Borderline personality disorder and violence in the UK population: categorical and dimensional trait assessment

Design and sample

The sample was drawn from the first phase of the ONS Survey of Psychiatric Morbidity among Adults in Great Britain (2000) and the Adult Psychiatry Morbidity Survey (2007), two British national surveys of adults aged 16 years and older living in households in England, Scotland and Wales in 2000, and in England in 2007. A total of 8580 adults completed a first-phase interview (response rate 69.5 %) in the 2000 survey and 7393 in 2007 (response rate 57.0 %). Design and sampling procedures have been previously described [20, 21]. Of the total sample, 1220 (7.6 %) were excluded due to missing data on the exposure (BPD) and on the violent behaviours module. Because each survey employed the same measures of PD, demography, clinical covariates and violence outcomes, we conducted joint analyses of individual-level data for a total weighted sample of 14,753.

Measures

Individual BPD criteria and violence

In contrast, anger was significantly associated with all violent outcomes except towards family members. Impulsivity was associated with violence repetition, victim injury and minor incidents, towards intimate partners, family members and other known persons, in their own homes, as well as outdoors and in bars/pubs. There were associations between avoid abandonment and violence towards intimate partners, known persons, and in all locations except the participants’ home.

Individual BPD criteria by gender

Stratified analyses of BPD criteria by gender revealed further differences. For males, paranoid ideation was associated with all key violent outcomes: violence when intoxicated (OR 2.07 CI 95 % [1.38, 3.10], p <0.001), repetitive violence (OR 2.91 CI 95 % [1.69, 5.01], p <0.001), violence leading to injuries (OR 2.19 CI 95 % [1.37, 3.50], p <0.001) and minor incidents of violence(OR 1.70 CI 95 % [1.05, 2.76], p<0.05). However, among women it was not associated with any of these outcomes. In women, unstable relationships was associated with violence (OR 1.44 CI 95 % [1.04, 2.01], p <0.05), but mostly of minor consequence (OR 1.81 CI 95 % [1.16, 2.83], p <0.01) and towards intimate partners (OR 1.59 CI 95 % [1.03, 2.45], p <0.05). There were no associations among males for this criterion.

For both men and women, the impulsivity criterion was similarly associated with most violent outcomes.

Dimensional BPD traits and violence: differences by gender

The adjusted linear association of the dimensional (severity) trait scale was significant (OR 1.42 CI 95 % [1.31, 1.54], p <0.001). A gender X BPD dimensional traits interaction term in this model was significant (OR 0.86 CI 95 % [0.75, 0.98],p <0.05), indicating that the linear increase between BPD traits and violence is significantly higher in women (OR 1.56 CI 95 % [1.41, 1.72], p <0.001) compared with men (OR 1.34 CI 95 % [1.20, 1.49], p <0.001).

Individual BPD symptoms and violence

BPD is a complex disorder which is frequently correlated with other risk factors for violence [35]. In the present study, it was highly comorbid with all other categories of mental and emotional distress, including anxiety and psychotic symptoms. Analyses were therefore performed at the individual criteria level. These revealed differential correlates between violence and individual BPD criteria. As expected, Anger and impulsivity were associated with higher risk for most violent outcomes. Anger was more than twice as likely to be associated with repetitive violence and with violence directed at intimate partners. A caveat is required as one of the questions that assesses the BPD SCID-II anger criterion is “Do you hit people or throw things when you get angry?”, indirectly measuring aggressiveness.

Avoid abandonment was also directly linked to the outcomes, with violence limited towards intimate partners or persons known, and in which the perpetrator was injured. This would suggest violent altercations had resulted from perceived rejection and acting under threat of being abandoned. Taken together with the disproportionately high rates of comorbidity with anxiety, it is likely that these individuals may have experienced insecure-anxious attachments in early life which had continued into adulthood in their close relationships [36]. Insecure-anxious attachments refer to the perceived availability of attachment figures, thought to develop through inconsistent patterns of early care. Under high levels of stress, they frequently amplify the severity of their adversities, become obsessed with thoughts of being abandoned by partners, with accompanying intense negative emotions [37, 38].

Our analyses showed that several BPD traits are independently linked with violence. BPD is a very heterogeneous disorder and includes symptoms across cognitive, affective, interpersonal and impulse control domains [39]. That different BPD traits were associated with violence, such as anger, impulsivity, and avoid abandonment is consistent with the assertion that violence related to PD is driven conceptually by a combination of high expressions of internalising and externalising traits, especially in the context of co-occurring ASPD [35]. Comorbidity between ASPD and BPD is high [40], and this perspective especially accounts for the wide heterogeneity of violence perpetration, taking place in various contexts (for in depth review, see Howard, 2015 [35]). Moreover, the different correlates of violence from BPD traits appear to operate differentially by the externalising and internalising aspects of BPD pathology, and in turn, the internalising pathway appears more prominently represented in women.

Suicidal behavior, affective instability and emptiness were not independently associated with any violent outcomes. These traits represent the depressive-mood dimension of BPD. Previous research has shown that depressive disorders are associated with reduction of violence both in clinical samples [41, 42] and at the population level [43]. In the present study, these BPD traits were not protective. However, they may have cancelled out or attenuated the effects of other criteria when using the categorical classification for analysis. Although suicidal behaviour is an aggressive act towards the self and may occur in the context of impulsivity, it was not associated with interpersonal violence in this study. Self-directed violence is consistent with a model of depression in which aggression is turned inwards [44]. Our findings may therefore indicate contrasting emotional and behavioural dynamics for outwardly expressed violence. Finally, the identity disturbance criterion was inversely associated with violence, indicating a protective effect.

