Delusional Disorder

Delusional disorder is an illness characterized by at least 1 month of delusions but no other psychotic symptoms, according to the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR). ^[1] Delusions are false beliefs based on incorrect inference about external reality that persist despite the evidence to the contrary; these beliefs are not ordinarily accepted by other members of the person's culture or subculture. Delusions can be characterized as persecutory (i.e., belief that one is going to be harmed by an individual, organization or group), referential (i.e., belief that gestures, comments, or environmental cues are directed at oneself), grandiose (i.e., belief that the individual has exceptional abilities, wealth, or fame), erotomanic (i.e., a false belief that another individual is in love with him/her), nihilistic (i.e., a conviction that a major catastrophe will occur), or somatic (i.e., beliefs focused on bodily function or sensation). Because cognitive organization and reality testing are otherwise intact in delusional disorder, it has been described in the literature as "partial psychosis." ^[2]

Nonbizarre delusions are about situations that could occur in real life, such as being followed, being loved, having an infection, and being deceived by one's spouse. Bizarre delusions are clearly implausible and reflect beliefs that would be physically impossible. Delusions that express a loss of control over mind or body are generally considered to be bizarre and include beliefs that one’s thoughts have been removed by an outside force, that alien thoughts have been put into one’s mind, or that one’s body or actions are being acted on or manipulated by an outside force. ^[1]

Making a distinction between a delusion and an overvalued idea is important, the latter representing an unreasonable belief that is not firmly held and could be subject to persuasion and/or alternative interpretation. ^[1] Additionally, personal beliefs should be evaluated with great respect to complexity of cultural and religious differences; some cultures share widely accepted beliefs that may be considered delusional in other cultures.

Unfortunately, patients with delusional disorder, by definition, do not have good insight into their pathological experiences. Interestingly, despite significant delusions, many other psychosocial abilities and other reality testing remain intact, as if the delusions are circumscribed. Indeed, this is one of the key differences between delusional disorder and other primary psychotic disorders. However, the individual may rarely seek psychiatric help, remain isolated, and may present to internists, surgeons, dermatologists, other physicians, police officers, and/or lawyers rather than psychiatrists.

Case study

Ms. K. is a 39-year-old woman who was brought to the inpatient psychiatric unit by police after being arrested for trespassing on Mr. L’s property. Upon arrival, Ms. K was adamant about being released, stating that she was simply entering her husband’s home, adamantly declaring that Mr. L was her husband. She elaborated a story about how much the two of them loved each other, when they got married, and how she was currently pregnant with his child. In actuality, Mr. L. used to be Ms. K’s boss, and had fired her because of her inappropriate romantic advances towards him several years previously. Ms. K was actually married to another man in Florida, with whom she denied any marital relationship, stating that she was kidnapped by him for 4 years, and after escaping, had come to California to be with her husband, Mr. L. Ms. K was diagnosed with delusional disorder, erotomanic type, and was started on risperidone 2 mg PO at bedtime.

Patient evaluation

Theo Manschreck ^[3] outlined 3 steps in the initial evaluation of patients who present with delusions.

First, establish whether psychopathology is present. This represents a clinical judgment that is sometimes difficult to make. Some comments that initially appear delusional may be in fact true. In contrast, some reports that initially seem believable may later be identified as delusions as the symptoms worsen, the delusions become less encapsulated (ie, begin to extend to more people or situations), and more information comes to light. The clinical judgment that delusions are present should be made after taking into account the degree of plausibility, systemization, and the possible presence of culturally sanctioned beliefs that are different from the examiner's own beliefs. Making the distinction among a true observation, a firm belief, an overvalued idea, and a delusion is sometimes a challenging task. Often, the "extremeness" and inappropriateness of the patient's behaviors associated with a given belief, rather than the simple truth or falsity of the belief itself, indicate its delusional nature. ^{[3, 4]}

The second step is determining the presence or absence of important characteristics and symptoms often associated with delusions, such as confusion, agitation, perceptual disturbances, physical symptoms, and/or prominent mood abnormalities. ^[3] Studies have shown that the most common symptoms reported in delusional disorder were self-reference (40%), irritability (30%), depressed mood (20%), and aggressiveness (15%). ^[5]

The third step is to present a systematic differential diagnosis. A thorough history, mental status examination, and laboratory/radiologic evaluation should be performed to rule out other systemic medical and psychiatric conditions that commonly present with delusions. Other, non-psychiatric CNS illnesses are high on the differential diagnosis of any psychotic disorder; this is especially so if the onset of delusional disorder in patients is older than the typical age of onset of schizophrenia. Delusional disorder in this sense should be seen as a diagnosis of exclusion. ^[3]

Diagnostic criteria (DSM-5-TR)

The specific DSM-5-TR criteria for delusional disorder are as follows: ^[1]

• Presence of one or more delusions with a duration of one month or longer.

