Individual variations in the sleep of depression.

Variations in the intensity or severity of affective disorders were evaluated relative to perturbations in nocturnal sleep physiology. Individual variations in polygraphic features of the sleep cycle based upon psychopathologic scale ratings were investigated in two constituencies (Ns = 6) for 8 hr during 1-3 consecutive nights. The constituencies consisted of twelve young adult (18-25 years) nonpsychotic unipolar depressed psychiatric patients with a primary affective illness and an age-matched normal healthy control group (N = 8). The severely versus mildly depressed patient subgroups scored significantly higher on the Hamilton, Beck and Zung psychopathologic rating scales, indicating a larger magnitude of depressive symptomatology. The average value for total time asleep was 6.1 hr in severely versus 7.8 hr among the mildly depressed patients and controls. EEG-sleep of the severely versus mildly depressed patients and controls contained significantly less stages 2 and 3. Although total time asleep was almost identical in the mildly depressed constituency compared with controls, patients accumulated significantly more of stages 2 and 3. Both patient subgroups exhibited a significantly shorter REM latency than controls. REM latency was reduced to a significantly lower level in the severely versus mildly depressed patients. A significant decrease of REM cycle duration occurred in the polygraphic sleep recordings of severely depressed patients compared with the age-matched controls. The shortened REM latencies indicate a disinhibition of neural processes that would normally delay appearance of the initial REM episodes during nocturnal sleep. The present study generally extends and confirms finding on nocturnal EEG-sleep disturbances in depression associated with the severity of affective illness, particularly the disrupted REM cycle and shorter REM latency.