Chronic stress disrupts sleep through the dysregulation of the Hypothalamic-Pituitary-Adrenal (HPA) axis. When you experience prolonged stress, this system remains hyperactive, leading to elevated levels of cortisol throughout the night. Cortisol is a primary stress hormone that acts as an antagonist to melatonin, the hormone responsible for signaling the body to sleep.
High nocturnal cortisol levels increase physiological arousal, keeping your heart rate and core body temperature higher than ideal for deep sleep. This state of hyperarousal prevents the brain from transitioning effectively into Stage 3 Non-REM sleep, which is the deep, restorative stage essential for physical repair and cognitive recovery.
Furthermore, chronic stress can suppress the production of adenosine, a chemical in the brain that builds up during the day to create sleep pressure. Without sufficient adenosine buildup and with the constant presence of fight or flight hormones like adrenaline and norepinephrine, the brain remains in a state of vigilant alertness. This neurological state prioritizes survival mechanisms over restorative biological processes, leaving you feeling unrefreshed even if you manage to fall asleep.