• The diagnostic criteria for schizophrenia has never been met. Note: Hallucinations, if present, are not prominent and are clearly thematically related to the delusional theme (e.g., the sensation of being infected with insects is associated with the delusion of infestation).

• Apart from the impact of the delusion(s) or its ramifications, patient functioning is not markedly impaired, and behavior is not obviously bizarre or odd.

• If manic and/or major depressive episodes have occurred, these have been brief relative to the duration of the delusional symptoms.

• The disturbance is not better explained by another mental disorder, such as obsessive-compulsive disorder, and is not attributable to the physiological effects of a substance or medication or another systemic medical condition.

Subtypes include erotomanic, grandiose, jealous, persecutory, somatic, mixed, and unspecified. The diagnosis is further specified “with bizarre content” when delusions are clearly implausible, not understandable, and not derived from ordinary life experiences.

The following duration specifiers apply after 1-year duration of the disorder:

• First episode, currently in acute episode

• First episode, currently in partial remission

• First episode, currently in full remission

• Multiple episodes, currently in acute episode

• Multiple episodes, currently in partial remission

• Multiple episodes, currently in full remission

• Continuous

United States statistics

The prevalence of delusional disorder in the United States is estimated in the DSM-5-TR to be around 0.02%, ^[1]  which is considerably lower than the prevalence of schizophrenia (1%) and depressive disorders (5%). ^[6] Our current understanding of the prevalance of delusional disorder is limited by sparse epidemiologic data that mostly includes individual case descriptions or small uncontrolled case studies. ^[7]

International statistics

A British study reported that of 227 patients presenting to mental health centers with a first episode of psychosis during the 3-year study period, 7% were diagnosed with persistent delusional disorder, as compared to 11% with schizophrenia and 19% with psychotic depression. ^[8]

Gender differences in incidence

The female-to-male ratio has been reported to vary from 1.18 ^[9] -3:1 ^[10] . Men are more likely than women to develop paranoid delusions; women are more likely than men to develop delusions of erotomania. ^[6] Associated factors with delusional disorder include being married, being employed, recent immigration status, low socioeconomic status, celibacy (among men), and widowhood (among women). ^{[9, 11]}

Age-related differences in incidence

The mean age of onset is 40 years and ranges from 18-90 years. ^[6] A Spanish study conducted by de Portugal et al looked at medical records of 370 people diagnosed with delusional disorder and found that the mean age in this population was 55 years, with 56.5% of the patients being female.

General considerations

The etiology of delusional disorder is unknown, and several difficulties exist in conducting research in this area:

• Patients currently diagnosed with delusional disorder may represent a heterogeneous group of patients with delusions as the predominant symptom.

• Patients often do not present for treatment, and thus do not commonly make themselves available for research studies.

• Strong indications exist that delusional disorder is a distinct condition, different from schizophrenia or depressive disorder. Naturalistic studies indicated that delusional disorder has a relatively stable course.

• The definition of this condition has changed over time and continues to be a work in progress.

Genetics

The relationship of delusional disorder to the more severe psychotic illnesses is yet unclear. According to the DSM-5-TR, on average, global function in delusional disorder is generally better than that observed in schizophrenia. Although the diagnosis of delusional disorder is generally stable over time, a proportion of affected individuals go on to develop schizophrenia. Delusional disorder has a significant familial relationship with both schizophrenia and schizotypal personality disorder. Although it can occur in younger age groups, the condition is more prevalent in older individuals. ^[1]

Biochemical factors

Biological factors may play some role in the development of delusional disorder, as delusions are associated with a wide range of nonpsychiatric medical conditions. Among patients with neurologic disorders, lesions of the basal ganglia and temporal lobe are most commonly associated with delusions. ^{[6, 12]} However, a case report of a somatic delusion involving reduplication of body parts implicated the temporal and parietal lobes, showing hypoperfusion of both regions. ^[13]

Campana et al ^[14] used eye tracking movement tests to explore the relationship between frontal lobe functions and clinical symptoms of delusional disorder. They found that compared with normal participants, patients with delusional disorder showed abnormalities of voluntary saccadic and smooth pursuit eye movements, which is also seen in schizophrenia.