Differences by gender

Our data shows that BPD traits were differentially associated with violence for men and women. Stratification shows that women who endorsed unstable relationships were significantly more prone to engage in minor violence, directed at their partners. However, there were no associations with violence among men and unstable relationships. Certain traits were associated with violence for both men and women, including anger, impulsivity, and to a lesser extent avoid abandonment. However, male violence was strongly associated with paranoid ideation when under stress. This suggests a potential mechanism for interpersonal violence perpetuated by men, characterised by general suspiciousness and jealousy within intimate relationships. The link between this borderline personality trait and violence resembles the ‘BD’ subtype described by Holtzworth-Munroe et al. [34] in their typology of male batterers where violent men are thought to have deficits in their marriage and relationships skills, embrace hostile attitudes towards women, and are characterised by extreme jealousy. It is hypothesised that these men may have experienced early trauma and abuse, with a destructive effect on their personality organization, which leads to intimate partner violence. For example, men endorsing the paranoid ideation trait were almost four times as likely to be violent towards intimate partners in our study, lending support to this typology. This is also consistent with recent findings indicating that the pathway from early abuse to IPV is mediated by personality disorder amongst young men [45]. However, an alternative explanation is that this personality trait overlaps with the suspiciousness criterion of other cluster B personality disorders.

We found that change in the linear increase of BPD symptoms on violence is higher among women in contrast to men. This indicates that women are more susceptible to becoming violent with increasing BPD traits, as this increase reduces the base rate gender differences in violence in our sample. This symptom by gender interaction shows that women are more prone to engage in violence due to abnormal personality traits, specifically BPD. Conversely, for men, BPD traits showed a more linear (stable) association, with a higher base rate for violence.

Limitations

The population sample used in this study is to our understanding the largest used for evaluating the association of BPD and violence, which ensures generalizability. This allowed us to test complex models while minimizing estimate bias. However, the present findings should to be considered in the context of several limitations. Firstly, diagnostic categories in this survey were derived from the structured SCID-II screening questionnaire, which was administered by lay interviewers without clinical training. It is likely that the SCID-II screen resulted in a number of false positives, a problem with self-report questionnaires when making PD diagnoses [46]. Despite this limitation, our reported BPD prevalence of 1.5 % is remarkably similar to the 1.4 % reported in the National Comorbidity Survey Replication [47], and slightly lower than the revised NESARC prevalence [48].

Another important limitation was that the associations between PD and violence may include content overlap (shared variance). Violent behaviour forms part of the criteria for conduct disorder (initiating physical fights, using a weapon) and also among items occurring after the age of 15 (irritability), which may coexist with BPD criteria. The use of self-reported violence was another limitation. Although self-report is commonly used to investigate general and partner violence, evidence suggests that subjects tend to under-report aggression [49], although reliance on official statistics including criminal records would result in substantially greater underreporting of all forms of violence except the most serious. Finally, the cross-sectional nature of the design limits any conclusions regarding causality between BPD traits and BPD as a categorical construct in its association with violence.

Nevertheless, the present study further demonstrates the value of assessing underlying traits directly, thereby lending support to emerging models that focus on basic personality features discussed in the literature [17, 24].

Implications

Our finding that a clinical diagnosis of BPD was not independently associated with violence outside of intimate partner relationships has important implications for treatment and management. BPD is associated with stigma and patients have been excluded from services in the past. Correspondingly, BPD has not been found to be independently associated with violent or sexual convictions among prisoners [50]. Nevertheless, BPD is highly prevalent among correctional populations and we found that it is associated with violence when comorbid with other psychiatric conditions in the general population. This indicates firstly, the need for further research into the mechanisms of how BPD interacts with comorbid psychopathology, together with the possibility that it has synergistic effects with certain conditions. Secondly, that BPD mediates between certain risk factors and violence. For instance, BPD traits have been shown to mediate between childhood maltreatment and IPV [51]. Thirdly, BPD and certain risk factors for violence may have a common aetiology.

Our findings of a strong and independent relationship between BPD and IPV must be placed in the context of our previous findings from this combined UK community sample. Self-reported violence towards partners was more prevalent among women than men. However, the risks of becoming physically injured in a violent altercation with a partner were considerably higher among women than men [52]. A small but important community study has emphasised the importance of using dyadic couples in studying the associations between BPD traits and IPV, and has confirmed previous research showing that each partners’ personality traits can influence the other’s [53]. More BPD traits among men were associated with more violence towards partners and victimisation by their partners, whereas women’s BPD traits were associated only with their victimisation [54]. Our findings are therefore important in demonstrating that BPD traits among women in this larger community sample were also associated with violence directed at their partners, but that there are also differential associations between BPD traits and violence between men and women. These differences must also be placed in the context of additional findings from our sample: very few men were exclusively violent towards their partners [52]. Violence within relationships is commonly bidirectional and these findings demonstrate why violence directed against women by men carries higher risks and is more persistent, together with why strategies to treat men have been less successful. BPD traits among violent men are therefore important in contexts outside of their relationships and can include violence towards strangers. A narrow approach towards violence within relationships is therefore unlikely to be effective when treating men.

Our findings have additional importance both for treatment of women with BPD and women who are violent towards partners. More information is needed on the prevalence of violence in clinical samples of BPD and this may be a relatively unrecognised problem compared to self-harming behaviour. Clinicians should therefore ask about violence towards others among both male and female patients with BPD. However, assertions that women’s violence towards partners is more likely to be motivated by self-defence and fear whereas men’s is more likely to be associated with control motives [55] may be simplistic and unhelpful in the assessment of IPV, particularly in the treatment of women with BPD and violent women with BPD traits. More complex factors of fear of abandonment and associated states of severe anxiety, which in turn are associated with early disordered attachments that have persisted into adulthood, indicate specific goals for treatment, together with the need for support for partners to maintain supportive relationships.