Diagnostic Criteria and Epidemiology of Bipolar Disorders

Bipolar disorder (BD) is a spectrum of potentially serious mental health conditions characterized by distinct periods of extreme moods (including both depression and mania). BD is a significant public health challenge, as the diagnosis is associated with profound impacts on functioning, quality of life, health expenditure, and mortality. The onset of mood symptoms typically occurs in adolescence and early adulthood, meaning such impacts have the potential to be present across the lifespan. Accurate and timely diagnosis is essential to facilitate the provision of appropriate interventions, including psychological therapies. However, in practice, significant delays between the onset of mood symptoms and BD diagnosis have been noted, which can negatively impact prognosis. This chapter outlines the diagnostic criteria for mood episodes and conditions on the BD spectrum according to both major diagnostic manuals. Key aspects of the epidemiology and course of BD are reviewed. Given the unfortunately common and problematic issue of missed or misdiagnosis of individuals with BD, a number of strategies to enhance the accuracy of BD diagnosis are presented, including careful consideration of comorbidities and differential diagnoses, use of screening instruments and structured diagnostic interviews, and ongoing assessment of mood as part of measurement-based care. Finally, the broader impacts of BD on functioning, quality of life, and physical health are outlined to facilitate person-centered case conceptualization, treatment planning, and monitoring of the impacts of psychological interventions across the breadth of treatment outcomes valued by individuals diagnosed with BD.