Maladaptive defense mechanisms moderate treatment outcome in 6 months versus 12 months dialectical-behavior therapy for borderline personality disorder

Abstract

Objective: We investigated whether defense mechanisms in patients with borderline personality disorder (BPD) predict treatment response of dialectical behavior therapy (DBT) and whether they moderate outcome in different treatment lengths. Method: We analyzed a subsample of 60 outpatients with BPD, randomized into either 6 (n = 30) or 12 (n = 30) months of DBT. The average level of defensive adaptiveness, assessed with observer-rated overall defensive functioning (ODF) and “immature” (i.e., maladaptive) defenses were used as predictors and moderators of self-reported frequency of self-harm. We conducted a Generalized Linear Mixed Model (GLMM). Results: A lower ODF at treatment onset predicted smaller reductions in self-harm, irrespective of treatment length (IRR = 0.92, 95% CI = [0.86, 0.99], p =.020). Lower order “immature” (“major image distorting”) defenses showed significantly smaller (IRR = 1.13, 95% CI = [1.06, 1.21], p