Standard Dialectical Behavioral Therapy (DBT)is an effective treatment for Borderline Personality Disorder (BPD), particularly for patients with significant behavioral and affective dysregulation, including suicidality. However, DBT in its original format is delivered in 12 months, and even though currently there are shorter versions of the treatment being developed and tested, in the context of public mental health care in Chile a shorter, intensive and lighter version of the treatment is likely needed to help patients seeking help for BPD symptoms. This study will test whether a 3 month, intensive and simplified version of DBT is at least equivalent to standard six months DBT with all its components (skills training, individual therapy, coaching calls, and treatment-team consulting). 120 patients diagnosed with BPD we'll be randomly assigned to receive either the short, intensive 3-month intervention or the longer standard 6-month DBT intervention. Baseline measures will be taken pre-treatment, upon treatment completion, and at a 4-month follow-up. Session-to-session change in BPD symptoms will also be measured throughout the treatments. Primary outcomes for the study are BPD symptoms, frequency, and intensity of suicidal activity. Secondary outcome measures include depression scores, quality of life, and ER visits, and days in inpatient care.

Inclusion Criteria:

• BPD diagnosis according to DSM-IV criteria, evaluated through a SCID-II structured interview.
• History of suicide attempt or self-harm operationalized as at least two episodes of suicide or self-harm in the last 24 months
• Provide signed informed consent to participate in the study.
• Participant has not received more than 8 weeks of DBT in the past 24 months.

Exclusion Criteria:

• Fulfill diagnostic criteria for psychotic disorders classified in ICD-10 (F20-F29), evaluated through the MINI interview.
• Diagnosis of Antisocial Personality Disorder evaluated through the SCID-II.
• Active substance use disorder within the last 3 months, assessed by ASSIST.
• Harmful use or problem dependence on alcohol assessed through AUDIT.
• Meet criteria for Bipolar Affective Disorder type I assessed through the MINI Mania module.
• Significant cognitive impairment assessed through Moca (Moca> 21).
• Diagnosis recorded in the clinical record of intellectual-cognitive disability.
• Recording in the clinical record of medical or surgical problems that could imply a probable hospitalization within one year of the start of the study (for example, cancer, coronary heart disease, etc.).

No plans to share IPD at this point.

Outcome assessors will not be therapists in the study and will be blind to treatment allocation. The only exception involves assessors in charge of evaluating care usage (e.g. ER visits and inpatient) as they will probably find out the treatment condition. These assessors will not participate in the assessment of primary or other secondary outcome measures.