MHADD

Mental Health and Delusional Disorder:
Delusional disorder, previously called 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 main feature of this disorder is the presence of delusions, which are unshakable beliefs in something untrue. People with delusional disorder experience non-bizarre delusions, which involve situations that could occur in real life, such as 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 often can continue to socialize and function normally, apart from the subject of their delusion, and 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.
Although delusions might be a symptom of more common disorders, such as schizophrenia, delusional disorder itself is rather rare. Delusional disorder most often occurs in middle to late life and is slightly more common in women than in men.