How does sleep affect mood?
Sleep loss reduces positive emotion, amplifies negative emotion, and impairs emotional regulation. Even one night of partial sleep deprivation measurably worsens mood the next day.
Lab evidence
Studies on partial sleep restriction (4–5 hours per night) consistently show next-day decreases in positive mood scales (PANAS) and increases in irritability and anger ratings.
The amygdala mechanism
Walker (2017) summarizes brain-imaging research showing the amygdala (threat-detection center) becomes more reactive after sleep loss while the prefrontal cortex (emotional regulation) becomes less responsive. The result: stronger emotions, weaker control.
Recovery
One or two nights of full recovery sleep typically restores mood baseline. Chronic short sleep prevents that recovery and compounds the effect.
Sources
- Matthew Walker, Why We Sleep (Scribner, 2017). Why We Sleep: Unlocking the Power of Sleep and Dreams
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