1. Introduction
Although mania and hypomania are the signature and most recognizable characteristics of bipolar disorder, depression is its most frequent clinical presentation. This is dramatically demon
strated in a long-term follow-up of 146 patients with bipolar I disorder, which found that nearly half of the time over 13 years patients were symptomatic in some fashion, overwhelmingly with depressive symptoms (Judd et al., 2002). Thus, nearly 40% of the time over 13 years, individuals with bipolar disorder were depressed. In contrast, patients were manic or hypomanic less than 10% of the time and without symptoms about half the time (Judd et al., 2002). The predominance of depressive compared with mood elevation symptoms was even greater when considering patients with bipolar II disorder (Judd et al., 2003).