The relation between mindfulness and mentalizing among individuals with borderline personality disorder: A controlled study

Mentalizing-the capacity to consider mental states-is a core human ability, yet processes related to it remain poorly understood. Mindfulness has been proposed as functionally related to mentalizing, but the nature and direction of this relation remain unclear. Although both are relevant to borderline personality disorder (BPD), research has rarely examined them together. This study examined group differences in and associations between dispositional mindfulness and mentalizing among individuals with BPD, psychiatric controls (PCs), and healthy controls (HCs). Participants were 153 adults (51 per group) completing diagnostic and laboratory assessments. Mindfulness was measured with the Five Facet Mindfulness Questionnaire, and mentalizing with the Mentalization Scale and Reflective Functioning Scale applied to the Brief Reflective Function Interview. The BPD group showed markedly lower mindfulness than PCs and HCs (ds = 0.80-2.40, ps < .001). Self-reported mentalizing differences were smaller: BPD participants scored lower than HCs (d = -0.51), but not PCs. Observer-rated mentalizing showed no overall group effect; the BPD group scored lower than PC in planned comparisons. Mindfulness was positively associated with self-reported mentalizing (p < .001), but not with observer-rated mentalizing (r = .03, p = .69). Mindfulness impairments were particularly pronounced in BPD, whereas mentalizing differences were smaller and varied across methods. Self-reported mindfulness and mentalizing were positively associated, underscoring the value of examining directionality and functional relations while explicitly integrating mindfulness into theoretical models of BPD. (PsycInfo Database Record (c) 2026 APA, all rights reserved).