Delusional disorders involve bizarre delusions, in which a person cannot distinguish between what is real and what is imagined. A person suffering from delusional disorder often fights for their right to believe the absurd, radically embracing their delusion.
Previously referred to as paranoid disorder, a delusional disorder is a serious mental illness, also known as a psychosis. Delusional disorder becomes a diagnosed condition when an individual displays one or more delusions for a month or longer. Delusional disorders tend to be extreme, often composed of implausible beliefs that do not change, despite the presence of conflicting evidence. Delusional disorders are equally likely to occur in males and females.
With a delusional disorder, delusions involving persecution are not uncommon—for example, the belief that a monitoring device has been implanted in one’s body. Delusional disorder symptoms can also encompass erotomania, in which a person believes a celebrity or complete stranger is in love with them. Attempting rational communication with someone who suffers from a delusional disorder can be ineffective and frustrating.
Distinct from schizophrenia, delusional disorders are a separate psychosis. Routine functioning generally is not impaired, and behavior is not affected except for the delusional disorder symptoms. Delusional disorder treatment includes psychotherapy and prescription medications. The goal of a medical professional is to establish a therapeutic alliance with a person with a delusional disorder.
Sources: Psych Central