BackgroundBorderline personality disorder (BPD) is the prototypical disorder of emotion dysregulation. We have previously shown that patients with BPD are impaired in their capacity to engage cognitive reappraisal, a frequently employed adaptive emotion regulation strategy. MethodsHere, we report on the efficacy of longitudinal training in cognitive reappraisal to enhance emotion regulation in patients with BPD. Specifically, the training targeted psychological distancing, a reappraisal tactic whereby negative stimuli are viewed dispassionately as though experienced by an objective, impartial observer. At each of 5 sessions over 2 weeks, 22 participants with BPD (14 female) and 22 healthy control participants (13 female) received training in psychological distancing and then completed a widely used picture-based reappraisal task. Self-reported negative affect ratings and functional magnetic resonance imaging data were acquired at the first and fifth sessions. In addition to behavioral analyses, we performed whole-brain pattern expression analyses using independently defined patterns for negative affect and cognitive reappraisal implementation for each session. ResultsPatients with BPD showed a decrease in negative affect pattern expression following reappraisal training, reflecting a normalization in neural activity. However, they did not show significant change in behavioral self-reports. ConclusionsTo our knowledge, this study represents the first longitudinal functional magnetic resonance imaging examination of task-based cognitive reappraisal training. Using a brief, proof-of-concept design, the results suggest a potential role for reappraisal training in the treatment of patients with BPD.