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Delusional disorder is an uncommon psychiatric condition in which patients present with non-bizarre delusions, but with no accompanying prominent hallucinations, thought disorder, mood disorder, or significant flattening of affect. Delusions are a type of psychotic symptom. Non-bizarre delusions are fixed false beliefs that involve situations that could potentially occur in real life; examples include being followed or poisoned. Apart from their delusions, people with delusional disorder may continue to socialize and function in a normal manner and their behaviour does not generally seem odd or bizarre. However, the preoccupation with delusional ideas can be disruptive to their overall lives. 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.
To be diagnosed with delusional disorder, the delusion or 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 diagnosed with schizophrenia. A person with delusional disorder may be high functioning in daily life, and this disorder bears no relation to one's IQ. According to German psychiatrist Emil Kraepelin, patients with delusional disorder remain coherent, sensible and reasonable. The Diagnostic and Statistical Manual of Mental Disorders (DSM) defines six subtypes of the disorder characterized as erotomanic (believes that someone is in love with him or her), grandiose (believes that he/she is the greatest, strongest, fastest, richest, and/or most intelligent person ever), jealous (believes that the love partner is cheating on him/her), persecutory (believes that someone is following him/her to do some harm in some way), somatic (believes that he/she has a disease or medical condition), and mixed, i.e., having features of more than one subtype. Delusions also occur as symptoms of many other mental disorders, especially the other psychotic disorders.
The DSM-IV, and psychologists, generally agree that personal beliefs should be evaluated with great respect to complexity of cultural and religious differences since some cultures have widely accepted beliefs that may be considered delusional in other cultures.
Indicators of a delusion 
The following can indicate a delusion:
- The patient expresses an idea or belief with unusual persistence or force.
- That idea appears to exert an undue influence on the patient's life, and the way of life is often altered to an inexplicable extent.
- Despite his/her profound conviction, there is often a quality of secretiveness or suspicion when the patient is questioned about it.
- The individual tends to be humorless and oversensitive, especially about the belief.
- There is a quality of centrality: no matter how unlikely it is that these strange things are happening to him, the patient accepts them relatively unquestioningly.
- An attempt to contradict the belief is likely to arouse an inappropriately strong emotional reaction, often with irritability and hostility.
- The belief is, at the least, unlikely, and out of keeping with the patient's social, cultural and religious background.
- The patient is emotionally over-invested in the idea and it overwhelms other elements of their psyche.
- The delusion, if acted out, often leads to behaviors which are abnormal and/or out of character, although perhaps understandable in the light of the delusional beliefs.
- Individuals who know the patient observe that the belief and behavior are uncharacteristic and alien.
The following features are found:
- It is a primary disorder.
- It is a stable disorder characterized by the presence of delusions to which the patient clings with extraordinary tenacity.
- The illness is chronic and frequently lifelong.
- The delusions are logically constructed and internally consistent.
- The delusions do not interfere with general logical reasoning (although within the delusional system the logic is perverted) and there is usually no general disturbance of behavior. If disturbed behavior does occur, it is directly related to the delusional beliefs.
- The individual experiences a heightened sense of self-reference. Events which, to others, are nonsignificant are of enormous significance to him or her, and the atmosphere surrounding the delusions is highly charged.
Diagnosis of a specific type of delusional disorder can sometimes be made based on the content of the delusions. The Diagnostic and Statistical Manual of Mental Disorders (DSM) enumerates seven types:
- Erotomanic type (erotomania): delusion that another person, often a prominent figure, is in love with the individual. The individual may breach the law as he/she tries to obsessively make contact with the desired person.
- Grandiose type: delusion of inflated worth, power, knowledge, identity or believes himself/herself to be a famous person, claiming the actual person is an impostor or an impersonator.
- Jealous type: delusion that the individual's sexual partner is unfaithful when it is untrue. The patient may follow the partner, check text messages, emails, phone calls etc. in an attempt to find "evidence" of the infidelity.
- Persecutory type: This delusion is a common subtype. It includes the belief that the person (or someone to whom the person is close) is being malevolently treated in some way. The patient may believe that he/she has been drugged, spied-on, harassed and so on and may seek "justice" by making police reports, taking court action or even acting violently.
- Somatic type: delusions that the person has some physical defect or general medical condition
- Mixed type: delusions with characteristics of more than one of the above types but with no one theme predominating.
- Unspecified type: delusions that cannot be clearly determine or doesn't characterize in any of the categories in the specific types.
The cause of delusional disorder is unknown, but genetic, biochemical and environmental factors may play a significant role in its development. Some people with delusional disorders may have an imbalance in neurotransmitters, the chemicals that send and receive messages to the brain. There does seem to be some familial component, and social isolation, immigration (generally for persecutory reasons), drug abuse, excessive stress, being married, being employed, low socioeconomic status, celibacy among men, and widowhood among women may also be risk factors. Delusional disorders are probably unrelated to schizophrenia or mood disorders.
Delusional disorders are uncommon in psychiatric practice, though this may be an underestimation due to the fact that those afflicted lack insight and thus avoid psychiatric assessment. The prevalence of this condition stands at about 24 to 30 cases per 100,000 people while 0.7 to 3.0 new cases per 100,000 people are reported every year. Delusional disorder accounts for 1-2% of admissions to inpatient mental health facilities. The incidence of first admissions for delusional disorder is lower, from 0.001-0.003%.
Delusional disorder tends to appear in middle to late adult life, and for the most part first admissions to hospital for delusional disorder occur between age 33 and 55. It is more common in women than men, and immigrants seem to be at higher risk.
