Answers are grounded in this paper and cite their sources.
Systematic variation in aspects of the sleep-wakefulness cycle of a depressed woman showed that recovery occurred reliably after 19 to 20 hours sustained wakefulness, unrelated to diurnal rhythm. Depression returned during as little as 15 minutes sleep. The effect of sleep deprivation was a specific response, probably unrelated to REM sleep.
No takes yet. Share an insight, caveat, or question.
Knowles et al. (1979) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: