and is clearly an area that future research can be directed to. In clinical practice, we have encountered a number of cases of pervasive developmental disorder together with secondary atypical psychosis. Inexperienced practitioners are inclined to diagnose schizophrenia in such cases. However, thorough developmental history will reveal sufficient information to make diagnostic differentiation possible. Other problematic behaviours such as anxious, aggressive, auto-aggressive, or disruptive behaviour are frequently found among persons who have an autism spectrum disorder and ID.(15) In our opinion, these behaviours should be seen as being secondary disorders instead of as part of the autistic disorder.
(f) Dementia
In individuals with dementia, the typical features such as memory impairment, personality change, loss of social skills, and deterioration in habits are always present. Behavioural problems may be the most obvious manifestation. Nocturnal confusion, transient psychotic episodes, and late-onset epilepsy should always alert one to the possibility of a dementing illness in the ageing person with ID. Memory loss is generally difficult to identify in the early stages, but becomes more obvious as the illness progresses. Medical risk factors include a history of hypertension, ischaemic episodes, neurological symptoms, organic brain damage, and a family history of dementia. Dementia Alzheimer type in persons with Down syndrome presents a similar picture and is usually associated with generalized premature ageing.
Behaviour disorders—challenging behaviour
Behaviour disorders including aggression, self-injury, destructiveness, and disruptive, maladaptive, and antisocial behaviour occur commonly among persons with ID. Such behaviour has recently been called challenging behaviour, which emphasizes the need for appropriate care and supervision. These disorders are usually associated with severe ID, but can also occur in individuals who are at a moderate and mild level of ID.
Various attempts have been made to distinguish between behaviour disorders and psychiatric illness in these individuals. Gardner and co-workers(16) have proposed a bio-psycho-social diagnostic approach, which takes account of the multiple factors underlying and maintaining the behaviour disturbances of a particular individual. They point out that behaviour disorders with a neuropsychiatric and organic basis can still acquire a functional component if they are being reinforced by the environment or are of value to the individual. Another approach is from the developmental perspective,(3,17) viewing behaviour disorders as the result of a lack of real understanding of the person’s developmental aspects and interactional problems.
(a) Aggressive behaviour
Aggressive behaviour is a common problem among persons with ID. The symptom of aggression is often a feature of the psychosis, depression, or antisocial personality disorder, and is often described in genetic disorders such as the fragile X, Prader-Willi, and
Klinefelter syndromes. Learned aggression through the imitation of aggressive models or as a function of communication is also found relatively frequently among people with ID.
Klinefelter syndromes. Learned aggression through the imitation of aggressive models or as a function of communication is also found relatively frequently among people with ID.
(b) Self-injurious behaviour
Self-injurious behaviour occurs more often among persons with moderate and severe ID (IQ < 50), beginning sometimes in toddler age and most frequently between the ages of 10 and 20. The occurrence of self-injurious behaviour is related to genetic and organic disturbances and adverse environmental and development conditions. Certain psychiatric disorders such as depression and psychosis may also elicit self-injurious behaviour.
(c) Offending behaviour
Owing to their behaviour problems, these individuals may become involved in activities, that bring them into conflict with the law. Insufficient understanding of their problems and needs may result in their not receiving the appropriate support from the social services. The typical offender with ID is, according to Day,(18) a young male functioning in the mild to borderline intellectual range, from a poor urban environment, with a history of psychosocial deprivation, behaviour problems, and personality disorder. The most common offences are acquisitive and technical, but sex offences and arson are considerably overrepresented.
Personality disorders
Various investigators have reported personality disorders among persons with ID.(19,20) The relevance of the concept of personality disorder, in particular with regard to the persons with more severe ID, has been questioned by a number of investigators. Apparently, in these persons, besides the problem of personality disorders, there is a problem of personality development. Zigler and colleagues(21) have explored personality traits thought to be particularly salient in determining the behaviour of individuals with ID. Levitas and Gilson(22) have stressed the importance of a crisis period during the process of personality development and the related psychosocial aspects. Other developmentally oriented authors(14,23) make a link between, on the one hand, the problematic processing of particular phase-specific aspects of emotional development and ego structuring, such as the achievement of secure attachment, an intercompetitive separation-individuation process, and the establishing of ego functions, and, on the other hand, the increased vulnerability of these individuals to particular psychiatric disorders such as depression, social withdrawal, disruptive behaviours, etc. Classification of personality problems within the existing diagnostic categories for personality disorders in general population is questionable and requires modification of particular diagnostic criteria.(4, 5) It is unlikely that personality disorders could be diagnosed in persons with severe/profound ID.
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