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Delusions are fixed beliefs that do not change, even when a person is presented with conflicting evidence. Delusions are considered "bizarre" if they are clearly implausible and peers within the same culture cannot understand them. An example of a bizarre delusion is when an individual believes that his or her organs have been replaced with someone else's without leaving any wounds or scars. An example of a non-bizarre delusion is the belief that one is under police surveillance, despite a lack of evidence.

Delusional disorder refers to a condition in which an individual displays one or more delusions for one month or longer. Delusional disorder is distinct from schizophrenia and cannot be diagnosed if a person meets the criteria for schizophrenia. If a person has delusional disorder, functioning is generally not impaired and behavior is not obviously odd, with the exception of the delusion. Delusions may seem believable at face value, and patients may appear normal as long as an outsider does not touch upon their delusional themes. Also, these delusions are not due to a medical condition or substance abuse.

There are several different types of delusional disorders, and each type captures a particular theme within a person's delusions.

  • Erotomanic: An individual believes that a person, usually of higher social standing, is in love with him or her.
  • Grandiose: An individual believes that he or she has some great but unrecognized talent or insight, a special identity, knowledge, power, self-worth, or relationship with someone famous or with God.
  • Jealous: An individual believes that his or her partner has been unfaithful.
  • Persecutory: An individual believes that he or she is being cheated, spied on, drugged, followed, slandered, or somehow mistreated.
  • Somatic: An individual believes that he or she is experiencing physical sensations or bodily dysfunctions, such as foul odors or insects crawling on or under the skin, or is suffering from a general medical condition or defect.
  • Mixed: An individual exhibits delusions that are characterized by more than one of the above types, but no one theme dominates.
  • Unspecified: An individual's delusions do not fall into the described categories or cannot be clearly determined.

The primary feature of delusional disorder is the presence of one or more delusions that persist for at least one month. These delusions can be considered bizarre if they are clearly not possible and peers within the same culture cannot understand them. Alternatively, non-bizarre delusions reflect situations that occur in real life but are not actually happening in the life of the person with the delusion.

People with delusional disorder typically function well aside from their delusion(s) and do not exhibit obviously odd or bizarre behavior.​ If the individual is to be diagnosed with delusional disorder, any manic or major depressive episode he or she has suffered must be brief in duration relative to the delusional periods. Additionally, the delusions must not be attributable to the effects of a substance or other medical condition.

Anger and violent behavior may be present if someone is experiencing persecutory, jealous, or erotomanic delusions. In general, people with delusional disorder are not able to accept that their delusions are irrational or inaccurate, even if they are able to recognize that other people would describe their delusions this way.

What is the most frequent type of delusional disorder?

The most frequent type is the persecutory delusion. This paranoid thinking can be severe—law enforcement is bugging the phone, for example. People with this type of delusion may suffer from illnesses such as schizophrenia, bipolar disorder, or dementia.

Can a person know that they are experiencing a delusion?

A person can be aware that they are gripped by a belief that others do not endorse and may even actively attempt to disprove, but the belief feels so overwhelmingly true that they cannot shake it, despite evidence to the contrary. A person who has experienced past delusions and no longer does (for example, due to the use of antipsychotic medication), may realize that their former belief was false, and thereby have insight into the fact that they are prone to delusions. This knowledge may help them manage future breaks with reality.

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Delusional disorder is a rare condition and difficult to study; as a result, it is not widely discussed in clinical research. While the cause is unknown, some studies suggest that people develop delusions as a way to manage extreme stress or deal with a history of trauma. Genetics may also contribute to the development of a delusional disorder. Individuals are more likely to be diagnosed with delusional disorder if they have family members with schizophrenia or schizotypal personality disorder. An imbalance of chemicals or abnormalities in the brain can play a part in delusions.

What is the prevalence of delusional disorder?

This condition is rare, with an estimated 0.2 percent of people experiencing it at some point in their lifetime. Delusional disorder is equally likely to occur in males and females. Onset can vary from adolescence to late adulthood but tends to appear later in life.

What is shared delusional disorder?

Shared delusional disorder involves a more controlling person, often older, and a more passive person, often younger. When the controlling individual is removed from the situation, the more passive participant is often relieved of the delusions. 


Delusional disorder is a challenging condition to treat. People with this condition will rarely admit that their beliefs are delusions or are problematic, and will therefore rarely seek out treatment. If they are in treatment, their provider may find it difficult to develop a therapeutic relationship with them.

Careful assessment and diagnosis are critical to the treatment of delusional disorders. Because delusions are often ambiguous and are present in other conditions, it may be difficult to zero in on a diagnosis of delusional disorder. Additionally, coexisting psychiatric disorders should be identified and treated accordingly.

Treatment of delusional disorder often involves both psychopharmacology and psychotherapy. Given the chronic nature of this condition, treatment strategies should be tailored to the individual needs of the patient and focus on maintaining social function and improving quality of life. Establishing a therapeutic alliance as well as establishing treatment goals that are acceptable to the patient should be prioritized. Avoiding direct confrontation of the delusional symptoms enhances the possibility of treatment compliance and response. Hospitalization should be considered if the potential for self-harm or violence exists.

Antipsychotic medications may be used in the treatment of delusional disorder, although research on the efficacy of this form of treatment has been inconclusive. Studies have shown that somatic delusions appear potentially more responsive to antipsychotic therapy than other types of delusions. Antidepressants, such as SSRIs and clomipramine, have also been successfully used for the treatment of somatic type delusional disorder.

For most patients with delusional disorder, some form of supportive therapy is 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 (such as not discussing delusional beliefs in social settings) and minimizing risk factors, including sensory impairment, isolation, stress, and precipitants of violence. Providing realistic guidance and assistance in dealing with problems stemming from the delusional disorder may be helpful.

Cognitive therapeutic approaches may be useful for some patients. In this form of therapy, the therapist uses interactive questioning and behavioral experiments to help the patient to identify problematic beliefs and then replace them with alternative, more adaptive thinking. Discussion of the unrealistic nature of delusional beliefs should be done gently and only after rapport with the patient has been established.

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How can a person with delusional disorder be encouraged to seek help?

Family, friends, and peer groups can provide support and encouragement. A patient who feels pressured or repeatedly criticized by others will likely experience stress, which can lead to a worsening of symptoms. A positive approach may be more helpful and perhaps more effective in the long run. In addition, setting goals that are attainable will help.

Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition
National Institutes of Health
Fochtmann, L. J., Treatment of other psychotic disorders. Kaplan & Sadock's Comprehensive Textbook of Psychiatry. 8th ed.
Manschreck T. C., Delusional and Shared Psychotic Disorder. Kaplan & Sadock's Comprehensive Textbook of Psychiatry 7th ed.
Fear, C. F., (2013). Recent developments in the management of delusional disorders. Advances in Psychiatric Treatment, 19(3), 212–220.  
Turkington D., Kington D., Weiden P., Cognitive-behaviour therapy for schizophrenia: A review. Current Opinions Psychiatry. 2005; 18(2):159–163.
Last updated: 04/06/2022