Delusional Disorder

Etiology

Delusional disorder is relatively rare, has a later age of onset as compared to schizophrenia, and does not show a gender predominance. The patients are also relatively stable. The exact cause of the delusional disorder is unknown.[2]

Many biological conditions like substance use, medical conditions, neurological conditions can cause delusions. The delusional disorder involves the limbic system and basal ganglia in those with intact cortical functioning.[3]

Hypersensitive persons and ego defense mechanisms like reaction formation, projection, and denial are some psychodynamic theories for delusional disorder. Social isolation, envy, distrust, suspicion, and low self-esteem are some of the factors which when becoming intolerable leads to a person seeking an explanation and thus forming a delusion as a solution.[2]

Immigrants with language barriers, deaf and visually impaired persons, as well as the elderly, are special populations who are more vulnerable to delusions.

Epidemiology

The lifetime morbid risk of delusional disorder in the general population has been estimated to range from 0.05 to 0.1%, based on data from various sources including case registries, case series, and population-based samples. According to the DSM-V, the lifetime prevalence of delusional disorder is about 0.02%.[3] The prevalence of the delusional disorder is much rarer than other conditions like schizophrenia, bipolar disorder, and other mood disorders; this may be in part due to underreporting of delusional disorder as those with delusional disorder may not seek mental health attention unless forced by family or friends. Age mean age of onset is about 40 years, but the range is from 18 years to 90 years. The persecutory and jealous type of delusion is more common in males, while the erotomanic variety is more common in females.

Pathophysiology

Generally, global functioning is more or less preserved as compared to other disorders. Impairment can be significant in one's occupation. There may be social isolation. A unique finding is apparent normal psychological functioning and appearance when not discussing the specific delusion. 

• Persecutory type: This is one of the most common types of delusions and patients can be anxious, irritable, aggressive, or even assaultive - some patients may be litigious.
• Jealous type: Also known as “ Othello syndrome” this type is more common in males; it can sometimes correlate with suicidal or homicidal ideations, and hence safety is an important consideration in evaluation and management.[4]
• Erotomanic type: Also known as “ psychose passionelle” this type of delusion involves a belief that a person usually of higher stature is in love with the patient.[5] These patients are usually socially withdrawn, dependent, sexually inhibited with a poor level of social and/or occupational functioning. “Paradoxical conduct” is an important characteristic wherein all denials of affection are rationalized as affirmations.[6] Males with this type of delusion can be more aggressive.[7]
• Somatic type: Also called monosymptomatic hypochondriacal psychosis and the reality impairment is severe. The patient is unarguably convinced of the severity of the symptoms. The most common type of somatic delusions is that of infestation example with parasites, body dysmorphic delusion, and of body odor or halitosis. These patients also have anxiety and nervousness.
• Grandiose type: Also known as megalomania are notable for increased self-importance.
• Mixed type: Patients have two or more delusional themes.
• Unspecified type: Sometimes a predominant delusion cannot be identified. Capgras syndrome is a delusional syndrome where there is a belief that a known person has been replaced by an impostor.[1] Cotard syndrome is when a patient believes he has lost his possessions, status, and even bodily organs.[1]

Delusional disorder in the partner of an individual with the delusional disorder: This is also known as a shared psychotic disorder.

History and Physical

General description: Patients are usually well-nourished, appropriately groomed. It may seem odd, suspicious, can be litigious. Patients seek an ally in the clinician, but it is important not to accept the delusion as it eventually results in confusing the patient’s reality and leads to distrust.[3]

Mood: Mood is usually congruent with the delusion, for example, a grandiose patient may be euphoric, or a paranoid patient may be anxious. Mild depressive symptoms are present.[8]

Perceptions: Usually no abnormal perceptions are present. Auditory hallucinations may be present in some.

Thought: This is the primary abnormality in delusional disorder. The delusions are not bizarre and are clear as well as systematic for example a cheating spouse, persecutory delusions. It is essential to check the patient's belief before concluding it to be a delusion. Some patients are verbose and circumstantial when describing their delusions. Bizarre delusions more likely correlate with schizophrenia.[3]

Cognition: Memory and cognition are usually intact, and patients are oriented unless there is a specific delusion about person, place, or time.

Impulse control: It is important to evaluate for suicidal or homicidal ideations and plans. If there is a history of aggression with adverse action, then hospitalization should be considered.

Insight and judgment: Most commonly patients have no insight regarding their delusion. Judgment is assessable by a history of past behavior and future plan.

Evaluation

Although there is no set of labs required for a delusional disorder like most other psychiatric disorders. Imaging or laboratory tests should be considered to rule out any organic causes. Substance-induced conditions should be ruled out by getting a urine drug screen. After an organic cause is ruled out a clinical exam should be completed. A clinician would do an assessment and ask further questions about their delusions. During the assessment, a complete mental status exam should be done. Interviewing family members and friends should be considered because they can provide further details about the delusions and more importantly a timeline of the presenting symptoms.

Treatment / Management

The treatment of delusional disorder is difficult considering the lack of insight. A good doctor-patient relationship is a key to treatment success. Treatment includes psychotherapy by establishing trust and building a therapeutic alliance. 

A patient's history of medication compliance is the best guide to select appropriate antipsychotic medication. An antipsychotic should be started for a trial period of six weeks after which there is an evaluation of the effectiveness of the medication. Start a low dose and titrate up as needed. Another drug from another class can be tried after six weeks if no benefit is noted from initial treatment.[9]

Though not a primary indication drugs like lithium, valproic acid, and carbamazepine can be considered as an adjunct treatment if monotherapy with antipsychotics fails.

Treatment response is better when combining psychotherapy with psychopharmacology.

Differential Diagnosis

1. Obsessive-compulsive disorder: A person who remains convinced that his/her obsessions and compulsions are true convictions, should be given the diagnosis of obsessive-compulsive disorder with absent insight.
2. Schizophreniform and schizophrenia: This can be differentiated from delusional disorder by the presence of other symptoms of the active phase of schizophrenia.[10]
3. Delirium/major neurocognitive disorder: Can mimic delusional disorder but distinguished based on the chronology of symptoms.
4. Depression or bipolar disorder: Delusions occur with mood episodes. A delusional disorder is diagnosed only when the span of delusions exceeds the total duration of mood symptoms.

Prognosis

The prognosis of delusional disorder is better with treatment and medication compliance. Almost 50% of patients have a good response to medications; more than 20% of patients report a decrease in symptoms and less than 20% of patients report minimal to no change in symptoms. Delusional disorder is usually a chronic condition, but when properly treated. A good prognosis is also related to higher social and occupational functioning, early-onset before age 30 years, female, sudden onset of symptoms, and short duration.[2]

Complications

The delusional disorder, if left untreated, might lead to depression, often as a consequence of difficulties associated with the delusions. Delusions also can lead to violence or legal issues; for instance, stalking or harassing the object of delusion, could lead to arrest. Further, patients suffering from this disorder can become alienated from others, particularly if their delusions interfere with their social ties.