Hyperdopaminergic states have been implicated in the development of delusions. Recently, Morimoto et al ^[15] reported that 13 patients with delusional disorder were reported to have increased levels of plasma homovanillic acid (HVA) (a dopamine metabolite) compared with control subjects. Patients responded well to treatment with low-dose haloperidol (average 2.7 mg/d) and showed decreased posttreatment plasma level of HVA, which correlated with the improvement of their symptoms.

The same authors reported an increased prevalence of a polymorphism at the D2 receptor gene at amino acid 311 (cysteine-for-serine substitution) among individuals with delusional disorder, particularly those with persecutory delusions. Individuals that had more TCAT repeats within the first intron of the tyrosine hydroxylase gene had higher levels of HVA, although it is unclear if the authors corrected for multiple statistical comparisons. ^[15]

Psychological factors

The fields of cognitive and experimental psychology suggest that persons with delusions selectively attend to certain information, a cognitive pattern that overlaps with hypochondriacal patients. ^[16] They make conclusions based on insufficient information, attribute negative events to external personal causes, and have difficulty in envisaging others’ intentions and motivations. ^[4]

Conway et al ^[17] reported that patients with delusional disorder made probability decisions based on fewer data compared with normal controls. Despite using fewer data, they were similarly certain as controls regarding the accuracy of their decisions.

Two neuropsychological models proposed for schizophrenia may also have some validity in delusional disorder. A cognitive bias model (CBM) proposes that paranoia is a defense against thoughts that threaten the idealized self, to protect a fragile self-esteem. Positive events are attributed to the self, whereas negative events are ascribed to the external environment. In contrast, the cognitive deficit model (CDM) focuses on cognitive impairments and distortions of threat evaluating mechanisms as the cause for delusion formation. ^[18]

The mental status examination (including cognitive examination) in delusional disorder is usually normal other than the presence of abnormal delusional beliefs.

In general, patients are well groomed and well-dressed without evidence of gross impairment. Speech, psychomotor activity, and eye contact may reflect the emotional state associated with delusions, but are otherwise normal.

Mood and affect are consistent with delusional content; for example, patients with persecutory delusions may be suspicious and anxious. Mild dysphoria may be present without regard of type of delusions.

Tactile and olfactory hallucinations may be present if they are related to the delusional theme (eg, the sensation of being infested by insects, the perception of body odor). ^[19] Systemic or focal CNS causes of tactile and olfactory hallucinations, such as substance intoxication and/or withdrawal, temporal lobe epilepsy, should be ruled out. Auditory or visual hallucinations stereotypically characteristic of more severe psychotic disorders (eg, schizophrenia) are not consistent with a diagnosis of delusional disorder.

Memory and cognition are intact. Level of consciousness is unimpaired.

Patients usually have little insight and impaired judgment regarding their delusions. Police, family members, coworkers, and physicians other than psychiatrists are usually the first to suspect delusional disorder and often encourage the patient to seek psychiatric consultation. Seeking corroborative collateral information is often crucial. Recall that it is permissible to seek collateral history, and that collateral history should not be withheld from the patient.

Assessment of homicidal or suicidal ideation is extremely important in evaluating patients with delusional disorder. The presence of homicidal or suicidal thoughts related to delusions should be actively assessed and the risk of carrying out violent plans should be ascertained. A review by researchers revealed a 8–21% risk of suicidal ideation and behavior in the persecutory and somatic subtypes. ^[20] Reid pointed out that some types of delusional disorder—erotomanic, jealous, and persecutory—are associated with higher risk for violence than others. ^[21] History of previous violent acts as well as history of how aggressive feelings were managed in the past may help to assess the risk. Access to weapons needs to be explored.

