What is the bottom line regarding successful treatment of borderline personality disorders?

Within the general population, approximately 30% of individuals with BPD meet criteria for PTSD and approximately 25% of individuals with PTSD meet criteria for BPD (Pagura et al., 2010; Pietrzak, Goldstein, Southwick, & Grant, 2011). Within clinical BPD samples, rates of comorbid PTSD are estimated to range from 30 to 80% (e.g., Harned et al., 2010; Zanarini, Frankenburg, Hennen, Reich, & Silk, 2004). Compared with either disorder alone, BPD-PTSD is associated with higher comorbidity of additional mental health disorders, as well as greater symptom severity and healthcare burden (Jowett, Karatzias, & Albert, 2019; Pagura et al., 2010; Scheiderer, Wood, & Trull, 2015). Compared with BPD alone, BPD-PTSD is associated with more severe BPD symptomatology (Barnicot & Crawford, 2018), general psychological distress (e.g., Boritz, Barnhart, & McMain, 2016), self-harm (e.g., Barnicot & Crawford, 2018; Cackowski, Neubauer, & Kleindienst, 2016; Harned et al., 2010), suicidal behaviours (e.g., Cackowski et al., 2016; Pagura et al., 2010), and lower rates of remission from BPD (e.g., Keuroghlian et al., 2015; Zanarini et al., 2004). Similarly, compared to individuals with PTSD alone, research has found that those with BPD-PTSD have greater PTSD symptom severity, poorer quality of life, and increased suicidality (e.g., Pagura et al., 2010). Individuals with BPD-PTSD are also especially likely to utilize mental health and emergency services (Connor et al., 2002; Scheiderer et al., 2015). Given the personal and public health impact of BPD-PTSD, it is imperative to identify optimally effective and efficient methods of treating these individuals.

First-line psychotherapeutic treatments have been established for the treatment of BPD and PTSD independently. BPD-specific treatments, which prioritize stabilization and target life-threatening behaviours, such as self-harm and suicide attempts, typically by increasing patients' capacity to regulate or tolerate emotion, are recommended for treating BPD (Choi-Kain, Albert, & Gunderon, 2016; Paris, 2009). There is considerable empirical support demonstrating that these treatments are efficacious in reducing symptoms of BPD (e.g., suicidal and self-injurious behaviour; Cristea et al., 2017; DeCou, Comtois, & Landes, 2019). Dialectical behaviour therapy (DBT; Linehan, 1993) is the most researched intervention for BPD, with a large number of randomized controlled trials (RCTs) providing support for its efficacy (e.g., Linehan et al., 2006, Linehan et al., 2015). Several RCTs have also provided support for mentalization-based treatment (Bateman & Fonagy, 2006) in reducing BPD symptoms and suicidal and self-injurious behaviours (e.g., Bateman, Constantinou, Fonagy, & Holzer, 2020; Bateman & Fonagy, 2009). Finally, emotion regulation group therapy (Gratz & Gunderson, 2006) has been tested in one RCT (Gratz, Tull, & Levy, 2014) and several uncontrolled trials (e.g., Sahlin et al., 2017) that have shown significant decreases in self-harm and BPD symptoms among individuals with BPD and subclinical BPD. In contrast to BPD-specific treatments, trauma-focused treatments, which target trauma-related memories and emotions (Ehlers et al., 2010), are recommended as front-line treatments for PTSD (e.g., American Psychological Association, 2017; Bisson et al., 2019; Lee et al., 2016). A large number of RCTs have provided empirical support for trauma-focused treatments, including prolonged exposure (PE; Foa, Hembree, & Rothbaum, 2007), cognitive processing therapy (CPT; Resick, Monson, & Chard, 2017), eye movement desensitization and reprocessing (EMDR; Shapiro, 2018), and narrative exposure therapy (NET; Schauer, Neuner, & Elbert, 2011) in the reduction of PTSD symptoms (see Lee et al., 2016 for a review).

Importantly, BPD-specific and trauma-focused treatments differ in what they prioritize (i.e., decreasing self-harm and suicidal behaviours, stabilization, and emotion regulation skills training vs. trauma processing, respectively) and, when BPD and PTSD co-occur, there is a lack of consensus as to which treatment is most appropriate. It is also unclear how the comorbid diagnosis that is not directly targeted by these interventions (e.g., PTSD for BPD-specific treatments and BPD for trauma-focused ones) impacts the primary outcomes. Further, BPD and PTSD interventions have also been combined, typically by sequentially delivering BPD-specific treatment followed by trauma-focused treatment (i.e., stage-based approach; e.g., Bohus et al., 2013; Harned, 2013). Harned (2014) reviewed these treatment approaches for BPD-PTSD and concluded that it is safe and efficacious to deliver stage-based treatment to individuals with BPD-PTSD. However, since publication of this article, several BPD-PTSD treatment studies have been conducted. Furthermore, to date, there has not yet been a systematic review that identifies potential BPD-PTSD treatment approaches, their outcomes, and safety, obfuscating whether and how this comorbidity may be optimally treated. Therefore, we provide an updated and expanded systematic review of BPD-PTSD treatment focused on examining: (a) available BPD-PTSD treatment approaches; (b) when only one of these disorders is targeted, the impact of the comorbid diagnosis on the primary outcomes and the intervention on the comorbidity; (c) the impact of the stage-based approaches on both BPD and PTSD treatment outcomes; and (d) safety considerations across these modalities.

Protocol

This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (Moher, Liberati, Tetzlaff, Altman, & Prisma Group, 2009).

Inclusion and exclusion criteria

Studies were included based on the following criteria: 1. The sample had BPD or subclinical BPD and PTSD or subclinical PTSD according to Diagnostic and Statistical Manual of Mental Disorders (DSM)-III-R, DSM-IV, or DSM-5 diagnostic criteria or a validated measure; 2. The study involved the