The state of knowledge in the area of suggested biological markers that may delineate subpopulations of patients with borderline personality disorders (BPD) is reviewed. There is widespread disagreement as to the specificity of these markers. The clinical implications of Axis I — Axis II, state vs. trait, acute vs. chronic, and definite vs. probable diagnoses, all seem to contribute to the confusion in this area. Some patients with BPD and with schizotypal personality disorders (SPD) share neuroendocrine abnormalities with affective disorders (AD) and schizophrenic (SCH)patients respectively. This interface and/or potential overlap between personality disorders (PD) and the major mental disorders is discussed with special reference to the DST, TRH/TSH test, and REM latency which have already been established as valuable biological markers for certain subtypes of depression. In contrast, biologic abnormalities observed in chronic schizophrenia are also present in some SPD patients. Current data are supportive of the hypothesis that some PD patients are independent whereas others are genetically related to the major mental disorders.
