Boundaries of a syndrome

Many psychiatrists will rarely encounter a patient with true delusional disorder. It is a secretive condition and most people with it manage to avoid coming to the attention of services. Although this suggests a degree of insight or mindfulness, those who do present have often come into conflict with those around them on the basis of their incorrigible beliefs. The rarity of such patients in clinic practice is often compensated for by the strangeness of their circumstances, making them common as subjects for case presentations and curiosities in journals.

Delusional disorders are difficult and unrewarding to study. Individuals are reluctant to cooperate with treatment, often fail to take medication and can be frustratingly garrulous during therapy sessions. They offer endless evidence to support their beliefs while creating ever more elaborate ways of refuting evidence against them through appeals to coincidence, misunderstanding or alternative interpretations of the ‘facts’. As a result, and despite limited research evidence, individuals with the disorder have continued to be classified on the basis of delusional content, derived from the many early eponymous ‘syndromes’ (see Reference Enoch and TrethowanEnoch 1991), and are placed within schizophrenia spectrum disorders.

Both DSM-IV and ICD-10 (World Health Organization 1992) agree on the essential characteristics of delusional disorder: the presence of persistent delusions, independent of any transient mood disorder and not fitting criteria for schizophrenia. There are, however, notable differences between ICD and DSM criteria: DSM requires 1 month of stable delusions, whereas ICD requires 3 months; ICD will allow transitory hallucinations in any modality (including auditory but not ‘third person’ or ‘running commentary’), whereas DSM will allow only tactile and olfactory hallucinations. In the proposals for DSM-5 these are unchanged, although the confusing subjectivity in deciding whether the behaviour is ‘non-bizarre’ has been removed. The only significant change proposed in DSM-5 is to distance delusional disorders further from a promising line of evidence that may link them to obsessive spectrum disorders such as body dysmorphic disorder by specifying that delusional disorder cannot be diagnosed if ‘the disturbance is not better accounted for by another mental disorder such as body dysmorphic disorder or obsessive compulsive disorder’ (DSM-5 Task Force 2011).

In fact, unlike the other disorders in the schizophrenia spectrum, delusional disorders are not associated with symptoms of thought alienation, passivity and negativity. Patients with these symptoms cannot, by definition, be diagnosed with delusional disorder. The limited work on the diagnostic relationships of delusional disorder include a study of monozygotic/dizygotic concordance rates for schizophrenia spectrum disorders, which found that delusional disorder is unlikely to be related to them (Reference Farmer, McGuffin and GottesmanFarmer 1987). This is supported by more recent genetic research evidence, which suggests that delusional disorder has no relation to the dopamine D₁ receptor gene (Reference Debnath, Das and BeraDebnath 2010). There is a school of thought that considers delusional disorder to relate more naturally to a currently disparate group of disorders that contain both obsessional and delusional components (Reference Fear, Sharp and HealyFear 2000; Reference O'Dwyer and MarksO'Dwyer 2000; see also Reference HollanderHollander (1993) and Reference Hollander, Zohar and SirovatkaHollander et al (2011) for detailed commentary).

Constitutional vulnerabilities

Kraepelin distinguished between dementia praecox (later renamed schizophrenia) and paranoia (later called delusional disorder) on the basis that the former comprised incoherent delusions in a disintegrating personality, whereas in the latter the personality was intact and the delusions coherent. Reference JaspersJaspers (1923/1946) subsequently made a distinction between the true delusions of schizophrenia, ‘which go back to primary pathological experiences as their source, and which demand for their explanation a change in the personality’ (p. 106), and the term delusion-like experiences which is ‘reserved by us for those so-called “delusions” that emerge comprehensibly from other psychic events and can be traced back psychologically to certain affects, drives, desires and fears’ (pp. 106–107). Sérieux and Capgras postulated a hypertrophy of attention in which the individual focuses on particular issues to the exclusion of others, recalling the 19th-century concepts of idées fixes (for a review, see Reference Fear, McMonagle and HealyFear et al 1998). Reference KaffmanKaffman (1981) investigated this with people with delusions, finding true experiences at the root of delusion-like experiences.

Over the past two decades, these theories have been supported by data from studies of attributional, attentional and reasoning processes, including ‘hypertrophy of attention’ in such individuals (Reference Fear, McMonagle and HealyFear 1998). The Australian National Survey of Mental Health and Wellbeing found that delusion-like experience occurred in approximately 8% of their study population (n = 8841) and was more common in individuals who were under situations of ‘non-specific psychological stress [but] otherwise well’ (Reference Saha, Scott and VargheseSaha 2011). It has since been found that there is an association between post-traumatic stress disorder (PTSD), trauma and delusion-like experience (Reference Scott, Chant and AndrewsScott 2007), with a positive correlation between traumatisation and intensity of delusional ideation. Negative cognitions of self were associated with level of delusional ideation, preoccupation and distress, whereas negative cognitions about the world were associated with paranoia (Reference Calvert, Larkin and Jellicoe-JonesCalvert 2008). These findings would support a model of delusion-like experiences arising from a ‘pathology of attention’ in which individuals are sensitised into a particular belief system by a real experience, subsequently attending selectively to perceptions and experiences that support those beliefs through a mechanism that might have parallels in the re-experiencing cues of patients with PTSD. This is supported by findings of the centrality of self within the discourse of individuals with delusional disorder (Reference Noel-Jorand, Reinert and GiudicelliNoel-Jorand 2004) and the feature of self-reference found in 40% of a sample of 370 people with the disorder (Reference De Portugal, Gonzalez and HaroDe Portugal 2008).

It seems likely that delusional disorder, in its pure form, is a condition based on constitutional vulnerabilities that are part of an intact personality. Under variable levels of psychological stress, vulnerable individuals develop delusion-like responses which offer scenarios that allow them to manage the stress. The core cognitive bias is a pathology of attention in which a preoccupation with an idea is supported by cues, codes, checking and situational expression. Sadly, the lack of rigour in DSM's approach to delusional disorder has allowed a large variety of case reports claiming to describe delusional disorder where the delusions are clearly secondary to other pathology, such as multiple sclerosis (Reference Muzyk, Christopher and GaglardiMuzyk 2010), mania (Reference Vicens, Sarro and McKennaVicens 2011) and Wilson's disease with alcoholism (Reference Spyridi, Diakogiannis and MichaelidesSpyridi 2008); it has, in turn, ignored the clear links to obsessive spectrum disorders. The clear parallels between obsessional and delusional forms of jealousy, body dysmorphia, somatoform disorders and even anorexia nervosa are discussed later in this article.

Recent reviews of two specific types of delusional disorder have proposed the distinction of ‘primary’ delusional disorder, where the diagnosis can only be made in the absence of other (psycho) pathology, and ‘secondary’ delusional disorder, where the primary pathology may be another psychiatric disorder, organic brain disorder or induced by psychoactive substances (Box 1) (Reference KellyKelly 2005; Reference Lepping, Russell and FreudenmannLepping 2007). For clarity, this review has, where possible, considered only treatment reports relating to the treatment of primary delusional disorder.

BOX 1 Medical, neuropsychiatric and other associations with delusional disorder

Syndromes	Medications and intoxicants	Other associations
• Dyslexia • Intellectual vtual disability • Fragile-X syndrome • Head injury • Cerebral ischaemia • Meningioma • Epilepsy • Dementia (any cause) • HIV • Asperger syndrome • Wilson's disease • Parkinson's disease	• Alcohol • Anovulants • Steroids • Methylphenidate • Venlafaxine • Radiotherapy • Chemotherapy	• Pregnancy/childbirth

(After Reference KellyKelly 2005)

Epidemiology

DSM-IV estimates the prevalence of delusional disorder in the USA to be about 0.03, suggesting that it accounts for 1–2% of hospital admissions (American Psychiatric Association 1994: p. 299). Subsequent large population studies have shown a prevalence of 0.18% in a Finnish sample aged over 30 (Reference Suvisaari, Pera and SaarniSuvisaari 2009), which equates with a finding of 2% in 378 982 out-patients and in-patients at a hospital in Thailand between 2003 and 2007 (Reference KosiyakulKosiyakul 2008). In the UK, of 227 patients presenting to an early intervention service over a 3-year period, 7% were found to have delusional disorder (Reference Proctor, Mitford and PaxtonProctor 2004). By contrast, the 467 out-patients with DSM-IV delusional disorder found in a case-register study in a south Barcelona population of 607 494 (0.08%) indicate the elusive nature of the condition. The most frequent subtypes were persecutory (48%), jealous (11%), mixed (11%) and somatic (5%); 23% were classified as ‘not otherwise specified’. Nearly 9% had a family history of schizophrenia and 42% a comorbid Axis II diagnosis, with paranoid personality disorder predominating (Reference De Portugal, Gonzalez and HaroDe Portugal 2008).

Two studies have looked at gender differences, finding a female:male ratio of 1.6:1 (Reference De Portugal, Gonzalez and MiriamDe Portugal 2010) and 1:1 (Reference Wustmann, Pillmann and MarnerosWustmann 2011), the difference between studies probably reflecting sample sizes. Men had more schizoid/schizotypal premorbid personality features, were younger at disorder onset, showed poorer long-term social functioning and were more likely to have the diagnosis changed later to schizophrenia or schizoaffective disorder. Women showed poorer initial social functioning, but regained functioning through their better engagement with therapeutic interventions; they were more likely to receive medication but their disorder was less likely to remit, although they were more able to compensate and live independently despite the delusions (Reference De Portugal, Gonzalez and MiriamDe Portugal 2010; Reference Wustmann, Pillmann and MarnerosWustmann 2011).

Diagnosis

Interviewing a patient with possible delusional disorder poses significant challenges. The patient rarely attends assessment by choice and may be encountered only when facing criminal charges or significant domestic difficulties as a result of their beliefs. Faced with someone who is, in all respects (other than their delusional system) entirely ‘normal’ and will probably be socially skilled, it may be difficult to understand where the delusional symptomatology lies. It is entirely plausible that their partner may be unfaithful; they may try to convince you that the celebrity they have been contacting has valued their contact and come armed with polite messages from them to suggest that this is the case; it is conceivable that the authorities have behaved prejudicially towards them or that the doctor missed that one diagnostic test that would have clinched the diagnosis. Interviews are likely to be a time-consuming mixture of standard psychiatric history-taking and dancing around an area that the patient is reluctant to discuss. The process may be time-consuming and is unlikely to be productive in the pressured environment of a standard psychiatric clinic.

Pharmacotherapy

Cognitive and behavioural therapy

The work of a number of groups during the 1990s focused on the management of individual psychotic symptoms, such as delusions and hallucinations, in isolation from their underlying conditions (e.g. Reference Rankin and O'CarrollRankin 1995; Reference Sharp, Fear and HealySharp 1997; Reference Garety and FreemanGarety 1999; Reference Bentall, Corcoran and HowardBentall 2001). Although these could be criticised for missing the point that associated affect and psychotic experiences can have a profound effect in maintaining an individual's delusional system, they were invaluable in providing an evidence base for exploring and challenging a patient's abnormal beliefs. Previously these had been avoided, either through the mistaken view that exploring the origins of beliefs provided validation and collusion or through the misunderstanding that all delusions were, by their nature, un-understandable. There is now overwhelming evidence that delusions can and do respond to lengthy and intensive individual cognitive therapy, but few study samples comprising only patients with delusional disorder (for a review, see Reference Freeman, Bentall and GaretyFreeman 2008).

Aside from single case reports, two studies have undertaken work with patients with delusional disorder. Reference Sharp, Fear and WilliamsSharp et al (1996) reported on a series of six patients, three of whom responded to cognitive therapy. The key factor predicting response was a reduction in conviction from 100% during the baseline phase of information gathering and before therapy actually started. Conviction was significantly associated with belief maintenance factors in all three individuals but there were no consistent associations. Affect associated with the belief, willingness to talk to others about the belief, negative behaviours and insight were associated with conviction in some, but not all, patients; preoccupation and acting on the belief varied systematically independently of belief conviction.

