Determining if Borderline Personality Disorder and Bipolar Disorder Are Alternative Expressions of the Same Disorder: Results From the National Epidemiologic Survey on Alcohol and Related Conditions

Objective: To examine whether bipolar disorder and borderline personality disorder represent 2 different disorders or alternative manifestations of the same disorder.

Methods: The data were collected between January 1, 2004, and December 31, 2005. The analyses were conducted between December 21 and December 27, 2010. Exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) were performed on 25 symptoms assessing depression, mania, and borderline personality disorder from the National Epidemiologic Survey on Alcohol and Related Conditions, a large nationally representative sample of the US adult population (N = 34,653). DSM-IV criteria were used for diagnosis of bipolar disorder and borderline personality disorder.

Results: A 3-factor solution provided an excellent fit in both the EFA (root mean square error of approximation [RMSEA] = 0.017, comparative fix index [CFI] = 0.997) and the CFA (RMSEA = 0.024, CFI = 0.993). Factor 1 (Borderline Personality Disorder) loaded on all 9 borderline personality disorder symptoms, factor 2 (Depression) loaded on 8 symptoms of depression, and factor 3 (Mania) loaded on 7 symptoms of mania plus the psychomotor agitation item of the depression section. The correlations between the Borderline Personality Disorder and Depression factors (r = 0.328) and between the Borderline Personality Disorder and Mania factors (r = 0.394) were lower than the correlation between Depression and Mania factors (r = 0.538).

Conclusions: A model with 3 positively correlated factors provided an excellent fit for the latent structure of borderline personality disorder and bipolar disorder symptoms. The pattern of pairwise correlations between the 3 factors is consistent with the clinical presentation of 2 syndromes (depression and mania) that can be characterized as a unitary psychiatric entity (bipolar disorder) and a third syndrome (borderline personality disorder) that is often comorbid with bipolar disorder. The findings converge in suggesting that bipolar disorder and borderline personality disorder are overlapping but different pathologies. These findings may serve to inform ongoing efforts to refine the existing psychiatric nosology and to suggest new avenues for etiologic and treatment research.