New diagnoses added to the nomenclature reflect not so much the discovery of a previously unrecognized disease, pathogen, or lesion but are instead to efforts to fill gaps among existing categories. However, these new diagnostic categories can create additional boundary confusions.

Generalized social phobia

Schizoaffective disorder

Mixed anxiety-depressive disorder

These three diagnoses are examples because they are on the borders of domains of psychopathology that have been regarded as relatively distinct.