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, unshakable beliefs in something untrue or not based on reality. People with delusional disorder generally 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. If the delusions could not happen in reality (aliens, television broadcasting your thoughts) then a person might be considered delusional with bizarre-type delusions.