Mentalization, Emotional Dysregulation, and Emotion-Related Impulsivity in Young Adults with Borderline Personality Disorder.

Background: Borderline personality disorder (BPD) is characterized by emotional dysregulation and emotion-related impulsivity, particularly during late adolescence and early adulthood. Although mentalizing difficulties have been proposed as an important mechanism underlying borderline psychopathology, their contribution to emotion-related impulsivity beyond alexithymia and anxiety-depressive symptoms remains unclear. This study examined the relationships among mentalizing difficulties, emotional dysregulation, and emotion-related impulsivity in young individuals with BPD. Methods: A total of 166 participants aged 16-25 years were recruited in French-speaking Belgium, including 45 individuals with DSM-5 BPD and 121 non-clinical controls. Mentalization was assessed using the Reflective Functioning Questionnaire (RFQ-8), emotional dysregulation using the Difficulties in Emotion Regulation Scale (DERS), impulsivity using the UPPS-P Impulsive Behavior Scale, and alexithymia using the Toronto Alexithymia Scale (TAS-20). Group comparisons, quantile regressions, Spearman correlations, and adjusted multiple linear regressions were performed. Results: Participants with BPD reported significantly higher uncertainty regarding mental states (RFQu) than controls, and this difference remained significant after adjustment for clinical covariates. RFQu was associated with overall emotional dysregulation, particularly difficulties in behavioral control under distress, and with emotion-related impulsivity, especially negative urgency. Associations between RFQu and negative urgency remained significant after controlling for alexithymia, depressive symptoms, trait anxiety, and borderline status. Corresponding associations with positive urgency did not reach statistical significance. Conclusions: Mentalizing difficulties may account for additional variance in emotion-related impulsivity beyond alexithymia and general psychopathological distress. These findings support a developmental, mechanism-focused understanding of emerging BPD and highlight mentalization as a potential target for early intervention and future longitudinal research.