Description of the condition

Borderline personality disorder (BPD) is a condition first recognised in the 20th century (Gunderson 2009). Historically, the term BPD was coined by Adolph Stern to describe a condition in the 'borderland' between psychosis and neurosis (Stern 1938). Subsequent psychoanalytic contributions (especially that of Kernberg 1975) have reaffirmed this distinction, emphasising that the capacity to test reality remains grossly intact but is subject to subtle distortions, especially under stress.

According to current diagnostic criteria, BPD is characterised by a pervasive pattern of instability in affect regulation, impulse control, interpersonal relationships, and self‐image (APA 2013; WHO 1993). Clinical hallmarks include emotional dysregulation, impulsive aggression, repeated self‐injury, and chronic suicidal tendencies (Fonagy 2009; Lieb 2004). Whereas some authors have suggested that it is a variant of affective disorders (Akiskal 2004), others claim that it is only the causes of these diseases that partially overlap in BPD (Paris 2007). Despite the difficulties in defining and delimiting the condition, BPD is still being widely researched. Its importance stems from the considerable psychological suffering of the persons concerned (Stiglmayr 2005; Zanarini 1998), the debilitating functional impairments (Gunderson 2011a; Gunderson 2011b; Niesten 2016; Skodol 2002; Soeteman 2008b), and from the significant impact it has on mental health services (Cailhol 2015; Hörz 2010; Soeteman 2008a; Tyrer 2015; Zanarini 2004; Zanarini 2012).

The definition of BPD in the Diagnostic and Statistical Manual of Mental Disorders (DSM), Fifth Edition (DSM‐5; APA 2013), Fourth Edition Text Revision (DSM‐IV‐TR; APA 2000), and Fourth Edition (DMS‐IV; APA 1994) comprises nine criteria that cover the features mentioned above. At least five criteria should be met for a definite categorical BPD diagnosis to be made, and four criteria for probable diagnosis (see Appendix 1). In the alternative diagnostic classification system of the World Health Organization (WHO), the International Classification of Diseases, which is currently in its tenth edition (ICD‐10; WHO 1993), the relating condition is referred to as "Emotionally unstable personality disorder (F60.3)", of which there is an impulsive type (F60.30) and a borderline type (F60.31; see Appendix 2). The latter essentially overlaps with the DSM‐IV definition. There are 10 possible criteria defined, which very closely reflect the DSM criteria, with the exception of one criterion not included in DSM ("4. Difficulty in maintaining any course of action that offers no immediate reward"; WHO 1993). Out of 10 possible criteria at least five must be met, one of which must be "a marked tendency to quarrelsome behaviour and to conflicts with others, especially when impulsive acts are thwarted or criticised".

The prevalence of BPD in the general population is about 1.5% (Torgersen 2012). In clinical populations, BDP occurs frequently (Munk‐Jørgensen 2010), with studies reporting a prevalence ranging from 9.3% to 46.3% and a mean point prevalence across the studies of 28.5% (Torgersen 2012). Though BPD is predominantly diagnosed in women (75%; APA 2000; APA 2013), it is estimated to be equally frequent in men (Lenzenweger 2007; Ten Have 2016; Torgersen 2001; Torgersen 2012). BPD commonly co‐occurs with mood disorders, substance use disorder, eating disorders, post‐traumatic stress disorder (PTSD), attention‐deficit hyperactivity disorder (ADHD), and is also associated with other personality disorders (Coid 2006; Lenzenweger 2007; Stepp 2012; Storebø 2014; Tomko 2014). Suicidal behaviour is reported to occur in up to 84% of people diagnosed with BPD (Goodman 2012; Soloff 2002), and comorbid mood disorders or substance use disorders are the most common risk factors associated with successful suicide attempts (Black 2004; Doyle 2016; Yen 2004).

Although the short‐ to medium‐term outcome of BPD is poor, there is some evidence that long‐term follow‐ups show a more favourable course, with remission rates of about 85% to 88% within 10 years (Gunderson 2011b; Zanarini 2007). Here, however, remission only means that diagnostic criteria are not fulfilled and does not indicate the absence of any symptoms. Indeed, whereas acute symptoms — such as self‐mutilation, help‐seeking suicide threats or attempts and impulsivity — in most cases decrease with time, affective symptoms reflecting areas of chronic dysphoria, such as chronic feelings of emptiness, intense anger or profound abandonment, largely remain (Zanarini 2007). Therefore the majority of people with BPD still have significant levels of symptoms and experience severe and persistent impairment in social functioning (Kongerslev 2015; Ng 2016). Risk factors for a poorer, long‐term outcome are comorbid substance use disorders, PTSD, and anxiety cluster disorders (Zanarini 2005; Zanarini 2007), as well as a family history of psychiatric disorder (especially mood disorders and substance use disorders), demographic issues such as older age, longer treatment history, pathological childhood experiences, temperament issues and adult psychosocial functioning (Chanen 2012; De Fruyt 2014; Kongerslev 2015; Zanarini 2007). It is estimated that about 60% to 78% of people diagnosed with BPD attempt suicide (Links 2009), though the rate of completed suicides is far less. Zanarini and colleagues found suicide rates of 4.5% during a 16‐year follow‐up (Zanarini 2015b), whereas Stone 1993 reported a suicide rate of 8.5% after 16.5 years. Study estimates of the lifetime risk of suicide among people diagnosed with BPD range from 3% to 10% (Links 2009).

