Comorbidity of bipolar disorder and borderline personality disorder: Phenomenology, course, and treatment considerations

Abstract Aim Bipolar disorder (BD) and borderline personality disorder (BPD) are both serious psychiatric conditions that elevate the risk for harmful outcomes. Although these conditions represent distinct diagnostic entities, existing research suggests that approximately 20% of individuals with BD meet the criteria for comorbid BPD. Individuals with comorbid BD/BPD appear to have a markedly more severe and phenomenologically distinct clinical course when compared with those with BD alone. However, treatments have generally not been tested in this specific population, and currently, no formal treatment guidelines exist for this subgroup of patients. Method In the current paper, we review the epidemiological and descriptive research characterizing those with comorbid BD/BPD and discuss the impact of this comorbidity on psychosocial treatment. We also review current findings on evidence‐based treatments for BD and BPD that show promise in treating those with comorbid BD/BPD. Results In our review of the literature, we highlight the importance of recognizing this comorbidity and discuss avenues for developing and integrating evidence‐based treatment approaches for this understudied clinical population. Conclusions Although formal trials of interventions targeted to comorbid BD/BPD are limited, there is promising evidence regarding the possibility of using or integrating existing evidence‐based approaches for this population. There are also several areas of clinical practice improvement and future research directions that stem from this literature.