The purpose of this study is to determine what dose of a new timed-release tablet of the drug propranolol will reduce secretion of the hormone melatonin in healthy volunteers. This study will also determine whether suppressing melatonin will improve depressive symptoms in people with seasonal affective disorder (SAD). SAD (sometimes referred to as winter depression) is a condition in which people experience depression as a result of seasonal variations in light. Human brains have a circadian pacemaker that regulates many body functions. As the seasons change and light duration varies, the circadian pacemaker regulates seasonal behavior by transmitting a signal of day length to the pineal gland, which secretes the hormone melatonin. Melatonin secretion increases in the winter as the duration of light decreases. Evidence suggests that the melatonin signal of seasonal change is present in people with SAD but not in healthy volunteers; thus there is a possibility that seasonal changes which influence the duration of melatonin secretion control the course of illness in individuals with SAD. This study will determine whether propranolol can shorten the duration of melatonin secretion and mimic the effect of summer days to improve symptoms of depression in people with SAD. Healthy volunteers will be admitted to the hospital for about 2 days. The volunteers will receive either propranolol or placebo (an inactive pill) before going to bed and upon awakening. Blood samples will be collected at various times throughout the study. Participants with SAD will be interviewed periodically on an outpatient basis to determine the onset of depression in the fall or winter. Two weeks after depressive symptoms arise, participants will begin treatment with either propranolol or placebo. At the beginning of the treatment, participants will be hospitalized for about 2 days and will have blood collected at various times. During the hospital stay, participants will continue treatment with either propranolol or placebo in the morning and at night; all participants will receive propranolol at some point during the study. Participants will be interviewed weekly for 4 weeks. Premenopausal women with or without SAD will keep a record of their menstrual cycles and will use a urine test kit to identify the time of ovulation during the month before and after admission to the hospital.
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