Correcting Circadian Rhythms to Breakthrough in Bipolar Disorder

The purpose of this study is to test whether a dietary supplement (low-dose melatonin) commonly used to treat night owls, administered in conjunction with a behavioral sleep intervention, will help to shift the brain clock earlier and improve mood and sleep in bipolar disorder. Eligible participants will be randomized to receive melatonin plus a behavioral sleep intervention or placebo plus a behavioral sleep placebo. The hypotheses for this study include: * Melatonin plus behavioral sleep intervention (compared to placebo plus behavioral sleep placebo) will produce a greater advance of dim light melatonin onset (DLMO), between pre- and post-treatment. * Melatonin (compared to placebo) will produce a greater reduction in Patient Health Questionnaire-9 score between pre- and post-treatment.