Prevalence

Anxiety ranks among the most common categories of mental disorder reported in large-scale epidemiological studies within the general population (Reference Robins and RegierRobins & Regier, 1991); Reference Jenkins, Lewis and BebbingtonJenkins, 1997). In primary care, anxiety and depression account for 80% of consultations for mental health problems (Reference CooperCooper, 1972). Untreated, they are costly to both the individual and society. Comorbidity is also a significant problem: about 75% of individuals with an anxiety disorder meet criteria for at least one comorbid psychiatric disorder (Reference Kessler, McGonagle and ZhaoKessler et al, 1994).

In people with learning disabilities anxiety disorders are well recognised (Reference Bailey and AndrewsBailey & Andrews, 2003), may be underreported (Reference Reiss, Levitan and SzyszkoReiss et al, 1982) and underdiagnosed (Reference Veerhoven and TuinierVeerhoven & Tuinier 1997). In a sample of learning-disabled people, Reference CooperCooper (1997) found higher rates of anxiety disorders in the elderly individuals than in the younger age groups. A study cohort comparing people with learning disabilities with the general population revealed significantly higher rates of phobic disorder in the former (Reference Deb, Thomas and BrightDeb et al, 2001a ). A literature review (Reference RaghavanRaghavan, 1997) revealed a similar if not higher prevalence of generalised anxiety disorder in people with learning disabilities. Significant comorbidity was also reported in a study by Reference Masi, Favilla and MucciMasi et al (2000) in learning-disabled adolescents. Anxiety disorders were identified as more prevalent in individuals with self-injurious behaviour than in those without such behaviour (Reference Moss, Emerson and KiernanMoss et al, 2000).

Diagnosis and classification

Anxiety disorders include panic disorder, agoraphobia, specific phobias, generalised anxiety disorder, social phobia, obsessive–compulsive disorder, and acute and post-traumatic stress disorders (PTSD). Accurate diagnosis is central to the effective management of these conditions (Box 1). Frequently, comorbid disorders such as depression can make the presentation and diagnosis confusing, even in the general population.

Reference SovnerSovner (1986) highlighted four factors reflecting the profound biopsychosocial effects of learning disability that may influence the diagnostic process:

1. • intellectual distortion – emotional symptoms may be difficult to elicit because of deficits in abstract thinking and in receptive and expressive language skills; for example the phrase ‘butterflies in the stomach’ might not be understood;

2. • psychosocial masking – limited social experiences can influence the content of psychiatric symptoms; for example mania may present as a grandiose belief that the individual can drive a car;

3. • cognitive disintegration – a decreased ability to tolerate stress can lead to anxiety-induced decompensation (sometimes misinterpreted as psychosis);

4. • baseline exaggeration – the severity or frequency of chronic maladaptive behaviour may increase after onset of psychiatric illness.

Another factor that may contribute to difficulties experienced by clinicians is diagnostic overshadowing, a tendency in the clinician to overlook symptoms of mental illness, attributing them to learning disability (Reference Reiss, Levitan and SzyszkoReiss et al, 1982).

In people with learning disabilities, the clinical utility of the ICD–10 and DSM– IV–TR in diagnosing anxiety disorders is limited (Reference Ruedrich and DesNoyers HurleyRuedrich et al, 2001; Reference Cooray, Cooper, Gabriel, Fletcher, Loschen and StavrakakiCooray et al, 2005). This is because diagnostic criteria are firmly entrenched in language-based phenomenology, validated on individuals with average intellectual functioning. Currently, the evidence base relating to anxiety disorders in people with learning disabilities is poor, further compounded by difficulties in carrying out robust research (Reference Oliver, Piachaud and DoneOliver et al, 2003). Most studies use some form of modified criteria, with a resultant lack of consistency.

