Merck Manual

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Delusional Disorder

By

Carol Tamminga

, MD, UT Southwestern Medical Dallas

Last full review/revision May 2020| Content last modified May 2020
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NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version

Delusional disorder is characterized by one or more firmly held false beliefs that persist for at least 1 month.

  • The false beliefs may be ordinary things that could occur (such as being deceived by a spouse) or things unlikely to occur (such as having internal organs removed without leaving a scar).

  • This disorder may develop in people with a paranoid personality disorder.

  • Doctors base the diagnosis mainly on the person’s history after they rule out other possible causes.

  • People usually remain functional and employed.

  • A good doctor-patient relationship is essential to treatment.

Delusional disorder usually first affects people in middle or late adult life. It is less common than schizophrenia. Delusional disorder is distinguished from schizophrenia by the presence of delusions without any of the other symptoms of psychosis (for example, hallucinations, disorganized speech, or disorganized behavior).

Delusions may involve situations that could conceivably occur in real life, such as being followed, poisoned, infected, or loved at a distance. Or they may involve situations that are very unlikely to occur, such as having internal organs removed without leaving a scar. The difference between a delusion and a false or mistaken belief is that people continue to believe in a delusion no matter how much clear evidence contradicts it.

Types of delusional disorder

There are several subtypes of delusional disorder:

  • Erotomanic: People believe that another person is in love with them. They often try to contact the object of the delusion through telephone calls, letters, or digital messages. Some attempt surveillance, and stalking is common. Behavior related to the delusion may be against the law.

  • Grandiose: People are convinced that they have some great talent or have made some important discovery.

  • Jealous: People are convinced that a spouse or lover is unfaithful. This belief is based on incorrect inferences supported by dubious evidence. Under such circumstances, physical assault may be a significant danger.

  • Persecutory: People believe that they are being plotted against, spied on, maligned, or harassed. People may repeatedly file lawsuits or reports to the police or other government agencies. Rarely, people resort to violence in retaliation for imagined persecution.

  • Somatic: People are preoccupied with a bodily function or attribute, such as an imagined physical deformity or odor. The delusion can also take the form of an imagined medical disorder, such as having parasites.

Symptoms

A delusional disorder may develop from a preexisting paranoid personality disorder. Beginning in early adulthood, people with a paranoid personality disorder have a pervasive distrust and suspiciousness of others and their motives.

Early symptoms of delusional disorder may include

  • Feeling exploited

  • Being preoccupied with the loyalty or trustworthiness of friends

  • Reading threatening meanings into benign remarks or events

  • Bearing grudges for a long time

  • Responding readily to perceived slights

Behavior is not obviously bizarre or odd. People with delusional disorder tend to function relatively well, except when their delusions cause problems. For example, they may have marital problems if they are incorrectly convinced their spouse is being unfaithful.

Diagnosis

  • A doctor's evaluation

After ruling out other specific conditions that can cause delusions (such as a substance use disorder), a doctor bases the diagnosis largely on the person’s history and symptoms. The doctor also must assess how dangerous the person might be, particularly how likely the person is to act on the delusions.

Prognosis

Delusional disorder does not usually cause severe impairment. However, people may become progressively more involved with their delusion.

Most people are able to remain employed, as long as their work does not involve people or events related to their delusions.

Treatment

  • Establishment of a good doctor-patient relationship

  • Sometimes antipsychotic drugs

Treatment can be difficult because some people firmly believe their delusion and refuse to seek help. A good doctor-patient relationship helps. Once a relationship is established, doctors can encourage people who are resistant to being treated to participate in treatment.

Hospitalization may be needed if the doctor believes that people are dangerous.

Antipsychotic drugs are not generally used but are sometimes effective in reducing symptoms.

A long-term treatment goal is to shift the person’s focus away from the delusion to a more constructive and gratifying area, although this goal is frequently difficult to achieve.

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
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