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Combining a lightweight telemetric mobility sensing system with nightly EEG-sleep recordings, the authors obtained continuous monitoring of rest-activity cycles among psychiatric patients hospitalized for primary depression or acute schizophreniform thought disorder. The patients with primary depression had a significantly higher percentage of their total 24-hour motor activity distributed during the night. Furthermore, this increased nocturnal motor activity did not correlate significantly with concurrent EEG-sleep measures of wakefulness. Indeed, the best predictors of wakefulness were measures of daytime activity. This desynchronization of sleep and nighttime motor activity in primary depression may explain the need for combined pharmacotherapy in some severely depressed patients. The authors suggest that expressing activity as a percentage distribution function, rather than in terms of absolute amplitude, provides an objective diagnostic index of depression.
Foster et al. (Mon,) studied this question.