Endeavours to improve diagnostic practice have led to the development of guidelines (Reference Rush and FrancesRush & Frances, 2000; Reference Deb, Matthews and HoltDeb et al, 2001b ) and a number of informant and self-report assessment instruments of psychopathology, some of which are listed in Box 2. However, the reliability of these instruments is variable. Reference Costello, Moss and ProsserCostello et al (1997) reported that the greatest unreliability when applying the PAS-ADD related to symptoms of anxiety.

To address the problems of classification, a new consensus-based system reflecting expert opinion, the Diagnostic Criteria for Psychiatric Disorders for Use with Adults with Learning Disabilities/Mental Retardation (DC–LD), has been developed (Royal College of Psychiatrists, 2001). This provides operationalised diagnostic criteria for psychiatric disorders for use with adults with moderate, severe or profound learning disabilities. It may also be used to complement the ICD–10 or DSM–IV–TR in adults with mild learning disabilities.

Generally, all criteria for anxiety disorders in ICD–10 or DSM–IV–TR can be applied validly and reliably in people with mild-to-moderate learning disability (Reference Masi, Brovedani and MucciMasi et al, 2002; Reference Stavrakaki, Griffiths, Stavrakaki and SummersStavrakaki, 2002). In those with severe-to-profound disability, psychiatric assessments must be modified within the context of limitations in cognitive function, using simple spoken language, pictures and sign language. Collateral information from a primary caregiver familiar with the individual is essential. The interview must be unhurried, allowing sufficient time to give an account of events. Questions and responses may need to be repeated and rechecked. People with learning disabilities are suggestible and when presented with a choice of alternatives may agree or repeat the last words of the questionner's sentence. Consequently, leading questions must be avoided.

Effects of learning disability on the presentation of the clinical features of anxiety

The clinical features of anxiety have cognitive, physiological, psychological and behavioural components. Psychological and cognitive elements may present as fearful anticipation, irritability, concentration and memory problems, repetitive worrying thoughts, fear and, in extreme instances, fully fledged panic. Physiological manifestations include dry mouth, difficulty in swallowing, flushing, sweating, pallor, palpitations, tremor, hyperventilation, chest pain/tightness, headache, backache, fatigue, muscle tension, diarrhoea, increased urinary frequency, paraesthesia, heightened startle response and insomnia. Avoidance is a common behavioural manifestation of anxiety. Chronologically, anxiety can be episodic, continuous or stress related.

Descriptions of key diagnostic concepts of anxiety require a certain level of IQ and linguistic skills, particularly with relation to more complex subjective cognitive phenomena. Reference Matson, Smiroldo and HamiltonMatson et al, 1997 concluded that when anxiety cannot be expressed, especially in people with more severe degrees of learning disability, it might manifest as a behavioural disorder. However, this may be non-specific and may be a reflection of other triggers such as the environment. It is important to distinguish between behavioural disorders and abnormal behaviours that are the result of an underlying mental illness. In diagnosising anxiety, Reference Khreim and MikkelsonKhreim & Mikkelson (1997) highlighted the need to place relatively greater emphasis on phenomena such as agitation, screaming, crying, withdrawal, regressive/clingy behaviour or freezing, all of which could be interpreted as manifestations of fear.

In people with severe and profound learning disability, subjective elements of the diagnostic criteria for anxiety are difficult, if not impossible, to apply. The clinician must therefore rely on signs (observed behaviours) rather than on self-reported distress and on the diagnosis postulated from observations made by primary caregivers. The application of objective equivalents in lieu of subjective criteria, as well as unofficial pragmatic modifications to the DSM and ICD classificatory systems, may be justifiable in such instances. This has prompted clinicians to interpret diagnostic criteria in terms of behavioral correlates that reflect the verbal components of the relevant anxiety disorders (Table 1).

