Comorbidity of borderline personality disorder and posttraumatic stress disorder in the U.S. population
Introduction
The overlap in phenomenological and conceptual aspects of borderline personality disorder (BPD) and posttraumatic stress disorder (PTSD) has been recognized since their initial inclusion in the third edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-III; Gunderson and Sabo, 1993, American Psychiatric Association, 1980). While placed on different axes of the DSM classification system, both disorders have important relationships with trauma. PTSD is an Axis I disorder characterized by persistent adverse reactions following exposure to a life-threatening traumatic event (American Psychiatric Association, 2000). Exposure to a traumatic event is not required for a diagnosis of BPD, but adverse experiences such as childhood physical and sexual abuse are commonly present in the life histories of individuals diagnosed with BPD, leading some authors to suggest that BPD be viewed as part of a posttraumatic stress “syndrome” (Zanarini et al., 1989, Goldman et al., 1992, Herman et al., 1989, Ogata et al., 1990). Further adding to the complexity in understanding the relationship between these disorders is the proposed construct of “complex PTSD,” which includes characterological alterations similar to those seen in BPD (Herman, 1992).
Existing studies of PTSD–BPD comorbidity have relied almost entirely on treatment-seeking clinical samples. These studies have suggested comorbid rates of PTSD among individuals with BPD ranging from 25% to 58% (Zanarini et al., 1998, Zlotnick et al., 2002, Zlotnick et al., 2003, Zimmerman and Mattia, 1999, Zanarini et al., 2004, Golier et al., 2003, Rusch et al., 2007, Famularo et al., 1991, Van Den Bosch et al., 2003, Yen et al., 2002, Harned et al., 2008, Linehan et al., 2006). Studies have reported similar rates of comorbid BPD among individuals with PTSD to range even more widely between 10% and 76% (Southwick et al., 1993, Heffernan and Cloitre, 2000, Shea et al., 1999, Zlotnick et al., 2002, Feeny et al., 2002; Clarke et al., 2008, Connor et al., 2002). Only two existing community studies have been able to assess PTSD–BPD comorbidity. One found that 10% of individuals with clinically significant PTSD symptoms also had BPD (Connor et al., 2002), while the second found that 34% of individuals with BPD had PTSD (Swartz et al., 1990). Although community samples, these studies were both conducted among adult respondents in North Carolina and to date, no findings generalizable to the US population exist.
The literature on psychiatric correlates of PTSD–BPD comorbidity is far from consistent. Some studies have found general psychopathology (Rusch et al., 2007) and depressive symptoms (Bolton et al., 2006) to be more prevalent among individuals with comorbid PTSD–BPD relative to individuals with BPD alone, while alcohol problems (Connor et al., 2002) and a greater number of Axis I diagnoses (Zlotnick et al., 2003) have been found to to be more prevalent among individuals with comorbid PTSD–BPD relative to those with PTSD alone. Some studies have found no differences in Axis I or II characteristics between those with comorbid PTSD–BPD and BPD alone (Zlotnick et al., 2003). Although not inconsistent findings, it is important to note that an increased likelihood of suicide attempts has been found among individuals with comorbid PTSD–BPD relative to those with PTSD alone (Connor et al., 2002, Heffernan and Cloitre, 2000). This difference has not been found when comparing individuals with PTSD–BPD to those with BPD alone (Rusch et al., 2007).
Examination of the relationship between childhood trauma and PTSD–BPD has resulted in somewhat more consistent findings. Most (but not all; Zlotnick et al., 2003) studies have found a relationship between sexual trauma and PTSD–BPD comorbidity compared to either BPD alone (Zlotnick et al., 2003, Van Den Bosch et al., 2003) or PTSD alone (Connor et al., 2002, Feeny et al., 2002). Some studies have additionally found comorbid PTSD–BPD to be associated with earlier abuse onset (Heffernan and Cloitre, 2000), physical abuse (Clarke et al., 2008), and verbal abuse (Heffernan and Cloitre, 2000) relative to individuals with PTSD alone. However, one study found individuals with comorbid PTSD–BPD to be associated with physical abuse and a greater number of types of abuse (Zlotnick et al., 2003) relative to individuals with BPD alone, but did not find these differences relative to those with PTSD alone.
The literature regarding extent of PTSD symptoms has also been conflicting, with some studies finding differences between the comorbid PTSD–BPD group and individuals with PTSD only (Zlotnick et al., 2002, Clarke et al., 2008) and others finding no such differences (Heffernan and Cloitre, 2000). In terms of BPD traits, one study found a higher mean number among those with comorbid PTSD–BPD relative to those with PTSD alone (Zlotnick et al., 2002), but studies have not found this difference relative to BPD alone (Zlotnick et al., 2002, Zlotnick et al., 2003).
Quality of life has also been infrequently studied, but one study demonstrated that individuals with comorbid PTSD–BPD have worse physical quality of life than those with BPD only (Bolton et al., 2006). Other studies have examined related measures, however, and have found individuals with comorbid PTSD–BPD to have a significantly lower global assessment of functioning and a higher likelihood of lifetime hospitalization compared to those with BPD alone and those with PTSD alone (Zlotnick et al., 2003). In addition, the one community study of this comorbidity found that individuals with PTSD–BPD were more likely to have fair to poor health and increased impairment in social and occupational domains relative to those with PTSD alone (Connor et al., 2002).
