Sleep helps properly regulate both the HPA and the SAM axes. During sleep, levels of cortisol, adrenaline, and noradrenaline drop. As a result, lack of sleep is associated with increased levels of stress hormones and increased stress reactivity. As you know from Chapters 5 and 6, these stress hormones kick off the party, triggering brain, hormone, immune, and epigenetic responses to stress. The downstream effects are impaired cognitive function, memory, and mood regulation. Sleep deprivation doesn’t just make you groggy and cranky; it also makes you sick. Lack of sleep is associated with
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