RESUMEN
Symptoms of borderline personality disorder (BPD) and bipolar disorder (BD) often overlap. In some cases, it is difficult to conduct a differential diagnosis based only on current diagnostic criteria Therefore, it is important to find clinical factors with high discriminatory specificity that, used together with structured or semi-structured interviews, could help improve diagnostic practice. We propose that a clinical analysis of identity, self-concept and self-esteem may help distinguish the two disorders, when they are not co-morbid. Our review of the studies that analyse these constructs in BD and BPD, separately, points in the direction of qualitative differences between the two disorders. In BPD, there is a well-documented identity diffusion, and the self-concept appears predominantly negative; shifts in self-concept and self-esteem are often tied to interpersonal triggers. In BD, patients struggle with their identity, but narrative identity might be less compromised compared with BPD; the shifts in self-concept and self-esteem appear more linked to internal (i.e. mood and motivational) factors. We end the paper by discussing the implications for clinicians and ideas for future comparative research.