Inconsistent findings regarding correlates of PTSD–BPD comorbidity most likely stem from methodological differences across surveys. As mentioned, most studies have focused on treatment-seeking samples, which is likely to have biased findings toward increased severity of the index disorder(s). In addition, many studies were restricted to females (Rusch et al., 2007, Heffernan and Cloitre, 2000; Clarke et al., 2008, Feeny et al., 2002, Van Den Bosch et al., 2003) and many focused on further sub-samples such as individuals who have experienced sexual trauma (Clarke et al., 2008, Heffernan and Cloitre, 2000) or individuals with at least one personality disorder (Zlotnick et al., 2003). Additionally, some studies compare the comorbid group to either individuals with PTSD only or individuals with BPD only, limiting the comprehensiveness of the examinations (Heffernan and Cloitre, 2000, Bolton et al., 2006, Connor et al., 2002, Rusch et al., 2007, Clarke et al., 2008).
The only previous community survey to have addressed PTSD–BPD comorbidity was limited to a particular region of the U.S. and, moreover, had only a small number (n = 15) of respondents with both disorders (Connor et al., 2002). To date, no findings generalizable to the US population exist.
The current study is the first to examine the comorbidity of PTSD and BPD in a large, nationally representative sample using valid and reliable DSM-IV diagnoses. Not only does it provide the first general population estimate of the extent of PTSD–BPD comorbidity using DSM diagnoses, but it also explores a broad range of correlates of this comorbidity including presence of other psychiatric diagnoses, relationship to childhood traumatic events, age of onset of PTSD, extent of PTSD and BPD symptoms, and health-related quality of life. In addition, the current study provides the first opportunity for an examination of gender differences on the impact of this comorbidity. In order to comprehensively characterize the nature of PTSD–BPD comorbidity, three groups will be examined: respondents with PTSD only, respondents with BPD only and respondents with both PTSD and BPD. A better understanding of the discontinuity, overlap and consequences of overlap between PTSD and BPD holds great importance for clinicians.
Section snippets
Sample
The NESARC (Grant et al., 2003b, Grant and Kaplan, 2005) is a longitudinal nationally representative survey based on the civilian, non-institutionalized population of the 50 United States, age 18 and over. Data collection was supported by the National Institute on Alcohol Abuse and Alcoholism (NIAAA) and was conducted in two waves using face-to-face interviews. Wave I interviews (N = 43,093) were conducted between 2001 and 2002 by trained lay-interviewers who had an average of five years
Prevalence
The prevalence of lifetime PTSD (n = 2463) was 6.6% (SE = 0.18; 95% CI = 6.27–7.00) and the prevalence of BPD (n = 2231) was 5.9% (SE = 0.19; 95% CI = 5.51–6.28). Twenty four percent of individuals with lifetime PTSD also had BPD, while 30.2% of individuals with BPD also had PTSD. Ninety percent of the sample had neither PTSD nor BPD (n = 30,900, 95% CI = 89.9–90.2), 5.0% had PTSD without BPD (n = 1820, 95% CI = 4.7–5.3), 3.7% had BPD without PTSD (n = 1290, 95% CI = 3.4–4.0) and 1.6% had comorbid PTSD–BPD (n = 643, 95%
Discussion
This is the first study of PTSD–BPD comorbidity in a nationally representative sample using reliable and valid diagnoses of DSM-IV mental disorders. The principal finding is that individuals with comorbid PTSD–BPD carry a significantly greater burden of illness than individuals with either disorder alone. This was evident in terms of more symptoms, higher rates of comorbidity with other Axis I conditions, increased odds of suicide attempt(s), and poorer health-related quality of life.
Role of funding source
The NESARC was supported by the National Institute on Alcohol and Related Conditions (NIAAA) and the National Institute on Drug Abuse. The research was supported by a Social Sciences and Humanities Research Council (SSHRC) Canada Graduate Scholarship (Pagura), a Manitoba Health Research Council (MHRC) operating grant (Bolton), the Canada Research Chairs program (Cox), a Canadian Institutes of Health Research (CIHR) New Investigator Award (Sareen), the Swampy Cree Suicide Prevention Team CIHR
Contributors
Author Sareen provided the initial conceptualization of the project. All authors contributed to the planning of statistical analyses. Author Pagura conducted the statistical analyses and wrote the initial draft of the manuscript. All authors provided ideas and feedback to result in the final manuscript.
Conflict of interest
The authors have no conflicts of interest to report.
Acknowledgements
The NESARC was supported by the National Institute on Alcohol and Related Conditions (NIAAA) and the National Institute on Drug Abuse. The research was supported by a Social Sciences and Humanities Research Council (SSHRC) Canada Graduate Scholarship (Pagura), a Manitoba Health Research Council (MHRC) operating grant (Bolton), the Canada Research Chairs program (Cox), a Canadian Institutes of Health Research (CIHR) New Investigator Award (Sareen), the Swampy Cree Suicide Prevention Team CIHR
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