Table 1

Behavioural correlates of anxiety symptoms in learning disability

Anxiety symptom	Behavioural correlate
Dry mouth	Increased drinking
Sensations of shortness of breath	Hyperventilation
Sensations of anxiety	Signs of increased arousal (shortness of breath; increased pulse rate); irritability; anger; sweating; self-injurious behaviour; avoidance behaviour
Panic	Tremulousness with excessive motor activity, agitation and or aggression (Reference Stavrakaki, Griffiths, Stavrakaki and SummersStavrakaki, 2002)

These issues might best be addressed by the official modification of the DSM and ICD diagnostic criteria for anxiety to tailor them to adults with learning disabilities, as has already been done for the child and adolescent population.

Risk factors

People with learning disabilities frequently contend with a lifetime of adversity, inadequate social supports and poor coping skills. These factors contribute to increased vulnerability to stressful life events, which may trigger anxiety disorders. Reference Kessler, McGonagle and ZhaoKessler et al (1994) reported that all types of mental disorder, including anxiety, decline with increasing educational level. Current psychological models of anxiety tend to incorporate the role of the individual's vulnerability, which includes both genetic (Reference Smoller and TsuangSmoller & Tsuang, 1998; Kendler et al, 2001) and acquired predispositions (Reference Coplan, Pine and PappCoplan et al, 1997). Some genetic causes of learning disability have associations with anxiety, for example: fragile-X syndrome is associated with social anxiety disorder; Rubinstein–Taybi and Prader–Willi syndromes with obsessive–compulsive disorder (Reference Levitas and ReidLevitas & Reid, 1998); and Williams syndrome with anxiety (Reference Einfeld, Tonge and ReesEinfeld et al, 2001) and phobias (Reference DykensDykens, 2003). Reference Hyman, Oliver and HallHyman et al (2002) noted significantly high compulsive behaviour in Cornelia de Lange syndrome.

Studies on types of fear reported in this population demonstrate similarities between children and adults of equivalent mental age, highlighting the developmental perspective (Reference SternlichtSternlicht, 1979; Reference Duff, La Rocca and LizzetDuff, 1981; Reference Pickersgill, Valentine and MayPickersgill et al, 1994). For example individuals with moderate learning disability experience fears of: animals, thunder and ghosts (preoperational thinking), and physical injuries (concrete operational), mirroring normal Piagetian transition in non-learning disabled children. However, in childhood, anxieties and phobias might also occur as transient phenomena, integral to normal early development.

The psychological basis underpinning anxiety includes psychodynamic (anxiety perceived as an expression of unresolved conflict), cognitive (role of individual's perceptions of stressful events in aetiology of anxiety) and behavioural (role of learning, e.g. through classical conditioning and vicarious or observational learning) theories. Reference Ingram, Miranda and SegalIngram et al (1998) reported that people with anxiety frequently have negative cognitions.

Treatment

The treatment for anxiety disorders in people with learning disabilities broadly parallels that in the rest of the population (Box 3). A range of effective interventions is available (Reference StavrakakiStavrakaki, 1997), including medication (Kapczinski et al, 2004), psychological therapies (reassurance, counselling, anxiety management such as relaxation training, anger management and self-help such as biblio-therapy). Desensitisation and exposure therapy are effective management strategies in obsessive–compulsive disorder and social phobia. Some studies suggest that optimum results are achieved by combining psychological and pharmacological interventions (Reference Fineberg and DrummondFineberg & Drummond, 1995; Reference KandelKandel, 1999). Behavioural therapy and cognitive therapy alone or in combination have demonstrated clear experimental evidence of efficacy in the treatment of anxiety disorders (Reference MichelsMichels, 1997). Involving affected individuals in an effective partnership with healthcare professionals and using comprehensible and clear communication both improve outcomes (National Institute for Clinical Excellence, 2004).

In people with mild or borderline learning disability and anxiety disorders, evidence based on case studies demonstrates the effectiveness of cognitive–behavioural therapy (Reference Lindsay, Neilson, Lawrenson, Stenfert Kroese, Dagnan and LoumidesLindsay et al, 1997; Reference LindsayLindsay, 1999). The core principles of cognitive therapy may require modification to meet the abilities of the individual. Evidence relating to the long-term outcome of these interventions is unavailable, although they are likely to be beneficial.