Erotomanic type

Related terms include erotomania, psychose passionelle, de Clerambault syndrome, and old maid's insanity. ^{[11, 4, 10]}

The central theme of delusions is that another person, usually of higher social status, is in love with the patient. The object of delusion is usually married, geographically and/or socially distant, or otherwise unavailable. ^{[22, 10]}

Patients with this type of delusion are usually female, although males predominate in forensic samples. ^{[1, 10]}

Erotomania is usually intense. Signs of denial of love by the delusionally desired love object are frequently paradoxically and falsely interpreted as affirmation of love. ^{[11, 10]}

Patients may attempt to contact the object of the erotomanic delusion by initiating email and other electronic communications, making telephone calls, sending letters and gifts, making unwanted visits, and even stalking. Some cases lead to assaultive behaviors as a result of attempts to pursue the object of delusional love or attempting to "rescue" her/him from some imagined danger. ^[1]

Grandiose type

Patients believe that they possess some great and unrecognized talent, have made some important discovery, have a special relationship with a prominent person, and/or have special religious insight. ^[1]

Grandiose delusions in the absence of a manic episode are relatively uncommon. Many patients with paranoid type show some degree of grandiosity in their delusions. ^[4]

Grandiosity in narcissistic personality disorder is by definition nonpsychotic and not directly and solely related to hypomanic or manic episodes, as in bipolar disorder. Narcissistic personality disorder patients will concurrently show a lack of empathy, exploitative social behavior, jealousy, and/or a sense of entitlement, in addition to grandiosity.

Jealous type

Related terms include conjugal paranoia, Othello syndrome, and pathological or morbid jealousy. ^{[3, 6, 23, 24]}

The main theme of the delusions is that the patient's spouse or lover is unfaithful. Some degree of infidelity may in fact occur; however, patients with delusional jealousy support their accusation with delusional interpretation of "evidence" that may be innocuous (e.g., disarrayed clothing, spots on the bedsheets). ^{[1, 4]}

Patients may attempt to confront their spouses and intervene in imagined infidelity situations. Jealousy may evoke anger and empower the jealous individual with a sense of righteousness to justify acts of aggression towards the spouse/partner and/or the imagined paramour. Both the intimate partner and the (perceived) lover may be the targets of aggression and violence. This disorder can lead to acts of violence, including suicide and homicide. ^[4]

Persecutory type

This is the most common type of delusional disorder. ^{[5, 25]}

Patients with this type believe that they are being persecuted and/or harmed. ^[4] In contrast to persecutory delusions of schizophrenia, which may be fundamentally bizarre, the delusions are systematized, coherent, and defended with clear logic. Otherwise, no deterioration in social functioning and/or personality is observed. ^[11]

Patients may pursue formal litigation against their perceived persecutors. Munro ^[22] refers to an article by Freckelton who identified the following characteristics of delusional litigants: determination to succeed against all odds, tendency to identify barriers to justice as conspiracies, endless drive to "right a wrong," quarrelsome behaviors, and "saturating the field" with multiple complaints and suspiciousness. ^[22]

Patients often experience some degree of emotional distress such as irritability, anger, and resentment. ^[4] In extreme situations, they may resort to violence against those who they believe are threatening and/or hurting them. ^[1]

The distinction between normality, overvalued ideas, and delusions can be difficult to make in some cases. ^[4]

Somatic type

The core beliefs of this type are delusions around bodily functions and sensations. The most common are beliefs that one is infested with insects or parasites, that one is emitting a foul odor, that parts of the body are not functioning, that the body or parts of the body are misshapen or ugly, or the reduplication of body parts. ^{[1, 13]}

Patients are strongly convinced in the "physical" nature of this disorder, as opposed to patients with a hypochondriacal presentation who may be able to admit that their fear of having a serious illness is groundless. ^[11]

Patients are usually first seen by dermatologists, plastic surgeons, urologists, gastroenterologists, and other medical specialists. ^[4]

Sensory experiences associated with somatic delusions (e.g., sensation of parasites crawling under the skin) are viewed as components of systemized delusions. ^[4] This must be distinguished from bizarre somatic delusions occasionally seen in schizophrenia (e.g., a delusion that a "colony of lobsters" is living in the patient’s stomach).

