A disruption in the normal patterns of sleep is one of the main characteristics of major depression. How are normal sleep patterns disrupted? The amount of time spent in nondreaming, deeply relaxed sleep doubles or triples during major depression. Depressed people often awaken spontaneously at three or four o'clock in the morning and cannot get back to sleep even though they are still tired. The majority of depressed people sleep excessively, usually for 18 to 20 hours a day, day after day. Periods of dreaming REM sleep occur in regular 90-minute cycles rather than the normal sporadic and variable periods of REM.