Descriptive and longitudinal observations on the relationship of borderline personality disorder and bipolar disorder

Objective: The purpose of this study was to test whether borderline personality disorder is a variant of bipolar disorder by examining the rates of co- occurrence in both disorders, the effects of co- occurrence on a longitudinal course, and whether the presence of either disorder confers the risk for new onsets of the other. Method: A prospective repeated- measures design with reliable independent diagnostic measures and 4 years of followup was used to assess 196 patients with borderline personality disorder and 433 patients with other personality disorders. Results: Patients with borderline personality disorder had a significantly higher co- occurrence of bipolar disorder ( 19.4%) than did patients with other personality disorders. However, this co- occurrence did not appear to affect the subsequent course of borderline personality disorder. Although only 8.2% of the borderline personality disorder patients developed new onsets of bipolar disorder, this rate was higher than in patients with other personality disorders. Patients with other personality disorders with co- occurring bipolar disorder generally had more new onsets of borderline personality disorder ( 25%) than did patients with other personality disorders without co- occurring bipolar disorder ( 10%). Conclusions: A modest association between borderline personality disorder and bipolar disorder is reported.