Depression and borderline personality disorder.

Borderline personality disorder (BPD) is a serious mental illness characterised by dysregulation of emotions and impulses, an unstable sense of self, and difficulties in interpersonal relationships, often accompanied by suicidal and self-harming behaviour. Major depressive disorder (MDD) commonly co-occurs with BPD. Patients with BPD often present with depressive symptoms. It can be difficult to distinguish between BPD and MDD, especially when the two disorders co-occur. Research is needed to clarify the commonalities and differences between BPD and MDD, and BPD and rapid-cycling bipolar disorder. When MDD and BPD co-occur, both conditions should be treated concurrently. MDD co-occurring with BPD does not respond as well to antidepressant medication as MDD in the absence of BPD. MDD is not a significant predictor of outcome for BPD, but BPD is a significant predictor of outcome for MDD. Treatment of BPD with specific psychotherapies tends to result in remission of co-occurring MDD. Empirically validated psychotherapies for BPD share common features that are applicable in all treatment settings where patients with BPD are likely to present, including primary care. Methodologically sound research is required to examine the effectiveness of medications for treatment of MDD co-occurring with BPD.