RESUMEN
Recent evidence supported the notion that add-on group therapy should be provided to individuals with borderline personality disorder (BPD) who already undergo individual psychotherapy. The present 20 week-study was aimed to evaluate the efficacy of the adjunction of group interpersonal psychotherapy (IPT-G) to individual interpersonal psychotherapy adapted for BPD - revised (IPT-BPD-R) in comparison with individual IPT-BPD-R alone in a group of BPD patients. In addition, demographical and clinical characteristics that can be considered predictors of response to add-on group therapy were investigated. Forty-six patients were randomly assigned to 1) IPT-BPD-R plus IPT-G or to 2) IPT-BPD-R in the waiting list for IPT-G. Patients were assessed at baseline and after 20 weeks with: the Clinical Global Impression Scale, Severity item (CGI-S); the Social Occupational Functioning Assessment Scale (SOFAS); the Satisfaction Profile (SAT-P); the Borderline Personality Disorder Severity Index (BPDSI); the Modified Overt Aggression Scale (MOAS); the Childhood Trauma Questionnaire - Short Form (CTQ-SF); the Inventory of Interpersonal Problems (IIP-32); and the Reading the Mind in the Eyes Test (RMET). Statistical analyses included: ANOVA for repeated measures to compare score changes of the rating scales within groups (trial duration) and between groups (treatment modalities), and multiple regression analysis to identify which clinical factors are significantly and independently related to the difference of BPDSI score between baseline and week 20 (Δ BPDSI). The significance level was P ≤ 0.05. Both significant within-subjects effects (duration) and between-subjects effects (treatment modalities) were found for the following rating scales: MOAS; BPDSI items "feelings of emptiness", "outbursts of anger," and "affective instability"; RMET; SAT-P items "work" and "sleep, food, free time"; and IIP-32 scale "domineering/controlling". At the multiple regression analysis BPDSI item "impulsivity", RMET, and the subscale "socially inhibited" of the IIP-32 were significantly and independently related to Δ BPDSI score. In conclusion, the add-on of IPT-G produced higher improvement in core BPD symptoms, social cognition, a dysfunctional interpersonal style, and subjective quality of life. Subjects who were less impulsive, less socially inhibited, and with higher abilities in social cognition obtained greater benefits from the adjunction of group therapy. CLINICAL TRIALS REGISTRATION NUMBER: ACTRN12623000002684, Australian New Zealand Clinical Trials Registry (ANZCTR).