delusion disorder

What is delusional disorder?

Delusion is a strong fixed false belief which did not have any relation with delusional disorder sufferer’s educational and cultural background.

Delusions can also present in schizophrenia and other psychotic disorder. But delusional disorders are quiet different from delusions. Because in delusional disorder, the beliefs are non bizarre, that means the beliefs hold by the patient can occur in real life such as being followed, poisoned, infected etc. Moreover, patient with delusional disorder less experience hallucinations and most probably they experience olfactory hallucination (to smell something that is not experienced by others) and tactile hallucination (patient experience that insect is crawling inside their skin or outside the skin but not seen by others or any medical examination). To know more about behavior of patient with delusional disorder, I would like to include one case of Mrs. A.

She was haunted by persecutory ideas that, her daughter in law will put poison in her food. Moreover she thought that daughter in law is turning her son against her. These are the persecutory ideas hold by Mrs. A, and it was the psycho-pathological part of Mrs. A.  But her hygiene, cognitive functioning, and to stay alone in home were not affected by delusional disorder.

From this example we can understand that the patient with delusional disorder can remain away from clinical attention and it is not an easy task to identify delusional beliefs in a patient. Nevertheless, there are some useful techniques which are useful in identifying and understanding delusional disorder.

Techniques are clinical interview in which therapist took interview to obtain information related to patient’s past life incidents and other technique is to conduct mental status examination of the patient. We can also use the Peter Delusion Inventory (PDI), which focuses on identifying and understanding delusional disorder.


  • If the patient have some beliefs that can occur in real life (such as being followed or poisoned) for at least 3 months.
  • Absence of strange behavior (which can be seen in other psychotic disorder like schizophrenia).
  • The disturbance in the patient should not be due to the direct physiological effects of a substance (drug of abuse or medication) or a general medical condition.
  • There will be no persistent hallucinations.

Delusion can be grouped according to the following main themes: –

  • Persecutory Type are most commonly concerned with persons or organizations who are thought to be trying to harm on the patient, damage his or her reputation make him or her insane or poison him or her. Such delusions are common in Schizophrenia and in severe affective disorders.
  • Grandiose Type is beliefs of exaggerated self importance. The patient may think himself or herself to be wealthy or a special person; occurs in mania and schizophrenia
  • Somatic Type is concern with illness. The patient may believe wrongly and in the face of all medical evidence to the contrary that he or she is ill; found in elderly.
  • Jealous Type is more common among men. They follow there spouse to spy on her examine her clothes or search her bags.
  • Erotomanic Type is rare and occurs more in women. A woman believes that she is loved by a man who is usually inaccessible, of higher social status and whom she has never spoken.
  • Mixed Type in this type patient experience more than one delusional theme.
  • Unspecified Type this type is reserved for cases in which the predominant delusion cannot be sub typed with in the previous categories. (For Example, Nihilistic delusional disorder; patent experience that they have lost not only their possessions, status and strength, but also their heart, blood and intestines)


Clear cut identification of causes behind delusional disorders are very challenging. Nevertheless, there are some research finding showed the role of genetic or biological element in the cause of delusional disorder and another cause behind delusional disorder is medical causes like, neurodegenerative disorders (e.g., Alzheimer’s disease) brain tumors, Hyper tension ,vascular disease, metabolic and endocrinal causes (e.g., hypocalcaemia, hyperthyroidism etc), vitamin deficiencies, medications (e.g., corticosteroids), substances ( e.g., cocaine, alcohol) and toxins (e.g., mercury).

Moreover dysfunctions in the cognitive processing also lead to delusional disorder. There is a chance for delusion to arise when people used to explain their life in distorted way. Mainly these people develop assumptions and opinions about others with few evidence and hold negative attitude toward life events. And these behavior and perception toward others lead patient to develop delusional believes in them.

Differential diagnosis of delusional disorder

To do differential diagnosis in delusional disorder, first of all we have to separate the medicine induced conditions, dementia, infections, metabolic disorder, and endocrine disorders. After that we have to separate other psychiatric disorders and they are given below: –

  1. In delusional disorder, delirium (acute confusional state, result in attention deficit, changes in arousal etc.) and dementia (gradual decrease in the ability to think and remember), can also differentiated by the presence of a fluctuating level of consciousness or impaired cognitive abilities.
  2. Delusional disorder is differentiated from schizophrenia by the absence of other schizophrenic symptoms and by the non bizarre quality of the delusions. Because patient with delusional disorder also lack the impaired functioning seen in schizophrenia.
  3. The somatic type of delusional disorder may resemble a depressive disorder or a somatoform disorder. The somatic type of delusional disorder is differentiated from depressive disorders by the absence of other signs of depression and the lack of a pervasive quality to the depression.
  4. Delusional disorder can be differentiated from somatoform disorders by the degree to which the somatic belief is held by the patient. Patients with somatoform disorder allow for the possibility that their disorder doesn’t exist, whereas patients with delusional disorder do not doubt its reality.
  5. Separating paranoid personality delusional disorder requires sometimes difficult clinical distinction between extreme suspiciousness and frank delusion.

In general, if clinicians doubt that a symptom is a delusion, the diagnosis of a delusional disorder should not be made.


Finally we can use different tools to obtain information about the patient’s life situation and past history. Generally, clinical interviews are used to obtain information about patient’s life situation and past history. In clinical interview both patient and family have to cooperate. And the information from both were kept separate to make diagnosis easy. Mental status examination of the patient also a very useful tool to make diagnosis and provides current mental condition of the patient. Peter’s Delusional Inventory (PDI) is another tool to identify and understand delusional thinking. The other psychiatric scales are also use to assess delusional level, such as Brief Psychiatric Rating Scale (BPRS) and Positive and Negative Symptoms of Schizophrenia (PANSS).

Finally I would like to include some treatment technique used in delusional disorders. They are psychotherapy and Socratic questioning. Through Socratic questioning (questions using what, why, when, where etc.) we can put some doubts in patient’s delusional beliefs. There by we can decrease the strength of patient’s delusional beliefs. In psychotherapy we can use cognitive therapy. Through using cognitive therapy, we can list out the error believes of patient. Then we can request the patient to rethink about their error beliefs and suggest them to think error beliefs in different way.


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