The cause of delusional disorder is not known. Some studies suggest a biological component due to increased prevalence in first degree relatives of individuals with the disorder.
Non-bizarre delusions including feelings of being followed, poisoned, infected, deceived or conspired against, or loved at a distance. Non-bizarre referred to real life situations which could be true, but are not or are greatly exaggerated. Bizarre delusions, which would rule out this disorder, are those such as believing that your stomach is missing or that aliens are seeking you out to be their leader. Delusional disorder can be subtyped into the following categories: erotomanic, grandiose, jealous, persecutory (most common), somatic, and mixed.
Medications can be helpful but are often refused due to the nature of the disorder. Some individuals function quite normally, while others may react to their delusion in ways that can greatly disrupt their life.
Ranges from good to very poor depending on the individual, subtype, and life circumstances.