People with BPD have difficulties achieving and maintaining vocational and social functioning over time (Zanarini 2010). Furthermore, treatment‐seeking people with personality disorders, such as BPD, pose a high economic burden on society (van Asselt 2007). Effective treatments could potentially decrease the high costs associated with the condition (Soeteman 2008a).The problem of deliberate self‐harm is also a particular issue within this group (Ayodeji 2015; Kongerslev 2015; Linehan 1997; Rossouw 2012). In medical settings, people diagnosed with BPD often present after self‐harming behaviour or in suicidal crisis and are treated in emergency settings, often involving repeated psychiatric hospitalisations (Cailhol 2015).

In summary, BPD is a condition that has been extensively studied. It has a major impact on health facilities as those affected often present in crisis. Recovery from symptoms or functional impairment (or both) was previously considered likely for only a low percentage of people diagnosed with BPD. However, the long‐term course, in terms of symptomatic recovery, is favourable (Zanarini 2012). Nonetheless, people diagnosed with BPD continue to have considerable interpersonal and functional problems, and sustainable recovery appears difficult to attain (Biskin 2015; Kongerslev 2015; Rossouw 2012).

Description of the intervention

About three quarters of people with BPD present to mental health care professionals (Tomko 2014), and they are even more likely to do so than people with mood, anxiety, or other personality disorders (Ansell 2007). Most will receive psychological interventions (Goodman 2010; Tomko 2014), and often for relatively long periods of time (e.g. for a period of one year or longer) (Ansell 2007; Zanarini 2015a).

A broad range of therapies exist for BPD. The therapy can be either individual or in a group, or a combination of these two treatment modalities. As for most other mental disorders, the psychological interventions can be based on the traditional, major psychotherapeutic schools, such as psychodynamic psychotherapy, cognitive behaviour therapy (CBT) or client‐centered/humanistic therapy. In addition, several specific treatment approaches have been developed within recent decades to meet the challenges of BPD treatment (Bateman 2015). These disorder‐specific approaches are usually precisely structured and manualised (Bateman 2015). Strategies are provided for addressing interpersonal challenges, such as emotional dysregulation and impulsivity, which are core problems for people diagnosed with BPD and could lead to difficulties in forming a therapeutic alliance. Most BPD‐specific psychological interventions involve multimodal therapy, treatment contracts, actively taking measures to minimise premature non‐completion of treatment, providing a crisis intervention protocol and encouraging the patients' sense of agency (Bateman 2015; Clarkin 2012; De Groot 2008; Kongerslev 2015; Livesley 2012; Weinberg 2011). They are typically highly focused on affect and the therapeutic relationship, with a relatively active therapist implementing interventions within a supportive and validating atmosphere (Bateman 2015; Clarkin 2012; De Groot 2008; Kongerslev 2015; Livesley 2012; Weinberg 2011).

Among the specific psychological interventions for people diagnosed with BPD, the most commonly used are: transference‐focused therapy (Clarkin 1999; Yeomans 2015), mentalisation‐based treatment (Bateman 2004; Bateman 2006; Bateman 2016), dialectical behaviour therapy (Linehan 1993; Linehan 2015), cognitive analytic therapy (Chanen 2014; Ryle 1997), schema‐focused therapy (Arntz 2009; Young 2003), and the systems training for emotional predictability and problem solving (Black 2009). Most of these treatments are designed as outpatient treatments of 6 to 24 months duration with 1‐ or 2‐weekly individual sessions. Some also include additional group therapy sessions, inpatient or day‐hospital therapeutic community treatment and psychoeducation.

Broadly speaking, psychodynamic therapies aim to help their patients understand and reflect on their inner mental processes and make links between their past and current difficulties. Treatments based on CBT place emphasis on self‐directed learning processes: patients are encouraged to identify their core beliefs, evaluate and modify their behaviour accordingly, and gain new experiences.

Dialectical behavioural therapy (DBT; Linehan 1993) is a complex psychological therapy that was developed using some of the principles of CBT in combination with mindfulness‐based and Zen‐Buddhistic and dialectical thinking strategies. It aims to change behaviour and enhance the ability to tolerate difficult or painful feelings by focusing on improving skills in stress tolerance, emotion regulation, interpersonal behaviour, and mindfulness.

Mentalisation‐based therapy (Bateman 2004; Bateman 2016) is a complex psychodynamic and attachment‐based psychological therapy programme that aims to increase the reflective functioning or mentalising capacity of the individual, helping the person to understand and recognise the feelings they evoke in others and the feelings they experience themselves, as well as improving the capacity for emotion regulation in interpersonal relations.

Schema‐focused therapy (SFT; Young 2003) draws from both cognitive‐behavioural and psychoanalytic theories and helps people with BPD to identify their self‐defeating core themes arising from unmet emotional needs in childhood and presenting as maladaptive coping styles in adulthood. The goal of SFT is to aid patients in getting their needs met in adaptive ways.

