Delusional disorder

Delusional disorder
Other names	Delusional insanity,[1] paranoia[citation needed]
Painting by Théodore Géricault portraying an old man with a grandiose delusion of power and military command. Grandiose delusions are common in delusional disorder.
Specialty	Psychiatry, clinical psychology
Symptoms	Strong false belief(s) despite superior evidence to the contrary
Usual onset	18–90 years old (mean of about age 40)[2]
Types	Erotomanic type, grandiose type, jealous type, persecutory type, somatic type, mixed type, unspecified type
Causes	Genetic and environmental[3]
Risk factors	Family history, chronic stress, low SES, substance abuse
Differential diagnosis	Paranoid personality disorder, manic-depressive illness, schizophrenia, substance-induced psychosis[3]
Frequency	0.02-0.1% of general population [4][5]

Delusional disorder, traditionally synonymous with paranoia, is a mental illness in which a person has delusions, but with no accompanying prominent hallucinations, thought disorder, mood disorder, or significant flattening of affect.^[6][7] Delusions are a specific symptom of psychosis. Delusions can be bizarre or non-bizarre in content;^[7] non-bizarre delusions are fixed false beliefs that involve situations that could occur in real life, such as being harmed or poisoned.^[8] Apart from their delusion or delusions, people with delusional disorder may continue to socialize and function in a normal manner and their behavior does not necessarily seem odd.^[9] However, the preoccupation with delusional ideas can be disruptive to their overall lives.^[9]

For the diagnosis to be made, auditory and visual hallucinations cannot be prominent, though olfactory or tactile hallucinations related to the content of the delusion may be present.^[7] The delusions cannot be due to the effects of a drug, medication, or general medical condition, and delusional disorder cannot be diagnosed in an individual previously properly diagnosed with schizophrenia. A person with delusional disorder may be high functioning in daily life. Recent and comprehensive meta-analyses of scientific studies point to an association with a deterioration in aspects of IQ in psychotic patients, in particular perceptual reasoning, although, the between-group differences were small.^[10][11][12]

According to German psychiatrist Emil Kraepelin, patients with delusional disorder remain coherent, sensible and reasonable.^{[13] [dubious – discuss]} The Diagnostic and Statistical Manual of Mental Disorders (DSM) defines six subtypes of the disorder: erotomanic (belief that someone is in love with one), grandiose (belief that one is the greatest, strongest, fastest, richest, or most intelligent person ever), jealous (belief that one is being cheated on), persecutory (delusions that one or someone one is close to is being malevolently treated in some way), somatic (belief that one has a disease or medical condition), and mixed, i.e., having features of more than one subtype.^[7]

Delusions also occur as symptoms of many other mental disorders, especially the other psychotic disorders.

The DSM-IV and psychologists agree that personal beliefs should be evaluated with great respect to cultural and religious differences, as some cultures have normalized beliefs that may be considered delusional in other cultures.^[14]

An earlier, now-obsolete, nosological name for delusional disorder was "paranoia". This should not be confused with the modern definition of paranoia (i.e., persecutory ideation specifically).