 Therefore, the primary aim of this proposal is to examine the efficacy of an abbreviated course of DBT including all components of treatment compared to the evidence-supported 12 months of DBT. Our principal question is: How do the clinical outcomes of 6 months of DBT DBT-6 compare with the standard 12 months DBT-12 for the treatment of chronically self-harming individuals with BPD? Assessments will be conducted at pretreatment and at 3-month intervals until 24 months i.e., 3, 6, 9, 12, 15, 18, 21, and 24 months. 