Co-morbidity of bipolar disorder and borderline personality disorder: findings from the National Epidemiologic Survey on Alcohol and Related Conditions.

OBJECTIVES Clinical studies suggest a high co-morbidity rate of borderline personality disorder (BPD) with bipolar disorder (BD). This study examines the prevalence and correlates of BPD in BD (I and II) in a longitudinal population-based survey. METHODS Data came from waves 1 and 2 (wave 2: N=34,653, 70.2% cumulative response rate; age ≥ 20 years) of the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC). Lay interviewers conducted in person interviews using the Alcohol Use Disorders and Associated Disabilities Interview (AUDADIS-IV), a reliable diagnostic tool of psychiatric disorders based on DSM-IV criteria. Subjects with BD I (n=812), BD I/BPD (n=360), BD II (n=327) and BD II/BPD (n=101) were examined in terms of sociodemographics, mood, anxiety, substance use and personality disorder co-morbidities and history of childhood traumatic experiences. RESULTS Lifetime prevalence of BPD was 29.0% in BD I and 24.0% in BD II. Significant differences were observed between co-morbid BD I/II and BPD versus BD I/II without BPD in terms of number of depressive episodes and age of onset, co-morbidity, and childhood trauma. BPD was strongly and positively associated with incident BD I (AOR=16.9; 95% CI: 13.88-20.55) and BD II (AOR=9.5; 95% CI: 6.44-13.97). CONCLUSIONS BD with BPD has a more severe presentation of illness than BD alone. The results suggest that BPD is highly predictive of a future diagnosis of BD. Childhood traumatic experiences may have a role in understanding this relationship.