Differential diagnosis includes ruling out other causes such as drug-induced conditions, dementia, infections, metabolic disorders, and endocrine disorders. Other psychiatric disorders must then be ruled out. In delusional disorder, mood symptoms tend to be brief or absent, and unlike schizophrenia, delusions are non-bizarre and hallucinations are minimal or absent.
Interviews are important tools to obtain information about the patient's life situation and past history to help make a diagnosis. Clinicians generally review earlier medical records to gather a full history. Clinicians also try to interview the patient's immediate family, as this can be helpful in determining the presence of delusions. The mental status examination is used to assess the patient's current mental condition.
A psychological questionnaire used in the diagnosis of the delusional disorder is the Peters Delusion Inventory (PDI) which focuses on identifying and understanding delusional thinking. However, this questionnaire is more likely used in research than in clinical practice.
A challenge in the treatment of delusional disorders is that most patients have limited insight, and do not acknowledge that there is a problem. Most patients are treated as out-patients, although hospitalization may be required in some cases if there is a risk of harm to self or others. Individual psychotherapy is recommended rather than group psychotherapy, as patients are often quite suspicious and sensitive. Antipsychotics are not well tested in delusional disorder, but they do not seem to work very well, and often have no effect on the core delusional belief. Pimozide may be more effective than other agents. Antipsychotics may be more useful in managing agitation that can accompany delusional disorder.
Psychotherapy for patients with delusional disorder can include cognitive therapy which is conducted with the use of empathy. During the process, the therapist can ask hypothetical questions in a form of therapeutic Socratic dialogue. This therapy has been mostly studied in patients with the persecutory type. The combination of pharmacotherapy with cognitive therapy integrates treating the possible underlying biological problems and decreasing the symptoms with psychotherapy as well. Psychotherapy has been said to be the most useful form of treatment because of the trust formed in a patient and therapist relationship. The therapist is there for support and must not show any signs implying that the patient is mentally ill.
Supportive therapy has also been shown to be helpful. Its goal is to facilitate treatment adherence and provide education about the illness and its treatment.
Furthermore, providing social skills training has helped many persons. It can promote interpersonal competence as well as confidence and comfort when interacting with those individuals perceived as a threat.
Insight-oriented therapy is rarely indicated or contraindicated; yet there are reports of successful treatment. Its goals are to develop therapeutic alliance, containment of projected feelings of hatred, impotence, and badness; measured interpretation as well as the development of a sense of creative doubt in the internal perception of the world. The latter requires empathy with the patient's defensive position.
See also 
- Semple.David."Oxford Hand Book of Psychiatry" Oxford Press. 2005. p 230
- Hales E and Yudofsky JA, eds, The American Psychiatric Press Textbook of Psychiatry, Washington, DC: American Psychiatric Publishing, Inc., 2003
- Winokur, George."Comprehensive Psychiatry-Delusional Disorder"American Psychiatric Association. 1977. p 513
- American Psychiatric Association. (2000). Diagnostic and Statistical Manual of Mental Disorders, (4th ed., text revision). Washington, DC: American Psychiatric Association.
- Winokur, G. (1977). Delusional Disorder (Paranoia). Comprehensive Psychiatry, 18(6), 513. Retrieved March 17, 2012, from <http://resolver.scholarsportal.info.myaccess.library.utoronto.ca/resolve/0010440x/v18i0006/511_dd>
- Winokur, G. (1977). Delusional Disorder (Paranoia). Comprehensive Psychiatry, 18(6), 511. Retrieved March 17, 2012, from http://journals1.scholarsportal.info.myaccess.library.utoronto.ca/tmp/1230440208560715363.pdf
- Shivani Chopra. Delusional Disorder. eMedicine.
- Munro, Alistair (1999). Delusional disorder: paranoia and related illnesses. Cambridge, UK: Cambridge University Press. ISBN 0-521-58180-X.
- http://www.health.am/psy/delusional-disorder Delusional Disorder. Retrieved 7 August 2012
- "Causes of Delusional Disorder". Retrieved 2010-08-06.
- Kay DWK. “Assessment of familial risks in the functional psychoses and their application in genetic counseling. Br J Pschychiatry." 1978. p385-390
- Karakus,Gonca.”Delusional Parasitosis: Clinical Features, Diagnosis and Treatment”American Psychiatric Association. 2010.p396
- Shivani Chopra, MD; Chief Editor et al. "Delusional Disorder - Epidemiology - Patient demographics". Retrieved 2013-04-15.
- Crowe, R. R., & Roy, M. A. (2008). Delusional disorders. In S. H. Fatemi & P. J. Clayton (Eds.), The Medical Basis of Psychiatry (pp. 125-131). New York, USA: Humana Press.
- "Demography of paranoid psychosis (delusional disorder): a review and comparison with schizophrenia and affective illness.". Arch Gen Psychiatry 39 (8): 890–902. Aug 1982. doi:10.1001/archpsyc.1982.04290080012003.
- "Delusional Disorders:Treatment". Retrieved 2010-08-06.
- "Treatments". Retrieved 2010-08-06.
- Grohol, John. "Delusional Disorder Treatment". Psych Central. Retrieved 24 November 2011.
- Shivani Chopra, MD; Chief Editor. "Delusional Disorder - Treatment & Management - Psychotherapy". Medscape reference. Retrieved 2013-04-15.
Further reading 
- Munro, A. (1999) Delusional Disorder: Paranoia and Related Illnesses. Cambridge: Cambridge University Press. ISBN 0-521-58180.
- Sims, A. (1995) Symptoms in the mind: An introduction to descriptive psychopathology. Edinburgh: Elsevier Science Ltd. ISBN 0-7020-2627-1.
- American Psychiatric Association. (2000). Diagnostic and Statistical Manual of Mental Disorders, (4th ed., text revision). Washington, DC: American Psychiatric Association. ISBN 978-0-89042-024-9