Predictors, moderators and mediators of psychosocial treatment outcomes in borderline personality disorder: a systematic review (part I - patient related factors)

Abstract Background The most recent systematic review of predictors of treatment response in borderline personality disorder (BPD) was conducted in 2012. Since that time several new studies have been conducted and so the objective of this review is to conduct a more current systematic review of predictors, mediators and moderators of psychosocial treatment outcomes for individuals diagnosed with borderline personality disorder (BPD). Methods MEDLINE, EMBASE, Psychinfo, Web of Science and CINAHL were systematically searched for articles outlining the effects of psychosocial treatments for individuals diagnosed with BPD across treatment modalities. Studies in which the only treatment was pharmacological were excluded. PRISMA guidelines were followed. Articles reporting the effect of predictors, moderators, mediators on psychosocial treatment outcomes in this population were synthesized. Results This search identified 18,973 unique articles of which 311 studies met the inclusion criteria for this systematic review. Due to the large number of articles identified, studies of patient-related predictors are reported here, while studies of treatment-related predictors will be reported in a subsequent paper. Demographic variables (ex: age, gender, education, employment) as well as co-morbid mental health conditions (substance use disorder, major depressive disorder, anxiety disorders) appeared not to be associated with change in BPD symptoms or drop out. Findings with regards to BPD symptoms at baseline as a predictor of change in BPD symptoms at follow up were mixed. Mindful “non-judging” and emotion regulation showed promise as predictors and mediators of improvement in BPD symptoms. Meta-analysis was not conducted due to the heterogeneity of methodologies used in the studies. Conclusion The current review identified several key variables that are unlikely to be predictors of outcome across treatments for individuals with BPD. Many studies in the review examined unique predictor-outcome pairs resulting in little replication. Further replication and identification of predictors may aid in refinement of treatment development and implementation for this population. Trial registration Pre-registered March 2020 in the PROSPERO International Prospective Register of Systematic Reviews (CRD42020173948).