Delusional Disorder is a psychiatric illness that afflicts a very small percentage of the population. This diagnosis accounts for approximately 1-2% of admissions to inpatient psychiatric facilities. The best estimate for the prevalence of this disorder in the general population is approximately 0.03%. This article describes delusions and Delusional Disorder and the types of delusional themes that can occur.


Delusions are beliefs that are clearly false and not based in reality. Delusional beliefs are not accounted for by a person’s intelligence or background and one of the key features of a delusion is the extent to which the person holds firm to this belief, even in the face of disconfirming evidence or proof to the contrary. Delusions can be difficult to distinguish from overvalued ideas, which are unreasonable beliefs to which a person holds but with some level of doubt. Recent research indicates that abrupt onset, implausible content, and relative indifference to the opinions of others may be better distinguishing features for delusions as compared to overvalued ideas. Individuals with delusional beliefs are absolutely convinced that their beliefs are true.

Three criteria for Delusions

In the early 1900s the psychiatrist Karl Jaspers set out three main criteria for a delusional belief:

  1. certainty (the belief is held with absolute conviction);
  2. incorrigibility (the belief is immune to change by compelling counterargument or proof to the contrary); and
  3. impossibility (implausible, patently untrue, or bizarre; simply not based in reality)

Categorization of Delusions

Delusions are categorized as bizarre or nonbizarre and as mood-congruent or mood-neutral.

  • Bizarre delusions are beliefs that are strange and completely implausible, such as having a piece of one’s anatomy removed (when it clearly has not been)
  • Non-Bizarre delusions are beliefs that, although false, are at least possible, such as the person believing that she is being followed or watched
  • Mood-Congruent delusions contain content that are consistent with mood states (depression or mania), such as a depressed person believing that others disapprove of him or a manic person believing that she is a supreme being
  • Mood-neutral delusions are not related to the individual’s emotional state (the beliefs are independent of mood state)

Delusional Themes

Delusional content can come in any variety; however a number of common themes for delusional content have been identified. Examples of some of the most common themes are:

Grandiose Delusions

Delusions that are characterized by fantastical beliefs that one is powerful, famous, omnipotent, or otherwise special.

Delusions of Control

This is a false belief that another person, group of people, or external force controls one’s thoughts, feelings, impulses, or behavior.

Nihilistic Delusions

A delusion whose theme centers on the nonexistence of self or parts of self, others, or the world. A person with this type of delusion may have the false belief that the world is ending.

Delusions of Religiosity

Delusions with religious or spiritual content.

Delusions of Infidelity

A delusion that one’s spouse or lover is having an affair.

Somatic Delusions

Delusions with content pertaining to bodily functioning, bodily sensations, or physical appearance.

Delusions of Guilt

The false feeling of remorse or guilt of delusional intensity.

Delusions of Reference

The false belief that insignificant remarks, events, or objects in one’s environment have personal meaning or significance.


The delusional belief that another person is in love with the deluded person.

Delusional Disorder

The current diagnostic systems used in North America (Diagnostic and Statistical Manual of Mental Disorders; DSM-IV-TR) and Europe (International Classification of Diseases; ICD-10) each recognize delusional disorder as a mental illness.

“The essential feature of Delusional Disorder is the presence of one or more nonbizarre delusions that persist for at least 1 month” (APA, 2000, p.323). Additionally, the individual must not have a symptom presentation that meets Criteria A for Schizophrenia (which means that if the individual also displays prominent auditory or visual hallucinations, disorganized speech, grossly disorganized or catatonic behavior, or so-called negative symptoms, such as flat affect, alogia, avolition, he or she will be diagnosed as having Schizophrenia as opposed to Delusional Disorder).

In addition to having delusional beliefs, the individual must not show any impairment in their functioning and their behavior must not be obviously odd or bizarre, their delusions must not be a result of any mood episodes (depression or mania), and the delusions must not be due to the direct effects of a substance (drugs, alcohol, medication) or a medical condition. Individuals with these symptoms or bizarre delusions are typically diagnosed with having another psychotic disorder, usually Schizophrenia.

The DSM-IV-TR recognizes various types of delusions based on their theme or content (p. 329):

  • Erotomanic: delusions that another person, usually of a higher status, is in love with the individual
  • Grandiose: delusions of inflated worth, power, knowledge, identity, or special relationship to a deity or famous person
  • Jealous: delusions that the individual’s sexual partner is unfaithful
  • Persecutory: delusions that the person (or someone to whom the person is close) is being malevolently treated in some way
  • Somatic: delusions that the person has some physical defect or general medical condition


Delusional Disorder is relatively rare and accounts for about 1-2% of admissions to inpatient psychiatric facilities. The prevalence rate in the general population has been estimated to be approximately 0.03%, with the lifetime morbidity risk ranging between 0.05% and 0.1%.


Delusional Disorder is difficult to treat for a number of reasons, not the least of which is that the individual truly believes that their delusions are true and so are not typically motivated for treatment, with denial being a major obstacle.

There appears to be growing evidence for the effectiveness of various antipsychotic agents in treating Delusional Disorder; however, randomized, controlled trials are still relatively lacking in this area.

Supportive therapies and Cognitive Behavioral Therapy can be helpful for individuals with Delusional Disorder but the vast majority of treatment literature in this area indicates that these types of treatments alone (that is, without accompanying antipsychotic agents) have limited utility for Delusional Disorder.

Professional Resources

Mullen, R., & Linscott, R. J. (2010). A comparison of delusions and overvalued ideas. The Journal of Nervous and Mental Disease, 198, 35-38.

Medscape Reference: Delusional Disorder

Photo courtesy of The American Psychiatric Association