The goal of this pre-post-follow-up study is to examine how well the treatment Dialectical behavior therapy for adolescents (DBT-A) with a duration of 20 weeks for adolescents with self-harm and suicidal behavior works in routine clinical practice. The main questions it aims to answer are:

• to investigate how well DBT-A works after treatment and at 3-month follow-up, measured by episodes of self-harm, suicide attempts, depressive symptoms and quality of life, drop-out from treatment and number of possible participants who decline DBT-A.
• to investigate how well DBT-A works at 12 months follow-up
• to investigate whether pre-treatment factors can predict who will benefit from treatment

Self-harm and suicidal ideation are prevalent among adolescents and associated with major mental health problems and adverse life events. Dialectical behavior therapy for adolescents (DBT-A) is an empirically supported treatment for self-harm and suicidal ideation in adolescents. However, knowledge is scarce on the effectiveness, long-term outcomes, acceptability, and dropout of DBT-A when implemented and delivered as part of routine clinical practice in the Norwegian national health care system. The main aim of this study is to examine the outcomes from DBT-A in terms of self-harm episodes, suicide attempts, and emergency hospital admission, in addition to acceptability and dropout, when DBT-A is delivered at the Department of Child and adolescent psychiatry (PBU), Haukeland University Hospital (HUS). The study is an uncontrolled pre-post study with one-year follow-up and includes three aims: to evaluate outcomes of DBT-A up to three months post-treatment, at one-year follow-up, and to describe predictors of outcome for adolescents receiving DBT-A.

Inclusion Criteria:

• Age 13-18 years
• Ongoing or a history of self-harm the last six months; current suicidal behavior (suicidal thoughts or at least one suicide attempt within the previous six months); at least three criteria of Diagnostic and Statistical Manual -5 (DSM-5) Borderline personality disorder (BPD), or the self-destruction criterion of DSM-5 BPD in addition to minimum two subthreshold criteria as assessed by the Structured Clinical Interview for DSM-5 Personality Disorders (SCID-5-PD) (First et al., 2016)
• Fluency in Norwegian
• One parent/trusted adult that can participate together with the adolescent.

Exclusion Criteria:

• Intellectual disability
• Significant learning or language impairments
• Autism spectrum disorder
• Anorexia Nervosa
• Any psychotic disorder
• Substance abuse disorder. These patients will be offered treatment as usual at their local outpatient clinic.

An independent evaluator will assess participants at post treatment and one year follow-up. Due to the single group design, the assessor will be aware that participants have received the intervention, but will not be involved in recruitment and treatment.