Clinical Trial of Propranolol for Seasonal Affective Disorder

Overview

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.

Symptoms of seasonal affective disorder (SAD) in humans resemble seasonal changes that occur in animals. Moreover, in both humans and animals, the occurrence of these changes is regulated by light. In animals the circadian pacemaker regulates seasonal behavior by transmitting a signal of daylength to other sites in the organism. This signal is expressed, reciprocally, in the duration of nocturnal melatonin secretion, which is longer in winter and shorter in summer. Sites distal to the pineal that regulate seasonal behavior read and respond to this melatonin signal of change of season. In a longitudinal study, we showed that a homologous melatonin signal of change of season is present in patients with SAD but not in healthy volunteers. In light of the animal models, this finding raises the possibility that seasonal changes in duration of melatonin secretion govern the course of illness in patients with SAD. If so, then an intervention that shortens the duration of melatonin secretion in winter and thereby mimics the effect of summer days should improve symptoms of winter depression. To test this hypothesis, we propose to administer propranolol, a beta-adrenergic receptor blocking medication that is frequently prescribed for the treatment of hypertension, to patients with SAD in the winter. We will administer propranolol at a time of night when it would suppress and shorten the duration of melatonin secretion and then ascertain whether this intervention improves depression. A unique feature of this parallel-design, controlled clinical trial is that propranolol, when administered at a time of day when melatonin is not secreted, can serve as its own active placebo.