DBT combines behaviour-change strategies from CBT and acceptance strategies from Zen philosophy into an approach that focuses on client validation and behavioural change [716, 717]. Originally developed for the treatment of adults with BPD who were also chronically suicidal, DBT has become the ‘gold standard’ evidence-based treatment for both BPD and suicidality [716, 718, 719]. The primary principles underpinning DBT are increasing interrelatedness synthesising acceptance and change, and teaching coping skills to deal with change [720]. Strategies to address changes in behaviour consist of behavioural analyses, skills training, contingency management, cognitive restructuring, and exposure-based strategies to reduce avoidance. Acceptance strategies include mindfulness and validation. A strong therapeutic alliance and improvements in emotion regulation skills appear to be particularly important for positive treatment outcomes [721, 722]. DBT has been found to be efficacious in treating personality disorders (including those co-occurring with AOD use) [723, 724], AOD use disorders (including those co-occurring with personality disorders) [723, 725], and there is emerging research supporting its use for ED that are co-occurring with AOD use disorders [726, 727] (see Chapter B7).