A diagnosis of “delusional disorder” is given when a person experiences one or more delusions within a period of 1 month or longer. Apart from the impact of the delusion(s), functioning is not markedly impaired, and behavior is not obviously bizarre or odd. If manic or major depressive episodes have occurred, they have been brief compared to the duration of the delusional periods. The diagnosis requires that major schizophrenic features are not present, and the delusion(s) is not attributable to the physiological effects of a substance, another medical condition, or other mental disorder such as body dysmorphic disorder or obsessive-compulsive disorder.

Types of delusional disorders include:

• Erotamanic type – when the delusion is that another person is in love with the individual.
• Grandiose type – when the delusion is having some great (but unrecognized) talent or insight, or having made some important discovery.
• Jealous type – when the delusion is that the individual’s spouse or lover is unfaithful.
• Persecutory type – when the delusion involves the belief that the individual is being conspired against, cheated, spied on, followed, poisoned or drugged, harassed, or obstructed in the pursuit of long-term goals.
• Somatic type – when the individual believes that he or she has a physical defect or medical problem when none exists.
• Mixed type – when no one delusional theme predominates.
• Unspecified type – applies when the dominant delusional belief cannot be clearly determined.