Delusional disorders: boundaries of a concept.

In 1987, DSM-III introduced the term delusional disorder. In so doing they gave new life to a concept that had predated but was delineated in its modern form by Kraepelin and developed most notably in France in the second and third decades of this century. While the current concept of delusional disorder is defined in a manner that distinguishes it from schizophrenia, a consideration of the evolution of thinking about delusional syndromes in France suggests that current distinctions are based on descriptive convenience rather than any understanding of the mechanisms that might produce phenotypic variations. If the purpose of accurate descriptions is to assist research, this state of affairs would seem unsatisfactory.