A comparison of depressed patients with and without borderline personality disorder: implications for interpreting studies of the validity of the bipolar spectrum

The nosological status of borderline personality disorder as it relates to the bipolar disorder spectrum has been controversial. Studies have supported, in part, the validity of the bipolar spectrum by demonstrating that these patients, compared to patients with nonbipolar depression, are characterized by earlier age of onset of depression, recurrent depressive episodes, comorbid anxiety and substance use disorders and increased suicidality. However, all of these factors have likewise been found to distinguish depressed patients with and without borderline personality disorder. A family history of bipolar disorder is one of the few disorder specific validators. In the present study from the Rhode Island Methods to Improve Diagnostic Assessment and Services (MIDAS) project, we compared the demographic and clinical characteristics of depressed patients with and without borderline personality disorder. We hypothesized that many of the factors used to validate the bipolar spectrum will also distinguish depressed patients with and without borderline personality disorder except, however, a family history of bipolar disorder. Two thousand nine hundred psychiatric outpatients at Rhode Island Hospital were evaluated with the Structured Clinical Interview for DSM-IV (SCID) and Structured Interview for DSM-IV Personality Disorders (SIDP-IV). Family history information regarding first-degree relatives was obtained from the patient using the Family History Research Diagnostic Criteria. One hundred and one patients with borderline personality disorder plus major depressive disorder were compared to 947 patients with major depressive disorder alone on the prevalence of bipolar disorder validators. Compared to depressed patients without borderline personality disorder, depressed patients with borderline personality disorder had a younger age of onset, more depressive episodes, a greater likelihood of experiencing atypical symptoms and had a higher prevalence of comorbid anxiety disorders, substance use disorders, and number of previous suicide attempts. The depressed patients with borderline personality disorder did not significantly differ from the patients without borderline personality disorder on morbid risk for bipolar disorder in first degree relatives. In addition, patients with a diagnosis of bipolar disorder had a significantly higher morbid risk of bipolar disorder in first degree relatives than the borderline personality disorder group. The findings indicate that many factors used to validate the bipolar spectrum are not disorder specific. These results raise questions about studies of the validity of the broad bipolar spectrum that do not assess borderline personality disorder. Our results do not support inclusion of borderline personality disorder as part of the bipolar spectrum.