Discriminative Validity of the Borderline Syndrome Index

Borderline Syndrome Index (BSI) scores were not significantly different between the following DSM-III-R principal diagnoses: borderline personality disorder (BPD, n = 24), major affective disorder (AD, n = 24), dysthymia (n = 7), and schizophrenia (n = 23). However, there was diagnostic overlap between BPD and the mood disorders, and this influenced scores. A concomitant diagnosis of dysthymia or AD in patients with BPD led to significant increases in BSI scores compared to patients with BPD or AD only, whereas BPD patients meeting criteria for both dysthymia and AD had significantly higher BSI scores compared to those patients with a single diagnosis of BPD, AD, or dysthymia. BSI scores for the subgroup of AD with dysthymia were significantly higher than scores for individuals with only AD or BPD. The findings suggest that the BSI is not able to distinguish borderline personality disorder as a single diagnostic entity from other diagnoses, although it may offer a measure of generalized deficiency in coping with life associated with chronicity of illness.