DSM-IV-TR currently defines delusional disorder with the following criteria:
* Criterion A: One or more nonbizarre (ie, involving situations that could occur in real life) delusion(s) is present for at least 1 month.
* Criterion B: Criterion A for schizophrenia has never been met. (Auditory and visual hallucinations may be present but are not prominent, while tactile and olfactory hallucinations often are present if related to the delusional theme.)
* Criterion C: Apart from the impact of the delusion, functioning is not impaired markedly, and behavior is not obviously bizarre.
* Criterion D: Mood episodes that may have occurred are relatively brief relative to the delusional periods.
* Criterion E: The disturbance is not due to the direct effects of a substance or a general medical condition.
* Subtypes are defined, including erotomanic, grandiose, jealous, persecutory, somatic, mixed, and unspecified.
Epidemiological study regarding delusional disorder is difficult because of a number of factors. Although thought to be relatively uncommon, delusional disorder is not a rare condition. Diagnostic definitions historically have been poorly defined, and patients with the diagnosis rarely seek psychiatric help. The following epidemiological information is commonly accepted:
* Prevalence is low but not rare and is estimated at 0.025?0.03%, clearly different than generally accepted prevalence rates for schizophrenia (1%) or mood disorders (5%). Delusional disorder may account for 1-2% of admissions to inpatient psychiatric hospitals.
* Age at onset ranges from 18-90 years, with a mean age of 40 years.
* More females than males are represented in most samples (male-to-female ratio is ~0.85:1), but the difference is less than in mood disorders (male-to-female ratio is ~0.5:1).
* The presence of the disorder is associated with being married and employed, recent immigration, and low socioeconomic status.
* The natural course is considered variable, with improvement of delusional symptoms in 10%, remission in 33-50%, and persisting symptoms in 30-40% of cases. Onset can be acute or progressive. Patients with the acute and jealous subtypes may have a better prognosis.
* Familial transmission is suspected and comorbidity is not uncommon.
* Significant diagnostic overlap exists with paranoid personality disorder, although long-term studies indicate that delusional disorder is a distinct entity when compared with depression and schizophrenia. Data suggest that among patients diagnosed with delusional disorder, less than 25% are later reclassified as schizophrenic and less than 10% are later diagnosed with a mood disorder.
* The literature suggests that most paranoid or delusional presentations are not the result of schizophrenia or delusional disorder but, rather, the result of other conditions, including substance-associated syndromes and medical conditions.
ETIOLOGY
The cause per se is unknown. Delusional disorder theoretically represents a heterogeneous group of conditions that seems distinct from mood disorders and schizophrenia. Family studies show increased prevalence of delusional disorder and paranoid personality traits in relatives of delusional disorder probands but no association with mood disorders or schizophrenia. Longitudinal studies suggest that the disorder is stable and reclassified as a mood disorder or other psychotic disorder only 10-25% of the time.
Biological
Delusions can be a feature of a number of biological conditions, suggesting possibly biologic underpinnings for the disorder. Most commonly, neurological lesions associated with the temporal lobe, limbic system, and basal ganglia are implicated in delusional syndromes. Neurological observations indicate that delusional content is influenced by the extent and location of brain injury. Prominent cortical damage often leads to simple, poorly formed, persecutory delusions. Lesions of the basal ganglia elicit less cognitive disturbance and more complex delusional content. Right posterior cerebellar lesions are associated with misidentification syndromes. Excessive dopaminergic and reduced acetyl cholinergic activity have been linked to the formation of delusional symptoms.
Psychological
Psychological explanations of delusions present 3 ways of viewing the phenomena of delusions.
* Delusions as defensive: Sigmund Freud proposed that delusions serve a defensive function and protect the patient from intrapsychically unacceptable homosexual impulse through the use of reaction formation, projection, and denial.
* Delusions as the result of cognitive defects: In the 1950s, Eilhard von Domarus emphasized the use of flawed logic in the manufacturing of delusions. Patients are observed to accept ideas with too little evidence for their conclusions.
* Delusions as the result of abnormal perceptual experience: In the 1970s, Brendan Maher described delusions stemming from abnormal perceptual experience due to central nervous system (CNS), peripheral nervous system, or environmental cues. Delusions were described as created to deal with these abnormal phenomena.
Social/other
Norman Cameron defined social situations with the following characteristics as contributing to the development of delusional disorder: expectations of receiving sadistic treatment, distrust and suspicion, social isolation, jealousy, lowered self-esteem, people seeing their own defects in others, and rumination over meaning and motivation.
Associated risk factors that suggest other avenues in the pathogenesis of delusions include advanced age, social isolation, group delusions (eg, in the McCarthy era), low socioeconomic status, premorbid personality disorder, sensory isolation (particularly deafness), recent immigration, family transmission, head injury, and substance abuse disorders.