Behavioural Activation for Bipolar Depression

Inclusion Criteria: * scoring in the clinical range on a self-report measure of depression severity (the PHQ-9) meeting diagnostic criteria for depression based on a diagnosis on Diagnostic Interview for Anxiety, Mood, and OCD and Related Neuropsychiatric Disorders (DIAMOND) meeting diagnostic criteria for Bipolar I or II Disorder DIAMOND) participants will require a working knowledge of written and spoken Icelandic, sufficient to make use of therapy and complete research assessments without the need for a translator. Exclusion Criteria: * current/past learning disability, organic brain change, substance dependence (drugs and alcohol) that would compromise the ability to use therapy * current marked risk to self (i.e., self-harm or suicide) that we deem could not be appropriately managed in the Bipolar outpatient clinic at Landspitali. * currently lacking the capacity to give informed consent * currently receiving other psychosocial therapy for depression or bipolar disorder * presence of another area of difficulty that the therapist and client believe should be the primary focus of intervention (for example, Post-Traumatic Stress Disorder, psychosis)