The dark side of bipolarity: detecting bipolar depression in its pleomorphic expressions

The depressive expressions of bipolar disorders have long been neglected. Current data, from both clinical and epidemiologic studies, indicate that such expressions far exceed the manic forms in both cross-section and during follow-up course. Thus, mania occurs in 1% of the population at large; bipolar depression afflicts at least 5 times more people. Much of the new literature on this subject has emphasized its high prevalence, morbidity, and mortality. There has been relatively less attention paid to the phenomenology of bipolar depression as it presents clinically. This special issue (volume 84/2-3, 2005) is devoted to a systematic data-based in-depth examination of the different clinical expressions of bipolar depression including, among others, retarded depression, agitated and/or activated depression, mood-labile depression, irritable-hostile depression, atypical depression, anxious depression, depressive mixed state, and resistant depression. Both bipolar I (BP-I), and the more prevalent yet relatively understudied bipolar II (BP-II), are covered. We trust that this extensive coverage of the "darker" side of bipolarity will set the stage for a much needed renaissance in its complex phenotypic expressions-and its delimitation from unipolar depression (UP). The phenomenology of BP-I depression ranges from depressive stupor to agitated psychosis, whereas UP depression expresses itself in psychic anxiety, and insomnia, as well as retardation. BP-II compared with UP is more likely to have atypical features, mood lability, hostility, activation, biographical instability, multiple anxiety comorbidities, suicidal tendencies, and to be rated as less "objectively" depressed. These findings are complex and do not fully agree with the conventional characterization of BP as retarded and UP as anxious and agitated. The inconsistency between the conventional and the phenomenology described herein is largely due to depressive mixed states, which tend to destabilize BP-II, and may account for the "contradictory" relationships of affect, sleep, drive, and psychomotor activity in mood disorders.