Mixed type

Patients exhibit more than one of the delusions simultaneously ^[4] , and no one delusional theme predominates. ^[1]

Unspecified type

Delusional themes fall outside the above specific categories and/or cannot be clearly determined. ^[1]

Misidentification syndromes such as Capgras syndrome (characterized by a belief that a familiar person has been replaced by an identical "impostor") or Fregoli syndrome (a belief that a familiar person is "disguised" as someone else) fall into this category. These misidentification syndromes are rare and frequently, when present, associated with other neuropsychiatric conditions (e.g., schizophrenia, neurocognitive disorders, epilepsy, post-CVA). ^[4]

Another unusual syndrome is Cotard syndrome, in which patients believe that they have lost all their possessions, status, and strength as well as their entire being, including their organs. ^[4] Described first in the 19th century, it is a rare condition, which is usually considered a precursor to a psychotic or depressive episode. ^[11]

Table 1. Various Medical Conditions Associated With Development of Delusions ^[4] (Open Table in a new window)

Table 2. Related/Overlapping Psychiatric Disorders and Differentiating Features (Open Table in a new window)

General considerations

Delusional disorder is challenging to treat for various reasons, including the patient's frequent denial that they have any problem, especially with a psychological explanation, difficulties in developing a therapeutic alliance, and social/interpersonal conflicts.

Treatment principles include the following:

• Establish a therapeutic alliance and negotiate mutually acceptable symptomatic treatment goals. Start where "the patient is at," and offer empathy, concern, and interest in the patient's experiences.

• With the appropriate permission from the patient, include the patient's family members in decision-making and educate them.

• Consider the impact of culture on illness experience.

• Avoid direct confrontation of the delusional symptoms to enhance the possibility of treatment compliance and response.

• Use medication judiciously to target core symptoms and associated problems (eg, depressed mood, irritability).

• Use outpatient treatment unless there is high likelihood of self-harm or violence and/or an inability to care for self. Inpatient hospitalization is needed if a patient's delusions cause him or her to be a threat to self or others, or if he or she is deemed to be gravely disabled.

• Tailor treatment strategies to the individual needs of the patient and focus on maintaining social function and improving quality of life.

• Recognize and treat comorbid psychiatric disorders.

Psychopharmacological treatment

The evidence for the psychopharmacological treatment of delusional disorder is considered grade C (case series) or grade D (single case studies) evidence in many evidence-based medicine hierarchies. This is in contrast to randomized, blinded studies (grade A) or nonrandomized or nonblinded, but still systematically conducted, studies (grade B).

Antipsychotics have been used since the 1970s when the first report was published on the use of pimozide for the treatment of monosymptomatic hypochondriacal psychosis (now classified as a delusional disorder, somatic type by DSM-5-TR). Of approximately 1000 treated cases of delusional disorder from 1965-1985, a subanalysis of 257 best-described cases revealed that delusional disorder has a relatively good prognosis when adequately treated — 52.6% of the patients recovered, 28.2% achieved partial recovery, and 19.2% did not improve. Treatment response was positive regardless of the specific delusional content. The data concluded that pimozide (68.5% recovery rate and 22.4% partial recovery rate) may be better than other typical antipsychotics (22.6% recovery and 45.3% partial recovery). ^[28]

Data since that time still consists mostly of case reports. The most recent review of treatment for delusional disorder included 224 case reports published since 1995, though only 134 case reports were well described. ^[7] The following is the summary of their findings:

• In general, delusional disorders were reported to be moderately responsive to treatment (50% of the published patients reported symptom-free recovery and 90% of patients showed at least some improvement).

• Combination treatment was common. Polypharmacy was common, most often including a combination of antipsychotic and antidepressant medication. In addition, patients commonly received more than one antipsychotic over the course of their illness, and medication treatments were also complemented by other interventions, such as cognitive-behavioral therapy or even (in a single case) electroconvulsive therapy (ECT).

• In contrast to previous findings, no significant difference was observed between treatment with pimozide and other antipsychotics. Indeed, no difference was observed between typical and atypical antipsychotic agents.

• Somatic delusions appeared potentially more responsive to antipsychotic therapy than other types of delusions (regardless of whether this treatment was pimozide or other antipsychotics). However, this apparent difference may mostly result from the generally poor response rates for delusional disorder with persecutory delusions (50% improvement rates, with no reports of complete recovery).

