Sleep laboratory adaptation in normal subjects and depressed patients ("first night effect").

Abstract The sleep EEG patterns of 21 depressed patients and 15 control subjects are reported in terms of the changes from night 1 to night 2 in the sleep laboratory. On night 2 there were several significant changes for the control subjects: (i) a decrease in the time spent in “awake” and “drowsy”; (ii) an increase in time spent in stage 3; and (iii) a reduction in the latency to the first REM period and first stage 3. There was an increase in the number of rapid eye movement periods on the second night, which was just short of statistical significance. The changes manifested by the depressed patients were in the same direction, though they were less marked than in the controls. The findings support the concept of an increased state of vigilance or arousal on the first laboratory night. They also indicate a frequent tendency to miss the first REM period on the first study night.