Sleep and circadian rhythm abnormalities in the pathophysiology of bipolar disorder

Among other factors, bipolar disorder is characterized by disturbances in sleep and biological rhythms that typically cycle over a 24-h, or circadian period. Indeed, almost all of the functions that constitute symptoms of depression and mania (changes in mood, energy, sleep, interest, appetite, capacity for concentration, etc.) show relatively regular variation over the circadian period. Thus, it would appear logical to search for clues to the pathophysiology of bipolar disorder in the function of the circadian timing system (Wirz-Justice in Int Clin Psychopharmacol 21:S11-S15, 2006). In this chapter, we review the known sleep and biological rhythm abnormalities associated with bipolar disorder. We describe the nature of these circadian rhythm abnormalities and review the evidence supporting their role in bipolar episodes. Last, we discuss a number of pharmacologic and psychosocial treatments for bipolar disorder that target sleep and biological rhythm abnormalities, and we examine their effect on bipolar episodes and symptoms.