• No other predictors of a positive outcome have been studied or clearly elucidated (eg, age, gender, symptom severity, positive family history, or premorbid function).

Systematic reviews of the literature shows that olanzapine and risperidone are the most common second-generation antipsychotics used; however, some evidence shows a superior response to first-generation agents. ^{[29, 30, 31, 32]} Four reports (5 cases) of individuals with delusions presumably refractory to previous antipsychotic treatment reported that clozapine was associated with an improved quality of life and a decrease in symptoms associated with the delusion, although the central delusional theme often persisted. In contrast, as indicated above, some cases of delusional disorder appear refractory even to clozapine treatment. ^[7]

Reviews of treatment of delusional disorder have not systematically addressed the question of what dose of antipsychotics is recommended forremission. However, a study of 11 patients with delusional disorder appeared to be adequately treated on fairly low doses of antipsychotic (4.7 mg of haloperidol per day). ^[15]

Antidepressants have been successfully used for the treatment of delusional disorder, although primarily of the somatic type. The data consist of case reports showing improvement with selective serotonin reuptake inhibitor (SSRI) ^[33] and clomipramine treatments ^{[34, 35]} . Several case reports documented successful treatment with SSRI for culture-bound syndromes (conditions that would be diagnosed as somatic type of delusional disorder in Western cultures). ^[36]

There is a single case report of successful ECT use for somatic delusions. ^[37]

In summary, a reasonable pharmacological treatment approach for the patient with delusional disorder is a standard trial of an antipsychotic or, for somatic delusions, an SSRI.

Psychotherapy

For many patients with delusional disorder, some form of supportive psychotherapy may be helpful. The goals of supportive therapy include facilitating treatment adherence and providing education about the illness and its treatment. Educational and social interventions can include social skills training (eg, not discussing delusional beliefs in social settings) and minimizing risk factors that may increase symptoms, including sensory impairment, isolation, stress, and precipitants of violence. Providing realistic guidance and assistance in dealing with problems stemming from the delusional system may be very helpful. ^[38]

Cognitive psychotherapeutic approaches may be useful for some patients; this is best studied in persecutory type. The therapist helps the patient to identify maladaptive thoughts by means of Socratic questioning and behavioral experiments and then replaces them with alternative, more adaptive beliefs and attributions. Discussion of the unrealistic nature of delusional beliefs should be done gently and only after rapport with the patient has been established. ^{[39, 38, 40]} Specific areas of cognitive experience and processing in delusional disorders that may be amenable to cognitive-based psychotherapy techniques include addressing the interpretation of anomalous internal experiences, styles of reasoning regarding experiences, negative thoughts about the self, and interpersonal sensitivity. ^{[41, 42]}

One study evaluated the effectiveness of cognitive-behavioral therapy (CBT) versus attention placebo control (APC) as a means to treat delusions in delusional disorder. Using the Maudsley Assessment of Delusions Schedule (MADS), the study found that both APC and CBT improved belief and mood parameters associated with delusions. However, CBT produced more of an impact when compared to APC on strength of conviction, affect relating to belief, and positive actions of beliefs, suggesting CBT as a successful means of treating delusional disorder. ^[43]

According to Liberman ^[44] , another technique that may be applicable to a wider population of persons with delusional disorder is behavioral principles and social skills training to provide the individual with effective means of "feeling in control" and less subject to viewing others' efforts to harm him/her as allowing "them" to be controlling. Social skills training focuses on promoting interpersonal competence, confidence (with successful use of more competent social skills) and comfort in interacting with those who the individual feels are judging and having harmful intent toward him/her. Taking control and initiative can dissipate the feeling of loss of control that feeds into and reinforces the delusions.

The literature also states that insight-oriented psychotherapy may be indicated, only rarely ^[38] or even contraindicated for delusional disorder ^[11] . However, reports exist of successful treatment with these approaches. ^[39] Goals in insight-oriented psychotherapy include development of the therapeutic alliance; containment of projected feelings of hatred, badness, and impotence; measured interpretation; and, ultimately, development of a sense of creative doubt in the internal perception of the world through empathy with the patient's defensive position. ^[39]