Spectral analysis of the sleep EEG of depressed patients before and after total sleep deprivation

Sleep electroencephalography in depressed patients reveals many signs of disrupted sleep, like long sleep latency, frequent awakenings, reduced amounts of time spent in the sleep stages 3 and 4, and early morning wakefulness. Upon total deprivation of sleep for one night, many patients experience an unexpected alleviation of their depression, which usually lasts until the subsequent sleep period. Attempts have been made to explain these changes of mood to result from induced changes in sleep physiological mechanisms. Such attempts can roughly be categorized in two classes. One class of hypotheses concerns proposed disturbances in circadian sleep control (i.e. the timing of sleep is inappropriately controlled), the other class concerns postulated disrupted homeostatic sleep control (i.e. the intensity of sleep is inappropriately controlled). For both types of theoretical approaches data have been published which are consistent with the hypotheses as well as data which are not.