Not only is bipolar disorder a chronic, severe psychiatric disorder, it is also expensive to treat and expensive to society. An estimate of the total cost of bipolar disorder made more than a decade ago was as high as 45 billion dollars per year. Most of this cost is accounted for by indirect costs related to reduced functional capacity and lost work. Patients with bipolar disorder have higher rates of utilization of healthcare resources compared with the general population and compared with patients with other types of psychiatric conditions. Comorbidity contributes to the heavy burden that bipolar disorder imposes on society. Bipolar disorder frequently occurs together with other psychiatric disorders, especially anxiety disorders and substance abuse. In addition, bipolar disorder has been associated with a variety of general medical conditions, which further complicate management of the psychiatric disorder.