The aim of this study is to evaluate the effectiveness of a 20-week Dialectical Behaviour Therapy (DBT) skills training group for the treatment of chronic suicidal and non-suicidal self-injurious (NSSI) behaviours in individuals diagnosed with borderline personality disorder (BPD). Previous research has established the effectiveness of a one year comprehensive, combined individual and group DBT treatment. However, in practice, DBT is often offered in a skills only group format. This study will consist of a randomized, controlled trial designed to evaluate the effectiveness of DBT compared to a wait list control. 84 participants will be randomized to the 20-week DBT group or the wait-list and the following outcomes will be assessed:

1. frequency of suicidal and NSSI behaviours
2. symptom distress
3. impulsivity
4. treatment retention
5. skill acquisition and
6. social functioning

Assessments will occur at pre-treatment, 10 weeks, 20 weeks and 3 months post treatment. The following main hypotheses will be examined: (1) Patients in the DBT skills group condition will have superior outcomes to patients on the treatment as usual wait list control in areas targeted by the treatment: frequency of suicidal and NSSI behaviours, emergency room visits, psychiatric hospital admissions, impulsivity, and knowledge and use of behavioral skills, general symptoms. The group receiving DBT will have superior outcomes at post treatment and these outcomes will be maintained during the three month post-treatment follow-up.

The study will consist of a single-blind, two-arm randomized controlled trial designed to evaluate the effectiveness of DBT skills group offered as an adjunct to treatment as usual compared to a wait list control plus treatment as usual. The continuation of treatment as usual in both arms is permitted for two reasons. First, it would be unethical to assign suicidal patients to a wait list condition that prohibited involvement in ongoing treatment. Second, the proposed design enables us to address the question of the additive effect of the DBT skills group intervention. Subjects will be randomized to receive 20 weeks of DBT group skills training plus treatment as usual, or to a wait list control plus treatment as usual. Clinical effectiveness outcomes will be assessed at baseline, at 10 weeks, at 20 weeks and at 8 months follow-up. DBT skills training is a manualized intervention developed by Linehan (1993). Key skills from the modules described in Miller, Rathus, and Linehan (2006) will serve as the basis of the DBT skills group, delivered in a psychoeducational format over the course of weekly two-hour sessions. The skills group covers five modules: mindfulness, emotion regulation, distress tolerance, interpersonal effectiveness, and dialectics.

Inclusion Criteria:

• diagnosis of DSM-IV Borderline Personality Disorder
• 18-60 years of age
• have had two suicidal or non-suicidal self-injurious behaviours in the past five years with one occurring in the past ten weeks
• be literate in English
• provide informed consent to participate in the study.

Exclusion Criteria:

• not meet DSM-IV criteria for a psychotic disorder, bipolar disorder or, dementia
• not have evidence of an organic brain syndrome or mental retardation based on clinical interview
• not participated in DBT treatment during the past year