The influence of borderline personality traits on clinical outcomes in bipolar disorder

Objectives: Systematic reviews suggest comorbid borderline personality disorder is presentin approximately 20% of individuals who have bipolar disorder, but current diagnosticsystems demonstrate a move towards dimensional rather than categorical approaches toclassifying personality pathology. We aimed to examine the presence and severity ofborderline personality traits in bipolar I and bipolar II disorder, and to explore associationsbetween the presence/severity of borderline personality traits and clinical outcomes inbipolar disorder. Methods: Borderline personality traits were measured in 1447 individuals with DSM-IVbipolar disorder (1008 bipolar I disorder and 439 bipolar II disorder) using the BorderlineEvaluation of Severity over Time (BEST) questionnaire. Lifetime clinical outcomes wereassessed via Schedules for Clinical Assessment in Neuropsychiatry (SCAN) semi-structuredinterview and clinical case-notes. Results: Borderline personality traits were common in both bipolar disorder groups, with86.2% participants reporting at least one trait. These included traits that overlap with (forexample, mood instability) and those that are distinct from the symptoms of bipolardisorder (for example, fear of abandonment). Borderline personality traits weresignificantly more frequent and more severe in bipolar II disorder compared to bipolar Idisorder. More severe borderline traits, and even the presence of a single borderlinepersonality trait, were significantly associated with younger age of bipolar disorder onsetand higher prevalence of lifetime alcohol misuse in both bipolar disorder groups. Conclusions: The presence of comorbid borderline personality traits should be considered inthe management of all patients with bipolar disorder irrespective of whether criteria for acategorical borderline personality disorder diagnosis are met