Transference‐focused psychotherapy (TFP; Clarkin 1999) strives to achieve integrated representations of self and others, modification of primitive defence operations, and resolution of identity diffusion by analysis of the transference within the therapeutic relationship. Primitive object relations, which can be polarised and split, may be transformed to advanced or mature object relations characterised by more integrated object relations. TFP relies on techniques of clarification, confrontation and transference interpretation within the relationship between patient and therapist.

Cognitive analytic therapy (Ryle 1997) assumes that people with BPD typically experience rapid switching from one self‐state to another in a dissociate manner. The aim is to work with the patient cognitively to identify procedural sequences, chains of events, emotions, thoughts and motivations to understand how a target problem (like self‐harm) is established and maintained, and to identify reciprocal roles (i.e. how early experiences are replayed later in life).

The systems training for emotional predictability and problem solving (Black 2009) combines group‐based psychoeducation with skills training, and targets biased social cognition driven by cognitive filters or schemas.

Relaxation techniques and patient education programmes will be considered their own intervention class (i.e. not CBT or psychoanalytically based), as long as they are not explicitly grounded in or taken from a specific treatment approach (such as psychoeducation according to the DBT approach, CBT, or the SFT approach, etc.).

How the intervention might work

Evidence‐based psychological therapies are based on assumptions about causality, core symptoms, and maintenance of the disorder (Kazdin 2004; Livesley 2003; Livesley 2004). The various psychotherapeutic approaches to BPD claim different mechanisms of action according to their respective models of disease causation (Huprich 2015; Livesley 2004; Livesley 2016). However, they also contain a number of common elements that can account for why a number of seemingly different approaches appear to be effective in ameliorating BPD symptoms (Bateman 2015; Fonagy 2014; Kongerslev 2015; Weinberg 2011), including: a clear and highly structured treatment framework; an explicit model of BPD symptomatology; a consistent focus on the therapeutic relationship, affect regulation, tolerance of emotional states, and biases in social cognition; a high priority given to self‐harm and suicidal behavior; active therapists who deliver both support and validation as well as explorative and change‐oriented interventions; mix of treatment formats (e.g. includes both individual and group therapy); and therapist support in the form of supervision and regular meetings. Following Weinberg 2011:

1. 'emotional dysregulation' (e.g. intense anger and affective instability) is addressed through attention to affect, including raising awareness of emotional states, their triggers, and enhancing tolerance and regulative strategies;

2. 'behavioral dysregulation' (e.g. impulsivity, self‐harm and suicidal behaviours) is addressed through change‐oriented interventions including, for example, challenging negative thoughts, skills training, behavioral experiments, praise, and limit setting; and

3. 'interpersonal dysfunction' (e.g. unstable relationships and stress‐related paranoid ideation) is treated using interventions that enhance the social‐cognitive (or mentalising) capacities of the BPD patient, through making basic and often negatively biased automatic assumptions explicit and more realistic or adaptive, and through paying attention to the establishment and maintenance of a safe and sound working alliance within the therapy sessions.

There is a risk that psychological therapies might not be helpful for all patients, either due to the interventions delivered or through factors in the relationship between the patient and therapist (Kongerslev 2015; Lilienfeld 2007; Parry 2016), and very little research has been done on this in patients with BPD. The effectiveness of the therapy depends on the skills of the therapist to create the possibility for change with each patient. There is, therefore, the added complexity that the relationship or working alliance between the therapist and the patient is itself an ‘active ingredient’ of the therapy and that the quality of this relationship is an important predictor of outcome (Horvath 2011; Norcross 2011). There is no guarantee that the therapy will deliver what was specified in the manual or what was investigated in a randomised clinical trial (Parry 2016).

Finally, it should be noted that the highly structured treatment organisation, including regular meetings between staff to discuss patients as well as supervision and managerial support to staff, is presumably important not only for the provision of effective psychological therapy for persons diagnosed with BPD, but also in order to prevent iatrogenic harm (Hutsebaut 2012).

Why it is important to do this review

People with BPD and their family and friends experience high levels of psychological suffering. Moreover, BPD is associated with considerable social costs in terms of service use (e.g. presentation to emergency clinics due to self‐harm or suicidal crises and repeated hospitalisations) and poor psychosocial functioning (e.g. inability to complete education or get/maintain a job). Against this background, identification of effective psychological therapies for BPD is important.

Our review aims to provide a systematic summary of the evidence from randomised controlled trials (RCTs) in order to help people with BPD, their family and friends, mental health care workers, and policy and decision managers in general, to make informed decisions about evidence‐based treatment for BPD.

This is a protocol for an update of the two previous Cochrane Reviews on psychological therapies for BPD (Binks 2006; Stoffers‐Winterling 2012). In addition to updating the former Cochrane Reviews, our study also seeks to address some of methodological limitations of both past and current reviews (Bateman 2015; Cristea 2017; Kliem 2010), by publishing a protocol for our review and using a broad and updated search strategy.