Circadian Effects of Escitalopram

Background: The human biological clock (circadian pacemaker) has long been thought to play a role in non-seasonal depression. A connection is suggested by the demonstration of 24-hour rhythms in mood, subjective and objective changes in sleep with depression, and reports of changes in the timing and amplitude of biological rhythms in depression. Furthermore, it is known that the neurotransmitter serotonin has a significant role in regulating biological rhythms and that drugs that act on serotonin (such as some antidepressants) are able to reset the biological clock in animals. Objective: The aim of the study is to obtain preliminary data that will test whether the antidepressant medication escitalopram has a resetting effect on the human biological clock and whether the improvement in depression symptoms with escitalopram correlates with the degree to which the timing of the biological clock is realigned with the timing of sleep. Design: 14-16-week, fixed dose (after titration), open label trial. Setting and Subjects: 50 individuals will be screened for participation. 15 individuals with unipolar, non-seasonal depression will be studied over 1 year. Intervention: Subjects will first complete a one week, single-blind placebo lead-in phase. Subjects will then receive escitalopram for 8 weeks (10 mg/day for the first 2 weeks of treatment and then 20mg/day for the remaining 6 weeks of treatment). Measurements: Subjects will keep a sleep diary and wear a wrist activity monitor throughout the study to document the timing and quality of sleep. On two occasions (end of placebo week and end of last treatment week) blood and/or saliva will be sampled every 30 minutes for 7 hours and the resulting samples will be assayed for melatonin. The onset of melatonin secretion (dim light melatonin onset or DLMO) will be used to mark the timing of the biological clock (circadian phase). Circadian misalignment will be measured using the time interval between the DLMO and the average midsleep of the prior week (phase angle difference or PAD). Mood will be assessed throughout the study using the Hamilton Depression Rating Scale (HAM-D) as well as the Beck Depression Inventory-II (BDI-II) and Beck Anxiety Inventory (BAI).