A systematic review on the relationship between antisocial, borderline and narcissistic personality disorder diagnostic traits and risk of violence to others in a clinical and forensic sample
The review highlights the complexity of the relationship between violence and a PD diagnosis, as well as the limitations of the current literature with regards to the functional link. Current research does infer a relationship, albeit it weak and gender biased. Research also shows that the aetiology of violent behaviour attributed to PD is low in comparison to other well-known risk factors such as substance abuse and lifetime severe mental illness [45] Table 2. Summarises the key findings related to the specific PD diagnostic traits.
Summary of evidence
Most of the studies reviewed, failed to empirically research the individual Cluster B personality traits, and instead chose to consider diagnosis as a sole entity. As there can be many combinations of traits in order to meet the clinical cut-off for a diagnosis of each of the Cluster B PDs, there is a need to look in-depth at those traits that distinguish individuals with a who engage in violent behaviours from those who do not.
This literature search highlighted the lack of empirical studies investigating the link between pathological NPD traits and violent behaviour, despite it being anecdotally linked to violence risk management for some time. Warren and South [49] highlighted the significance of considering narcissistic traits in violence risk assessment, when there is a tendency for professionals to link violence solely with ASPD.
Key findings from the literature in relation to NPD traits indicate that delusions of a grandiose nature, when associated with elation or anger can present a direct pathway to serious violence [44]. This lends consideration to precipitating factors that can influence elation or anger, such as substance misuse for example, which is known to be associated with PD, violence, and aggression [37]. Emotion dysregulation could also precipitate elation or anger, which may account for violence perpetration in the context of an inflated sense of entitlement being or feeling violated, as identified by Fisher and Hall [18]. From a Schema-focussed perspective, a violated sense of entitlement could result in behavioural externalisation of aggression as a means to overcompensate for such feelings of entitlement [28]. Further insight could be taken from the tenuous relationship identified between impaired accuracy in perspective taking and traits impulsivity and recklessness [41]. Impaired perspective taking was also identified to exacerbate anger arousal [9], which may thus enhance risk of impulsive and/or reckless violence.
Trait “aggressiveness” was identified to relate to NPD, however this was distinguished to refer solely to the emotional trait of aggressiveness, being anger and irritability, as opposed to physical acts of aggression [19]. Despite this, NPD comorbid with other PDs, significantly enhances the risk of serious physical violence, particularly murder [49], which supports the inference that trait impulsivity, associated with ASPD and BPD, may present a significant elevating risk factor towards the perpetration of physical violence or aggression in the context of NPD traits. The trait of impulsivity has theoretical linkage to personality structure as well as aggressive or violent behaviour [29]. In fact, Elonheimo et al. [15] discussed how they felt “violence may be attributed more to impulsiveness than actual mental disorder; it may arise out of situational factors, provocation, and an emotional surge”.
Research into violence associated with BPD was found to centre on domestic violence perpetration. In formulating violence associated with BPD traits, Goldenson et al. [22], identified that personal histories of trauma, commonly associated with dimensions of PDs [23], relate to less secure attachment styles, indicative of trait “avoid abandonment”. Of which, both avoidant and anxious attachment in the context of BPD or ASPD diagnoses relate to intimate partner violence [34] and avoidant attachment was predictive of the severity of intimate partner violence [31]. Emotion dysregulation was identified to be a superior predictor of assault perpetration, physical and psychological aggression, than trait impulsivity [40], indicating that trait “affective instability” is an important contributory factor to interpersonal difficulties and resultant violence or aggression. The influence of affective instability on violence is further supported by Shorey et al. [42], as despite impulsivity being a predictor of aggression and trait anger, the finding that affective trait anger mediates the relationship between impulsivity and physical aggression, along with the finding that higher levels of psychological distress, psychopathologised as depression and paranoid ideation, related to more physically aggressive behaviour [7] suggest the affective accountability and relevance to violence perpetration. Nevertheless, trait impulsivity, though likely precipitated by affective instability, remains to present a risk factor as it has been deemed to account for acts of physical aggression in the context of BPD by Fossati et al. [19].
ASPD symptoms were reported to directly predict greater physical assault perpetration and victimization and were not associated with difficulties regulating emotions [40]. Hostile attributions and trait impulsivity have been shown to correlate with a history of persistent violence in the context of ASPD [27] and Crick and Dodge [6] have proposed a model that emphasizes that violence occurs as a result of a chain of events propelled initially by making hostile attributions.
