Childhood maltreatment and borderline personality organization: The mediating roles of attachment and mentalizing

Child maltreatment (CM) is a well-documented risk factor for borderline personality organization (BPO), a personality structure characterized by identity diffusion, primitive defences, and largely intact but unstable reality testing. BPO is associated with long-term functional impairments. From a developmental psychopathology perspective, BPO may emerge through the interplay of insecure attachment and impaired mentalizing, both shaped by early adversity. However, research on mechanisms linking CM to BPO remains limited. This study examined the mediating roles of adult attachment dimensions and mentalizing in the association between CM and BPO, using an online community sample of 412 participants (M = 25.30; 311 female, 101 male). Participants completed the Childhood Trauma Questionnaire–Short Form (CTQ-SF), Experiences in Close Relationships–Revised (ECR-R), Mentalization Scale (MentS), and Borderline Personality Inventory (BPI). Serial multiple mediation analyses revealed that both (a) attachment anxiety and mentalizing, and (b) attachment avoidance and mentalizing, sequentially mediated the relationship between CM and BPO. These findings support the rationale for mentalization-based interventions. They underscore the importance of enhancing mentalizing within therapeutic settings that foster secure attachment, particularly for individuals with BPO who have experienced CM. However, the cross-sectional design limits causal inference, and future research should use longitudinal designs.