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Delusional disorder or paranoid disorder

Delusional disorder or paranoid disorder, is a type of serious mental illness called a psychosis in which a person cannot tell what is real from what is imagined.

The mental health charity Mind says someone with delusional disorder is likely to have a complex,  paranoid but untrue idea that puts them in conflict with those around them.

The person is likely to feel persecuted and more likely to seek help from a lawyer or the police than from a mental health professional.


People with delusional disorder may believe they are being followed, poisoned, deceived, conspired against or loved from a distance. These delusions usually involve the misinterpretation of perceptions or experiences. In reality, however, the situations are either not true at all or highly exaggerated.

People with delusional disorder can often continue to socialise and function normally and, apart from with the subject of their delusion, generally do not behave in an obviously odd or bizarre manner. This is unlike people with other psychotic disorders, who also might have delusions as a symptom of their disorder. In some cases, however, people with delusional disorder might become so preoccupied with their delusions that their lives are disrupted.

Delusional disorder is more common in middle to late life and is slightly more common in women than it is in men.

Treatment and management of delusional disorder is covered by NHS guidance for mental health disorders related to schizophrenia. A clinical diagnosis of psychosis is common in people with substance misuse. The National Institute for Health and Clinical Excellence (NICE) says around 40% of people with psychosis misuse substances at some point in their life.

Symptoms of delusional disorder

Delusions are the most obvious symptom of this disorder. A person might also be irritable, angry or sad.

They may experience hallucinations - seeing, hearing, smelling or feeling things that are not really there.

There are several different traits a person with delusional disorder may display:

  • De Clerambault syndrome (erotomania): Someone with this type of delusional disorder believes that another person, often someone important or famous, is in love with them. The person might attempt to contact the object of the delusion and stalking behaviour is not uncommon.
  • Grandiose: A person with this type of delusional disorder has an over-inflated sense of worth, power, knowledge or identity. The person might believe they have a great talent or have made an important discovery.
  • Jealous: A person with this type of delusional disorder believes that their spouse or sexual partner is unfaithful.
  • Persecutory: People with this type of delusional disorder believe that they (or someone close to them) are being mistreated, or that someone is spying on them or planning to harm them. It is not uncommon for people with this type of delusional disorder to make repeated complaints to legal authorities.
  • Somatic: A person with this type of delusional disorder believes that they have a physical defect or medical problem. This includes delusional parasitosis – a belief that insects are crawling over them or they have bugs under the skin.
  • Mixed: People with this type of delusional disorder have two or more of the types of delusions listed above. They may also have a shared delusion with another person, known as folie à deux.

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