Bipolar disorder is a common mental disease that imposes a very high societal burden in terms of morbidity, mortality, lost productivity, and costs. The 1-year prevalence of bipolar disorder is 1–2%. Mean age at onset is in the early to mid-twenties, and the risk of recurrence of episodes after a first manic episode is high. Most patients start with unipolar depressive episodes, and among these, approximately 1% of patients convert from depressive disorder to bipolar disorder per year. Comorbidity with anxiety disorders, alcohol and drug dependence, and personality disorders is high. Bipolar disorder is associated with long-term deficits in social, functional, and cognitive outcomes, and life expectancy is decreased approximately 10 years, emphasizing the need for future studies on early intervention.