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Delusional Disorder - Harvard Health Skip to main content Recent Articles Why testosterone levels drop and when to consider treatment Don't count on daily aspirin to prevent colon cancer Night owls' habits linked to worse heart health After ablation, exercise may lower atrial fibrillation recurrence What can cause an enlarged heart? Women's unique risks for heart disease Chronic kidney disease: A hidden threat to your heart Navigating your online patient portal: Best practices Treating hair loss in men: What works? Virtual cardiac rehab: Heal your heart from home / January 27, 2025 Reviewed by Howard E. LeWine, MD , Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing Share Share this page to Facebook Share this page to X Share this page via Email Copy this page to clipboard Print This Page Click to Print What is it? Delusional disorder is characterized as having one or more false beliefs based on an incorrect interpretation of reality lasting at least one month. Other than the delusions, the person usually appears to function normally. Delusions can occur as part of many different psychiatric disorders. But the term delusional disorder is used when delusions are the most prominent symptom. A person with this illness holds a false belief firmly, despite clear evidence or proof to the contrary. Delusions may involve circumstances that could occur in reality even though they are unlikely (for example, the family next door plotting to kill you). Or they may be considered bizarre (for example, feeling controlled by an outside force or having thoughts inserted into your head). A religious or cultural belief that is accepted by other members of the person's community is not a delusion. There are several types of delusions: persecutory, erotomatic, grandiose, jealous, or somatic (that is, delusions about the body). People with delusional disorder usually do not have hallucinations or a major problem with mood. Unlike people with schizophrenia, they tend not to have major problems with day-to-day functioning. Other than behaviors related to delusional content, they do not appear odd. When hallucinations do occur, they are part of the delusional belief. For example, someone who has the delusion that internal organs are rotting may hallucinate smells or sensations related to that delusion. If functioning is impaired, it is usually a direct result of the delusion. Therefore, the disorder may be detected only by observing behavior that is a consequence of the belief. For example, a person who fears being murdered may quit a job or stay home with all the shades drawn, never venturing out. Since people with delusional disorder are aware that their beliefs are unique, they generally do not talk about them. Delusional disorder is diagnosed much less frequently than schizophrenia. Symptoms The main symptom is a persistent delusion or delusions (a fixed belief) - for example, about a situation, condition, or action - that is not happening but may be plausible in real life. Types include: Erotomanic - Delusion of a special, loving relationship with another person, usually someone famous or of higher standing. (This kind of delusion is sometimes at the root of stalking behavior.) Grandiose - Delusion that the person has a special power or ability, or a special relationship with a powerful person or figure such as the president, a celebrity, or the Pope. Jealous - Delusion that a sexual partner is being unfaithful. Persecutory - Delusion that the person is being threatened or maltreated. Somatic - Delusion of having a physical illness or defect. Diagnosis Since delusional disorder is rare, a doctor should evaluate the possibility that another major illness, such as schizophrenia, a mood disorder, or a medical problem, is causing the symptoms. Medical causes should be considered, especially later in life. People who develop dementia (for example, Alzheimer's disease) can become delusional. Making a diagnosis is more difficult when the person with the disorder conceals his or her thoughts. Because the person is convinced of the reality of his or her ideas, he or she may not want treatment. If the person allows it, conversations with supportive family or friends can help. A general medical evaluation is useful. In a few cases, when a medical or neurological problem is suspected, diagnostic tests such as an electroencephalogram (EEG), magnetic resonance imaging (MRI), or computed tomography (CT) scans may be suggested. Expected duration How long this illness lasts varies a lot. Some people have a persistent delusion that comes and goes in its intensity and significance. In some, the disorder will last only a few months. Prevention There is no known way to prevent this disorder. Treatment Treatment for this disorder is challenging, especially if the delusion is long-lasting. Antipsychotic medications can be helpful, but delusions sometimes do not get better with pharmacological treatment. Since patients may not believe they have a mental disorder, they may refuse all treatment, including psychotherapy. However, support, reassurance, and pointing out the difference between the symptoms and reality can all be helpful if the person is willing to meet with a therapist. Educating the family about how to respond to the person's needs can be useful. When to call a professional Call the person's primary care doctor, a psychiatrist, or other mental health professional as soon as the problem is detected. Prognosis The outlook varies. Although the disorder can go away after a short time, delusions also can persist for months or years. The inherent reluctance of a person with this disorder to accept treatment makes the prognosis worse. However, people with this disorder retain many areas of functioning, so some do reasonably well with limited assistance. Additional info American Psychiatric Association https://www.psychiatry.org/ American Psychological Association https://www.apa.org/ National Institute of Mental Health https://www.nimh.nih.gov/ About the Reviewer Howard E. LeWine, MD , Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD Share Share this page to Facebook Share this page to X Share this page via Email Copy this page to clipboard Print This Page Click to Print Disclaimer: As a service to our readers, Harvard Health Publishing provides access to our library of archived content. Please note the date of last review or update on all articles. No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician. Recent Articles Why testosterone levels drop and when to consider treatment Don't count on daily aspirin to prevent colon cancer Night owls' habits linked to worse heart health After ablation, exercise may lower atrial fibrillation recurrence What can cause an enlarged heart? Women's unique risks for heart disease Chronic kidney disease: A hidden threat to your heart Navigating your online patient portal: Best practices Treating hair loss in men: What works? 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