• adolescent;
  • assessment;
  • borderline personality disorder;
  • treatment

Sizeable numbers of youth in community and clinical settings meet diagnostic criteria for borderline personality disorder (BPD). Early assessment and treatment may positively alter the life-course trajectory of young people with BPD and reduce future suffering and impairment. This article reviews the potential etiological bases of BPD, including genetic, neurobiological, social-cognitive, and the biosocial theory. Prospective, retrospective, and correlational research including infant and child temperament, internalizing and externalizing psychopathology, as well as suicidal and nonsuicidal self-injurious behaviors provide additional information to better understand potential risk factors for the development of BPD as well as points for intervention (e.g., emotion regulation). To date, dialectical behavior therapy and mentalization-based treatment appear promising as effective treatments for adolescents who carry at least three borderline personality features in addition to self-harm. Directions for future research are discussed.