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Sleep stage transitions and tonic REM in depression
Abstract:
The hypothesis that greater perturbations of EEG-sleep architecture and continuity would occur in clinical depression contingent upon epsilon stage shifts was tested. Duration of successive REM cycles was also evaluated in 16 young adult (17-25 years) nonpsychotic unipolar patients with primary depression and eight age-matched normal controls for 8 hr during 1-3 consecutive EEG recording nights (epsilon N = 55). Two subgroups of eight patients were identified whose polysomnograms contained greater than 100 versus less than 100 epsilon sleep stage transitions. As predicted, sleep was shallow and fragmented to a significantly larger extent in depressives with: greater than 100 stage shifts versus, less than 100 transitions, compared with controls. This was reflected by significantly longer delays in falling asleep, more intermittent wakefulness transitions into stage 1, increased epsilon stage shifts, and more transitional stage 1 sleep. The depressed patients with less than 100 stage shifts (versus greater than 100 transitions relative to the controls) accumulated significantly less total sleep (7.0 vs greater than or equal to 7.6 hr), REM time; exhibited fewer REM episodes, and a slower REM cycle. Compared with controls both patient constituencies accumulated less REM time, showed a propensity for shallow NREM sleep reflected by significantly decreased stage 4, and more frequent transition into stage 1. REM time significantly increased progressively during sleep through the fourth cycle in both controls and depressives. The initial REM cycle was significantly longer among patients (N = 16), and the fourth proved to be shorter compared with controls. The longer first REM cycle in primary depression is construed to represent a disinhibition of neural processes that would normally either attenuate or delay this phenomenon. Accordingly, the possibility is raised that REM sleep disinhibition potentiates the mood disturbances and neurovegetative symptoms of endogenous/primary depression.