Patient Basics: Delusional Disorder

Originally published by Harvard Health.

What Is It?

Delusional disorder is classified as a psychotic disorder, a disorder where a person has trouble recognizing reality. A delusion is a false belief that is based on an incorrect interpretation of reality. Delusions, like all psychotic symptoms, 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, erotic, 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 and 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 their 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.


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.


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 affected person 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.


There is no known way to prevent this disorder.


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.


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
1000 Wilson Blvd.
Suite 1825
Arlington, VA 22209-3901
Phone: 703-907-7300
Toll-Free: 1-888-357-7924

American Psychological Association
750 First St., NE
Washington, DC 20002-4242
Phone: 202-336-5510
Toll-Free: 1-800-374-2721
TTY: (202) 336-6123

National Institute of Mental Health
Office of Communications
6001 Executive Blvd.
Room 8184, MSC 9663
Bethesda, MD 20892-9663
Phone: 301-443-4513
Toll-Free: 1-866-615-6464
TTY: 301-443-8431
Fax: 301-443-4279

National Alliance for the Mentally Ill
Colonial Place Three
2107 Wilson Blvd.
Suite 300
Arlington, VA 22201-3042
Phone: 703-524-7600
Toll-Free: 1-800-950-6264
TTY: 703-516-7227
Fax: 703-524-9094