THE term "borderline" is used with increasing frequency for psychiatric patients who do not fit any of the categories listed in the Diagnostic and Statistical Manual of Mental Disorders or other classificatory publications.1 The looseness of the term reflects the difficulties inherent in classifying under a single heading a gamut of symptoms ranging from those found in one or another type of schizophrenia to some form of character disturbance. On the other hand, the persistence of this not officially recognized diagnostic label indicates a shift from symptom-oriented to patient-centered psychiatric thinking. It underlines the fact that fewer patients present discrete, well-defined disorders, and that more and more patients (and their environment) appear to suffer from pervasive, multilevel disturbances which are not clearly compatible with either a neurotic or a psychotic personality organization (compare Kernberg2 and Knight3).
The parameters of borderline have been no more clearly defined
Doris Gruenewald. A Psychologist's View of the Borderline Syndrome. Arch Gen Psychiatry. 1970;23(2):180–184. doi:10.1001/archpsyc.1970.01750020084011