In recent years, studies led by investigators at the University of Pittsburgh have emerged that demonstrate the promise of adapting dialectical behavior therapy (DBT) to align with the unique needs of youth with bipolar disorder (BD). Our group has conducted a dissemination and implementation DBT study at Sunnybrook Health Sciences Centre focused specifically on youth with BD. Preliminary data from that study demonstrate that the study therapists, now at CAMH, have achieved fidelity and competence in delivering the intervention, as evidenced by adherence coding scores and participant outcomes. The DBT intervention is based on Miller et al.'s DBT for suicidal adolescents, with modifications for youth with BD. A co-investigator on this study, Dr. T. Goldstein, developed and refined the manualized treatment during her National Institute of Mental Health K23 award in consultation with Dr. Miller. In keeping with the protocol implemented in prior studies, DBT in the present study will be conducted over 1 year, and divided into two modalities: 1) DBT skills training (approximately 60 minute biweekly meetings); and 2) DBT individual therapy sessions (approximately 60 minute biweekly sessions) alternating with skills training. Family involvement in skills training will be strongly encouraged, but not mandatory. Master's level therapists with clinical experience in youth with BD and their families will conduct DBT. This study includes 1 year of assessments (intake, 3, 6, 9, and 12 months) while the intervention is being delivered. The target sample size will be 60 youth with and/or at familial risk for BD ranging from 13 to 23 years of age. The current study endeavors to build upon the knowledge base in this area by offering DBT to youth with and/or at familial risk for BD at CAMH with an emphasis on predictors and mediators of treatment outcomes, with the eventual goal of personalizing treatment selection and delivery. While DBT bodes favorably as a treatment for youth with BD, the literature in this area remains sparse. Moreover, the investigators do not yet understand what clinical characteristics and pre-treatment variables predict and mediate treatment outcomes. There is substantial between-person and within-person variability among youth with and/or at familial risk for BD in terms of risk indicators, type and severity of symptoms, associated distress, and compounding functional impairment. The current study proposes to move beyond questions of efficacy toward identifying individual characteristics that are differentially associated with response to DBT. Identification of baseline demographic and clinical characteristics that are associated with response to DBT (i.e., predictors), as well as time-varying characteristics during the course of treatment (i.e., mediators), could guide iterative optimization of DBT through individualized modifications. Patient engagement will be sought through consultation forums after they have completed the study. Overall, this research endeavors to begin to examine the patient factors that predict and mediate an individual's response to DBT, with important questions to consider, such as: For which youth with and/or at familial risk for BD does this intervention have the greatest effect? Does the intervention have similar effects across sub-groups of youth with BD? The investigators anticipate that the identification of predictor and mediating variables has the potential to inform the iterative personalization of DBT for youth with and/or at familial risk for BD in the future, including content, timing, and relative emphasis on various aspects of DBT (e.g., psychoeducation, skills, individual sessions, family involvement, phone coaching).