Training and education in relaxation techniques is also helpful for those with mild, moderate or severe learning disability. Reference Martin, Gaffan and WilliamsMartin et al (1998) reported a successful outcome with relation to achieving relaxation in individuals with severe-to-profound learning disability using multisensory stimulation (Snoezelen environment).

The pharmacological treatment of anxiety, targeted at achieving maximum gains from the lowest effective dose and with minimum adverse effects include selective serotonin reuptake inhibitors (SSRIs), serotonin noradrenalin reuptake inhibitors (SNRIs), buspirone, beta-blockers, benzodiazepines and tricyclic antidepressants. People with learning disabilities may not be able to report adverse effects. Any resultant impairment of cognitive and psycho-motor abilities may have profound implications for behaviour and general functioning.

In view of their potential adverse effects benzodiazepines should be considered only for short-term (no more than 4 weeks) treatment of acute, disabling anxiety which is causing significant distress, while medium- or long-term strategies are instituted. A minority with intractable anxiety may benefit from long-term treatment, which should not be denied (Royal College of Psychiatrists, 1997).

In generalised anxiety disorder, obsessive–compulsive disorder, panic disorder, PTSD and social phobia, SSRIs may be used as first-line treatment. Treatment with SNRIs such as venlafaxine, which is effective in generalised anxiety disorder, should be supervised by specialist mental health medical practitioners. Tricyclics may be used as second-line intervention for all of these conditions with the exception of social phobia. Other pharmacological treatments with a weaker evidence base or which are less well tolerated include buspirone (generalised anxiety disorder, obsessive–compulsive disorder) and antipsychotics (quetiapine or ris-peridone as antidepressant augmentation for obsessive–compulsive disorder). The choice of treatment ultimately should be a consequence of the assessment process and shared decision-making, with emphasis on safety, tolerability and the patient's preferences within the context of best available evidence.

Key points

Box 4 summarises key learning points to be taken from this article.

MCQs

1. 1 With regard to people with learning disabilities:

   1. a a diagnosis of learning disability is dependent on significantly sub-average IQ and associated deficits in adaptive behaviour with onset occurring before 18 years of age

   2. b the prevalence of learning disability in the general population is 0.2%

   3. c mental health problems are less common than in the general population

   4. d mental health problems always present as challenging behaviour

   5. e the philosophy of normalisation supports people with learning disabilities accessing generic health services.

2. 2 The following contribute to difficulties in psychiatric diagnosis in learning disability:

   1. a diagnostic overshadowing

   2. b limitations in the patient's linguistic skills

   3. c the patient's suggestibility

   4. d limitations in the patient's social experience

   5. e absence of collateral information.

3. 3 Anxiety disorders in people with learning disabilities:

   1. a are more common than in the general population

   2. b are underdiagnosed in comparison with the general population

   3. c are less likely to be comorbid with other psychiatric disorders than in the general population

   4. d can only be diagnosed using modified diagnostic criteria

   5. e do not respond to psychological treatments.

4. 4 Anxiety is a common association in the following disorders:

   1. a fragile-X syndrome

   2. b Downs syndrome

   3. c autistic-spectrum disorder

   4. d Williams syndrome

   5. e Angelmans syndrome.

5. 5 The following are features of severe anxiety:

   1. a palpitations

   2. b disorientation in place

   3. c paraesthesia

   4. d visual hallucinations

   5. e obsessional symptoms.

MCQ answers

1		2		3		4		5
a	T	a	T	a	T	a	T	a	T
b	F	b	T	b	T	b	F	b	F
c	F	c	T	c	F	c	T	c	T
d	F	d	T	d	F	d	T	d	F
e	T	e	T	e	F	e	F	e	T