Beliefs that are in stark contrast to reality, often having to do with persecution or an exaggerated sense of importance or glory.

Delusions are generally experienced by people suffering from a severe psychotic disorder, usually schizophrenia, although delusional thinking can occur in other types of patients (as the result of drug or alcohol abuse, for instance). Typical delusional ideas are categorized into delusions of grandeur, in which a person imagines for him or herself some God-given purpose or, in some cases, believe they are in fact historical personalities of great importance. Another type of delusion are delusions of persecution, in which a patient will believe that some person or group is out to harm him. Still another set of delusions involve what are referred to as "command hallucinations," in which a person...