More recently, a Canadian group (Reference O'Connor, Stip and PelissierO'Connor 2007) has compared cognitive–behavioural therapy (CBT) v. attention placebo control in 24 patients with delusional disorder over a 24-week treatment period. Eleven patients completed the CBT treatment, whereas half dropped out of the attention placebo control group. In addition to a lower drop-out rate from therapy, CBT produced a greater reduction in affect relating to belief, strength of conviction and positive action on belief subscales of the Maudsley Assessment of Delusions Schedule. Although the delusions were not abolished by CBT, the positive changes provide a strong basis for further work on managing the individual's response to their delusional systems, improving social inclusion and reducing risk.

Electroconvulsive therapy

Although Reference FinkFink (1995) considered electroconvulsive therapy (ECT) to be an ‘antidelusional agent’, there have been few reports of its use and the reported benefits may have resulted from the resolution of underlying depression. A case report of somatic delusional disorder responding to ECT did not sufficiently exclude an affective component (Reference Ota, Mizukami and KatanoOta 2003). Furthermore, given that the response of psychotic phenomena in schizophrenia to ECT is not long lasting, there would appear to be no indication for the use of ECT in delusional disorder (for a review, see Reference Fear and ScottFear 2005).

The spectrum of disorders of attention bias

There are a number of conditions that involve a preoccupation with a single aspect of an individual's experience, including: morbid jealousy, where the core issue is a partner's fidelity; body dysmorphic disorder, where the focus is on appearance; somatoform disorders, involving illness; and anorexia nervosa, where the issue is body image. Each of these has a fundamental issue of attention bias and can show a range of pathologies from obsessive preoccupation, through delusion-like ideas, to true delusion. In the case of anorexia nervosa, it is not usually accepted that the incorrigible distortion of body image represents other than an ‘overvalued idea’, although there is evidence that such ideas reach delusional proportions (Reference Steinglass, Eisen and AttiaSteinglass 2007) and respond to olanzapine treatment (Reference Dunican and DelDottoDunican 2007). Indeed, there has long been a school of thought that recognises the apparent link between conditions involving obsession and those involving delusions (Reference Fear, Sharp and HealyFear 1995). Nowhere is this better demonstrated than in morbid jealousy and its delusional version (Reference Kingham and GordonKingham 2004). A variety of mechanisms have been proposed for this, including loss of insight and resistance to obsessions, depressive change and the finding that some individuals with obsessive–compulsive disorder have similar attention and attitudinal biases to those who develop delusional disorder, a ‘delusional diathesis’ (Reference Fear, Sharp and HealyFear 2000).

The possibility that delusional disorder may arise from a similar pathology of attention to obsessive disorders offers new ground to explore in pharmacotherapy. There is considerable evidence for obsessive–compulsive disorder and related disorders, particularly body dysmorphic disorder, responding to SSRIs (National Institute for Health and Clinical Excellence 2005). Although the published reports of response of delusional disorder to these drugs are few and can be explained through comorbid affective disorder, the potential of SSRIs to improve delusional disorder is worthy of serious exploration. If the conditions are, indeed, linked through a pathology of attention, it may be worth using higher doses of SSRIs in a way which is well-evidenced for obsessive spectrum disorders.

MCQs

Select the single best option for each question stem

1. 1 One antipsychotic drug with a licence for treating at least one delusional disorder subtype is:

   1. a olanzapine

   2. b paroxetine

   3. c pimozide

   4. d flupentixol decanoate

   5. e methylphenidate.

2. 2 The following is not a DSM-IV subtype of delusional disorder:

   1. a body dysmorphic

   2. b jealous

   3. c erotomanic

   4. d grandiose

   5. e persecutory.

3. 3 When assessing a patient with suspected delusional disorder:

   1. a a police officer should usually be present

   2. b it is essential to challenge the delusional belief from the outset

   3. c the presence of first-rank symptoms confirms the diagnosis

   4. d it is important to establish a rapport based on impartiality

   5. e a family history of schizophrenia is not relevant.

4. 4 The following psychological therapy has an evidence base for treating delusional disorder:

   1. a psychodynamic

   2. b cognitive

   3. c anger management

   4. d rational emotive therapy

   5. e psychodrama.

5. 5 The following type of hallucination can occur in delusional disorder subtypes:

   1. a visual

   2. b ‘third person’ auditory

   3. c passivity experience

   4. d Capgras syndrome

   5. e tactile.

MCQ answers

1

c

2

a

3

d

4

b

5

e