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).

Inclusion criteria

• 18-65 years old
• able to comply with requirements of the experimental protocol
• competent to sign informed consent
• have mild to severe major depressive disorder without psychotic features and without a seasonal pattern
• currently be under the care of a licensed mental health care provider or primary care physician
• Score > 7 when interviewed by a trained rater using the 21-Item Hamilton Depression Scale (HAM-D)
• be in good physical health
• not be suicidal
• not be taking any other antidepressant medications besides escitalopram during the study
• be free of antidepressant medications for 2-4 weeks prior to beginning the study
• not have a history of transmeridian travel or shift work in the past 2 months and have no plans for transmeridian travel or shift work for the duration of the study
• be able to maintain a regular sleep wake schedule for the weeks one and nine of study
• women of childbearing potential must have a negative pregnancy test and practice an acceptable method of birth control

Exclusion criteria

• abnormal heart, liver, or kidney function
• significant laboratory abnormalities on Complete Blood Count, Complete Metabolic Set, Thyroid Stimulating Hormone, EKG, & urinalysis
• shift work or transmeridian travel in the last 2 months
• current use of melatonin
• evidence of a primary sleep disorder by history
• women who are pregnant or lactating
• be taking medications with known sedative or stimulating effects or that would interfere with the production of melatonin