The classification of delusional disorders

Recognition of a delusion in a psychiatric illness places that illness in the broad category of psychotic disorders. The form and content of the delusion are, in themselves, however, insufficient to make a detailed diagnosis, and it is the context of the delusion within a particular disorder that is more pathognomonic. Among the large number of illnesses whose symptoms include delusions, there is a discrete group known as the delusional disorders. After many years of neglect, these are becoming of considerable interest to psychiatrists, and research to define their characteristics is on the rise. This article attempts to describe these illnesses, to indicate where possible their relationships to other psychiatric disorders, and to suggest promising areas of investigation.