Sleep regulates emotional cognition through the specific mechanism of REM sleep's overnight emotional memory reprocessing — replaying emotionally significant memories from the day in the neurochemical context of REM (low norepinephrine) which enables reactivation and integration of the emotional content without the accompanying physiological stress response, progressively reducing the emotional intensity of aversive memories and facilitating adaptive emotional learning.
Role
The REM sleep emotional regulation mechanism explains one of the most practically significant aspects of sleep health: why well-slept people consistently report that problems feel less overwhelming in the morning than they did the night before — not because the problems have changed but because the amygdala response to them has been modulated by overnight REM processing. The sleep-deprived person, lacking this nightly emotional decompression, approaches each new day with the accumulated unprocessed emotional intensity of the preceding days — producing the characteristic emotional volatility, reduced resilience, and hopelessness of chronic sleep insufficiency that is frequently misidentified as depression when it is, at least partly, a sleep disorder.