Symptoms and diagnosis of delusional disorder

What is delusional disorder

Delusional disorder is an unusual mental illness, characterised primarily by one or more delusions that significantly affect the patient’s thinking and behaviour.

One of the distinguishing features of this disorder is the absence of hallucinations or other significant psychiatric symptoms. This is where it differs most from schizophrenia.

In addition to delusions, people with schizophrenia experience a number of other symptoms, including hallucinations, thought disorders, and catatonia, whereas people with delusional disorder primarily experience delusions.

Delusions in delusional disorder are usually about things that are unlikely, but not completely impossible.

For example, a person may believe that they are a special person, or they may be convinced that a special imagined event will happen to them. These delusions often have a significant impact on the person’s daily life and can sometimes cause serious problems.

Outside of their delusions, however, people with delusional disorder generally maintain normal social and occupational functioning. Their behaviours and reactions are mostly routine, and their relationships with others are generally normal.

Because of these characteristics, delusional disorders often go undetected in the early stages. The person’s loved ones may dismiss their unusual beliefs as just their own special ideas.

Finally, the exact cause of delusional disorders is still unknown. Several factors are thought to be involved, including genetics, biochemical changes, and environmental factors, but no definitive research or evidence has yet been presented.

Signs and symptoms

Delusional disorders are characteristically based on one or more delusional beliefs. These delusions may sometimes differ from common sense, and the sufferer has a firm belief that they are real.

Delusions are characterised by

Manifestations of stubbornness and strength

The patient refuses to give up their beliefs, even when presented with evidence to the contrary. This indicates an unusual level of persistence, which may sometimes appear to be inconsistent with reality.

Changes in routine

The patient’s daily routine may be heavily influenced by their delusional beliefs and lose its reality.

Doubt and sensitivity

Patients often lack a sense of humour and may show excessive sensitivity, especially where their beliefs are concerned. They are often very sensitive to any questioning or criticism of their ideas or beliefs.


Patients often feel that they are the centre of the world.

They may believe that everything that happens around them is related to them.

Delusional disorder has the following additional characteristics

Primary disorder

This means that the delusions do not appear as a result of another mental illness, but rather occur independently.

Stable disorder

The patient shows a very strong preoccupation with their delusions, which means that their thoughts or beliefs do not change over time.


Delusional disorders can persist for a long period of time, and in some patients may last a lifetime.


Delusional disorder is defined in the American Psychiatric Association’s (APA) DSM-Ⅳ-TR as follows.

Patients experience realistic delusions about situations that are likely to occur in everyday life, such as thinking they are being followed or believing they have a physical problem.

These delusions are distinct from the symptoms of other conditions, such as schizophrenia.

However, they may experience sensory hallucinations associated with the delusions, such as the sensation of something crawling on their skin.

The person’s daily functioning is usually preserved, and their behaviour does not appear unusual.

However, sometimes depression or other mood symptoms associated with the delusions may also occur.

However, these mood symptoms last for a relatively short period of time in the person’s overall symptom duration.

The condition is not caused by medication or other medical factors.

And patients can experience several different types of delusions.

For example, in nymphomania, patients believe there is a high-status figure who loves them. In megalomania, patients believe they have special abilities or knowledge. In jealousy, patients are convinced their partner is having an affair.

In victimisation, the patient believes they are being harmed by someone. In somatoform, the patient believes there is something wrong with their body.

Some patients may experience multiple types of delusions, but if none of them are prominent, they are said to be mixed.

And patients who experience delusions that do not fit neatly into a specific type are classified as unspecified.


The cause of delusional disorder is not yet fully understood, but many factors are thought to be involved in its development.

Among them, a combination of genetic, biochemical, and environmental factors are thought to play a role.

In particular, some patients have an imbalance of neurotransmitters, which play an important role in sending and receiving messages within the brain.

The relationship between delusional disorder and schizophrenia has also been studied, with recent research suggesting that the two disorders may be classified within the same disease spectrum, with the main difference being that delusional disorder has less severe symptoms and functional impairment than schizophrenia.

A number of risk factors have been suggested for the development of delusional disorder, including family history, severe stress, low socioeconomic status, substance abuse, immigration, marriage, employment, single status in men, and widowed women.

Delusional disorder is a relatively under-diagnosed illness in clinical practice.

This is due to the nature of the patient’s symptoms and the difficulty in recognising the illness by themselves and those around them as they usually maintain good social functioning.

Delusional disorder tends to develop or be diagnosed after the age of 30 or 40. It is also known that the illness is diagnosed more often in women than in men.

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