Changes of borderline symptoms, personality functioning, and dysfunctional personality traits after dialectical-behavioral therapy in borderline personality disorder.

Borderline Personality Disorder (BPD) is a complex and debilitating condition characterized by limited treatment response and high dropout rates across treatments, even in leading therapeutic approaches, such as Dialectical-Behavioral Therapy (DBT). Given the heterogeneity of BPD symptomatology and the current shift toward dimensional assessments of personality disorders, this study investigates whether dimensional measures according to the DSM-5's Alternative Model for Personality Disorders (AMPD) may serve as additional markers of treatment outcome and dropout. Eighty-five participants with BPD were recruited from a naturalistic inpatient DBT program. Associations between BPD symptoms (Borderline Symptom List, Borderline Personality Disorder Severity Index), personality functioning (Level of Personality Functioning Scale - Brief Form 2.0), and dysfunctional personality traits (Personality Inventory for DSM-5 and ICD-11 - Brief Form Plus) were examined at baseline, as well as their sensitivity to change after DBT. At baseline, both personality functioning and dysfunctional personality traits, except antagonism, were associated with BPD symptoms (all r ≥ 0.4). After 10 weeks of DBT, parallel improvements were observed in personality functioning and dysfunctional personality traits, with significant reductions in negative affectivity and detachment. Elevated baseline levels of negative affectivity and psychoticism were associated with less BPD symptom change. DBT dropout was linked to higher impairment in negative affectivity and anankastia at admission. Personality functioning showed greater sensitivity to change throughout DBT compared to dysfunctional personality traits. These findings emphasize how AMPD may yield benefits beyond categorical BPD diagnoses, potentially contributing to more personalized and effective treatment planning and preventing dropouts.