Delusional disorder is characterized by firmly held false beliefs (delusions) that persist for at least 1 month, without other symptoms of psychosis. Diagnosis is by psychiatric assessment. Treatment is with psychotherapy and sometimes antipsychotic medications.
The distinction between delusions and mistaken beliefs is that delusional beliefs remain unchanged in the face of clear, reasonable evidence to the contrary. This distinction is sometimes difficult to make when the beliefs are plausible (eg, that a spouse is unfaithful).
Delusional disorder is distinguished from schizophrenia by the presence of delusions without any other symptoms of psychosis (eg, prominent hallucinations, disorganized speech or behavior, negative symptoms) and without any marked functional impairment apart from that associated with the delusion (1). Diagnostic criteria for this disorder also require that delusions not be caused by another medical condition or a substance. The delusions may be either
Nonbizarre: They involve situations that could occur, such as being followed, poisoned, infected, loved at a distance, or deceived by one’s spouse or lover.
Bizarre: They involve implausible situations, such as believing that someone removed their internal organs without leaving a scar.
In contrast to schizophrenia, delusional disorder is relatively uncommon (2). Onset is generally involutional, meaning that it occurs in middle or late adult life. Psychosocial functioning is not as impaired as it is in schizophrenia, and impairments usually arise directly from the delusional belief.
When delusional disorder occurs in older adults, it is sometimes called paraphrenia. It may coexist with mild dementia. The clinician must be careful to distinguish delusions from elder abuse being reported by an older adult with mild dementia.
References
1. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition Text Revision, DSM-5-TR (DSM-5-TR). American Psychiatric Association Publishing, Washington, DC, 2022, pp 105-109.
2. Lieberman JA, First MB.. Psychotic Disorders. N Engl J Med. 2018;379(3):270-280. doi:10.1056/NEJMra1801490
Symptoms and Signs of Delusional Disorder
Delusional disorder may arise from a preexisting paranoid personality disorder. In such people, a pervasive distrust and suspiciousness of others and their motives begin in early adulthood and extend throughout life.
Early symptoms may include the feeling of being exploited, preoccupation with the loyalty or trustworthiness of friends, a tendency to read threatening meanings into benign remarks or events, persistent bearing of grudges, and a readiness to respond to perceived slights.
Several subtypes of delusional disorder with varying symptoms are recognized:
Erotomanic: Patients believe that another person is in love with them. Efforts to contact the object of the delusion through telephone calls, letters, surveillance, or stalking are common. People with this subtype may have conflicts with the law related to this behavior.
Grandiose: Patients believe they have a great talent or have made an important discovery.
Jealous: Patients believe that their spouse or sexual partner is unfaithful. This belief is based on incorrect inferences supported by dubious evidence. Patients may resort to physical assault.
Persecutory: Patients believe that they are being plotted against, spied on, maligned, or harassed. They may repeatedly attempt to obtain justice through appeals to courts and other government agencies and may resort to violence in retaliation for the imagined persecution.
Somatic: The delusion relates to a bodily function; eg, patients believe they have a physical deformity, odor, or parasite.
Patients' behavior is not obviously bizarre or odd, and apart from the possible consequences of their delusions (eg, social isolation or stigmatization, marital or work difficulties), patients' functioning is not markedly impaired.
Diagnosis of Delusional Disorder
Psychiatric assessment
Diagnostic and Statistical Manual of Mental Disorders, 5th edition, Text Revision (DSM-5-TR) criteria
General medical evaluation to exclude other etiologies
Diagnosis depends largely on making a clinical assessment, obtaining a thorough history, and ruling out other specific conditions associated with delusions (eg, substance use, Alzheimer disease, epilepsy, obsessive-compulsive disorder, delirium, other schizophrenia spectrum disorders).
Diagnosis of delusional disorder itself requires the following (1):
Presence of at least 1 delusion for at least 1 month
Never having met the preceding criterion for schizophrenia
No significant functional impairment or obviously bizarre behavior
No significant mood episodes (ie, manic or depressive episodes are relatively brief when compared to the duration of delusional periods)
Exclusion of general medical conditions, substance use disorder, or another mental disorder as the cause of the disturbance
Assessment of whether patients might be a danger to themselves or others is very important, especially the extent to which patients are willing to act on their delusion.
Diagnosis reference
1. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition Text Revision, DSM-5-TR (DSM-5-TR). American Psychiatric Association Publishing, Washington, DC, 2022, pp 105-109.
Treatment of Delusional Disorder
Establishment of an effective clinician-patient relationship
Management of complications
Sometimes antipsychotics
Treatment aims to establish an effective clinician-patient relationship and to manage complications. Patients' substantial lack of psychological insight is a challenge to treatment.
If patients are assessed to be dangerous, hospitalization may be required.
Insufficient data are available to support the use of any particular medication, although antipsychotics sometimes alleviate symptoms (1).
A long-term treatment goal of shifting the patient’s major area of concern away from the delusional locus to a more constructive and gratifying area is difficult but reasonable.
Treatment reference
1. Muñoz-Negro JE, Cervilla JA. A Systematic Review on the Pharmacological Treatment of Delusional Disorder. J Clin Psychopharmacol. 2016;36(6):684-690. doi:10.1097/JCP.0000000000000595
Prognosis for Delusional Disorder
Delusional disorder does not usually lead to severe impairment or change in personality, but delusional concerns may gradually progress. Most patients can remain employed as long as their work does not involve matters related to their delusions.