The literature identifies a clear overlap between traits and/or symptoms across PD diagnoses and offers some insight into the relevance of trait presence, comorbidity and interaction in the formulation and prediction risk of violence. It is therefore important to be mindful of a number of difficulties when it comes to the relationship between risk of violence and offenders with PDs, in order not to attribute unrealistic weighting to PDs in risk management. Firstly, it is likely that violence is overestimated as a risk in PDs as a whole, due to confounding variables such as sociodemographic factors and co-morbidity with other Axis II disorders, Axis I disorders and substance abuse [1]. In fact, Tyrer et al. [43] refers to the “morass of comorbidity” as holding the key to the causal relationship between PD and violence.
It is perhaps in scrutinising this concept of comorbidity, that insight can be elicited in regard to the complex interactions between specified traits that may point towards a more idiographic approach to risk management. Though the research is not presently at a point to be comprehensive, certain patterns are emerging in relation to the presence and dynamic interaction of diagnostic traits which point towards a preliminary model that may be more relevant to clinicians in assessing and managing violence with individual PD diagnoses. The presence of such diagnostic traits for individuals does not always nor consistently result in violent behaviour, which further complicates their accountability for risk attribution in assessment. It is proposed then, that in formulating risk, the presence of such traits may serve as predisposing factors which, when precipitated by their idiosyncratic interaction, emotional arousal or dysregulation, interpersonal difficulties and or impulsivity, which were common features in the literature, risk of presenting violence may be predicted.
As a preliminary attempt to illustrate this, Fig. 2, places violence, as previously defined via the HCR-20, at the centre of the model as the presenting problem. The next layer depicts the three main contributory factors that the literature indicates may precipitate violence (emotion dysregulation/arousal, interpersonal difficulties and impulsivity); all of which are proposed to influence one another non-directionally with an aggregate effect. The degree to which these factors interact (and thus result in violence) however, depends on the precipitating traits that are present, or that have been triggered, and their interaction with one another. It is therefore the interplay of the predisposing traits which influence the degree to which precipitating factors aggregate to present in violent behaviour.
Violence formulation model
In explaining the inconsistency in presenting violent behaviour, the presence of predisposing PD traits may exist and interact with precipitating factors in a dysfunctional yet non-violent manner, but may escalate in risk on interacting or being augmented by further traits. For example, an individual with the predisposing trait “unstable relationships” may experience chronic interpersonal difficulties that may have the potential to precipitate violence, without violence occurring. It may only be when the predisposing trait “avoid abandonment” is triggered in addition to “unstable relationships” that interpersonal difficulties, emotional dysregulation and/or impulsivity may escalate and aggregate to result in violence perpetration. This may account for domestic violence that was deemed to be of the “impulsive type” or “borderline” type described by Cunha and Gonçalves [7]. An alternative example to illustrate this could be of an individual with the predisposing trait “sense of entitlement”. It is only when this is triggered by a sense of feeling violated that violence may occur as concluded by Fisher and Hall [18].
This model emphasises that individuals may present with any of the predisposing traits and not exhibit violence. It is instead the interplay of the predisposing traits with the precipitating factors that amount to an increase in risk of violence. As such, formulations of violence in the context of PD diagnoses should be very context specific, considering how each trait may or may not independently and collectively result in violence. This supports and highlights the importance of idiosyncratic formulation in structured professional judgement risk assessments, as used in the HCR-20; which considers previous violence, the specific individual factors present and their interplay, as opposed to a standardised checklist approach, more fitting with an actuarial risk approach.
Idiosyncratic risk factors are vulnerable to changes in circumstance which can subsequently impact on an increase and decrease in risk. With the first example mentioned earlier, the loss of a loved one or a breakdown in relationship may increase risk of violence via triggering “avoid abandonment” and subsequent emotional arousal, whereas stable relationships may be protective against such vulnerability and minimise the risk of violence. Increased support in the areas of idiosyncratic risk factors can therefore impact on managing levels of risk and enhancing dynamic risk management under changes in circumstance. Transparent, collaborative assessment and formulation of idiosyncratic risk factors can raise service user insight and awareness, enhance trust and working alliance [25], support their ongoing self-management and consequentially minimise risk of violence towards others.
Recommendations
The evidence base surrounding Cluster B PDs and risk is presently limited. Evidence is also sparse regarding specific Cluster B NPD traits, which could be further researched. This review proposes a theoretical model for formulating risk of violence, which may be enhanced via future replication of the present methodology in reviewing Cluster B diagnostic traits and risk in the context of sexual violence. The review highlights the importance of idiosyncratic risk factors associated with PD diagnostic traits, which could provide a theoretical basis for further development of PD specific violence risk assessment.
It should be noted that a large majority of the studies included in this review involve individuals who have already been involved in violence. This makes it difficult to discount the impact of financial, social and cultural factors that may impact on the likelihood of violence and reflects the relative dearth of literature currently available linking specific PD symptoms and violence. Further research within different social/subcultural settings not related to violence would be recommended.