Delusional disorder is a psychiatric diagnosis denoting a mental illness that involves holding one or more non-bizarre delusions in the absence of any other significant psychopathology (signs or symptoms of mental illness). In particular a person with delusional disorder has never met any other criteria for schizophrenia and does not have any marked hallucinations, although tactile (touch) or olfactory (smell) hallucinations may be present if they are related to the theme of the delusion.
A person with delusional disorder can be quite functional and does not tend to show any odd or bizarre behaviour except as a direct result of the delusional belief.
It is worth noting that the term paranoia was previously used in psychiatry to denote what is now called 'delusional disorder'. The modern psychiatric use of the word paranoia is subtly different but now rarely refers to this specific diagnosis.
Delusional disorder may typically be one of the following types:
- Erotomanic Type (see erotomania): delusion that another person, usually of higher status, is in love with the individual.
- Grandiose Type: delusion of inflated worth, power, knowledge, identity, or special relationship to a deity or famous person (e.g. see Jerusalem syndrome)
- Jealous Type: delusion that the individual's sexual partner is unfaithful (see delusional jealousy).
- Persecutory Type: delusion that the person (or someone to whom the person is close) is being malevolently treated in some way.
- Somatic Type: delusions that the person has some physical defect or general medical condition (for example, see delusional parasitosis).
- A diagnosis of 'mixed type' or 'unspecified type' may also be given if the delusions fall into several or none of these categories.
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