As assessed by laboratory studies, sleep abnormalities in those with major depressive disorders can be classified as difficulties initiating and maintaining sleep, abnormal sleep architecture, and disruptions in the timing of rapid eye movement (REM) sleep. Sleep initiation and maintenance difficulties include prolonged sleep latency (sleep onset insomnia), intermittent wakefulness and sleep fragmentation during the night, early morning awakenings with an inability to return to sleep, reduced sleep efficiency, and decreased total sleep time. With regard to sleep architecture, abnormalities have been reported in the amounts and distribution of nonrapid eye movement (NREM) sleep stages across the night. These include increased light, stage 1 sleep and reductions in the amount ofdeep, slow-wave (stages 3 and 4) sleep. REM sleep disturbances in patients with depression include a short latency (65 minutes) to the first REM sleep, a prolonged first REM sleep period, and increased total REM sleep time, particularly in the first one-half of the night (1-3).Sleep disturbances are generally more prevalent among inpatients with depression (80%), whereas only 40% to 60% of outpatients show sleep abnormalities (4). A recent metaanalysis, however, indicated that no single sleep variable reliably distinguished patients with depression from healthy controls Manuscript