The effectiveness of psychological interventions for borderline personality disorder for those who misuse substances: a systematic review and narrative synthesis

Purpose - This study aims to identify and critically appraise literature exploring the effectiveness of psychological interventions in improving borderline personality disorder (BPD) symptomatology for individuals whomisuse substances. Design/methodology/approach - Systematic searches across six databases (PsycINFO, Embase, Scopus, Medline, CINAHL and ProQuest), hand searching and citation chaining were conducted between June and August 2021. Key search terms included BPD, substance use, therapy and effect. Study and sample characteristics, interventions, outcome measures and key findings were extracted. Quality assessment and a narrative synthesis approach were used to explore strengths, limitations and relationships between and within studies. Findings - Seven eligible reports were included and showed mostly adequate quality. Mixed samples, designs, outcomes, definitions and implementation varied. Treatment completion did not differ significantly between those who did and did not misuse substances. Interventions demonstrated effectiveness in relation to psychiatric symptoms, hospital admissions, self-efficacy and impulsive and self-mutilating (cutting, burning, etc.) behaviours. No effectswere found for suicidal or parasuicidal (threats, preparation and attempts) behaviours. Research limitations/implications - This review only considers individuals with diagnoses of BPD who are not accessing substance misuse treatment. Radically open dialectical behaviour therapy (DBT), therapeutic communities and other interventions are available as interventions for substance misuse (Beaulieu et al., 2021). Based on the findings of this review, it should not be assumed that such interventions affect substance misuse rather than BPD symptomatology. Therefore, future research might explore the effectiveness of these interventions on BPDsymptomatology despite this not being the primary target for intervention. Practical implications - DespiteMcCrone et al. (2008) noting the cost of this population's difficulties to both themselves and services, the limited number of studies in this area is astonishing. Despite a lack of quality in the data available, there i some evidence to support the use of DBT and general psychiatric management (GPM) interventions for those with BPD and concurrent substance misuse. It is therefore of principal importance that health and social care services action Public Health England's (2017) recommendations. Individuals with coexisting BPD and substance misuse would then receive support from any professional they see, who could then refer for psychological therapies. Originality/value - Although the reports appear to show that DBT, integrated therapies and GPM may be effective for this population, conclusions cannot be drawn with high levels of confidence due to heterogeneity among studies. The findings indicate that future, high-quality research is needed to test the effects of interventions on BPD symptomatology for those who misuse substances. Randomised controlled trials with sufficient statistical power, homogeneous outcomes and standardisedmethodological approaches are needed.