Bipolar disorder

Summary

Bipolar disorder is a recurrent chronic disorder characterised by fluctuations in mood state and energy. It affects more than 1% of the world's population irrespective of nationality, ethnic origin, or socioeconomic status. Bipolar disorder is one of the main causes of disability among young people, leading to cognitive and functional impairment and raised mortality, particularly death by suicide. A high prevalence of psychiatric and medical comorbidities is typical in affected individuals. Accurate diagnosis of bipolar disorder is difficult in clinical practice because onset is most commonly a depressive episode and looks similar to unipolar depression. Moreover, there are currently no valid biomarkers for the disorder. Therefore, the role of clinical assessment remains key. Detection of hypomanic periods and longitudinal assessment are crucial to differentiate bipolar disorder from other conditions. Current knowledge of the evolving pharmacological and psychological strategies in bipolar disorder is of utmost importance.

Introduction

Fluctuations in mood are common in life, particularly when faced by stressful events. Nevertheless, when mood swings are striking and persistent, and result in notable distress or impairment, there could be an underlying affective disorder. Affective disorders can be classified along a spectrum defined by the extent and severity of mood elevation, from unipolar to bipolar II to bipolar I.¹ Individuals with unipolar disorder present with depressive episodes only, and those with bipolar II or I disorder show increasingly pronounced episodes of mood elevation.

Bipolar disorder affects more than 1% of the world's population irrespective of nationality, ethnic origin, or socioeconomic status and represents one of the leading causes of disability among young people.² In a worldwide mental health survey,³ the prevalence of bipolar disorders was consistent across diverse cultures and ethnic groups, with an aggregate lifetime prevalence of 0·6% for bipolar I disorder, 0·4% for bipolar II disorder, 1·4% for subthreshold bipolar disorder, and 2·4% for the bipolar disorder spectrum. Access for patients to mental health systems, however, differs substantially across countries, making management of this disorder especially difficult in low-income countries.³ With respect to sex, bipolar I disorder affects men and women equally whereas bipolar II disorder is most common in women.⁴

Bipolar disorder is a lifelong episodic illness with a variable course that can often result in functional and cognitive impairment and a reduction in quality of life.5, 6 In WHO's World Mental Health surveys,² bipolar disorder was ranked as the illness with the second greatest effect on days out of role. Because bipolar disorder is mainly diagnosed in young adulthood, it affects the economically active population and, therefore, connotes high costs to society.⁷ The onset of mania in later life might be indicative of an underlying medical comorbidity.⁸ Because of the recurrence and chronicity of bipolar disorder, not only is acute treatment for management of mood episodes fundamental but also pharmacological and psychological approaches for prevention of further episodes are important.

In this Seminar, we discuss topics in bipolar disorder including clinical presentation, diagnostic classification systems, current knowledge about causes, prognosis across the lifespan, and pharmacological and psychological treatments. Furthermore, we include issues of particular interest, such as management of bipolar disorder in pregnancy and adolescence and monitoring. Finally, we address emerging trends in diagnosis and treatment and future developments.