This disorder is characterized by the presence of one or more false beliefs that persist for at least a month. There are persistent, persecutory, nonbizarre delusions about situations that may occur in real life, such as being followed, poisoned, or subjected to jealousy, with emotions and behaviors appropriate to the content of the delusional system. The delusions may be deemed bizarre, if they are clearly unbelievable, not understandable, and not derived from ordinary life experiences. This disorder was formerly referred to as paranoid disorder.

The disorder is relatively rare, and its cause is unclear. It may or may not be common among relatives of individuals with schizophrenia. The delusion may be due to the physiological effect of a substance or a general medical condition.

The characteristics of delusional disorder may include: feelings of being exploited; reading threatening meanings into innocent comments or events; persistent bearing of grudges; responding to perceived slights; pervasive distrust; and suspiciousness of others. The signs and symptoms presented by the person will also depend on the subtype of the delusional disorder. The subtypes of delusional disorder based on the central delusional theme are as follows:

• The ergomanic type is characterized by the person's belief that someone, usually in a high position, is in love with the person.

• The grandiose type is characterized by the person's mistaken belief of inflated worth, power knowledge and identity, or a special relationship with a famous person.

• The unspecified type is characterized by persons for whom the dominant delusion cannot be clearly determined, or is described in one of the other types.

A comprehensive clinical assessment is conducted by obtaining a through history, and ruling out other specific conditions associated with delusions. Assessing how dangerous the patient might be by determining the extent to which the patient is willing to act on his delusion is significant. Specific diagnostic criteria for the condition include:

• Delusions involving situations that could occur in real life, e.g., being followed, infected, deceived, etc., for at least one month.

• Criterion A for schizophrenia (Diagnostic Code: 9204 Schizophrenia) has not been met.

• Separate from the delusions, functioning is not greatly impaired and behavior is not significantly bizarre.

• Delusional periods are considerably longer than concurrent mood episodes with delusions.

• The disturbance cannot be attributed to a substance, medication, or general medical condition.

Treatment of the condition involves effective physician-patient relationship, drug therapy, and management of complications. Hospitalization is necessary if the patient is considered to be dangerous.

The delusion may progress gradually, or it may never reoccur. The condition does not generally lead to severe impairment or change in personality.