A Prospective Investigation of the Natural History of the Long-term Weekly Symptomatic Status of Bipolar II Disorder

Abstract

EWALD HECKER (1898)¹ was one of the first to describe what is now diagnosed as bipolar II disorder (BP-II),² emphasizing its chronic, fluctuating, ambulatory course characterized by depressions with occasional hypomanic periods. Later, Kraepelin³ described hypomanic episodes in the course of manic-depressive illness, and Dunner et al⁴ described a specific course pattern in which hypomanic episodes were interspersed with major depressive episodes (MDEs). Otherwise, descriptions of hypomania are sparse in the literature. They are largely based on cross-sectional studies and focus on duration,⁵ seasonal occurrence,⁶ depressive admixtures,^7,8 or polarity shifts in relation to antidepressant drug therapy.⁹ A variety of descriptions characterizing BP-II have reported both commonalties and differences among BP-II, BP-I, and unipolar major depressive disorders (MDDs).^10-20 Previous studies on the course of BP-II have concentrated primarily on the prevalence and nature of syndromal MDEs and hypomanic episodes. We^21-25 already demonstrated that detailed analysis of the full range of affective symptom severity and polarity presents a more complete picture of the long-term symptomatic structure of mood disorders. We^21-25 found that unipolar disorders and bipolar disorders (BP-I) are both expressed, over time, as dimensional illnesses featuring the full range (spectrum) of affective symptom severity and polarity and that subsyndromal and syndromal affective symptoms fluctuate frequently within the same patient.