Two key hormones, cortisol and melatonin, orchestrate the connection between stress and sleep and significantly influence your sleep quality. These hormonal players typically collaborate seamlessly during your sleep cycle, with melatonin surging at night to make you feel sleepy and cortisol peaking in the early morning to wake you up from sleep.
However, when stress lingers into the night, the brain triggers a release of cortisol, keeping your body in a heightened state of alertness as part of the fight-or-flight response. Cortisol and melatonin maintain an inverse relationship; when cortisol levels rise, melatonin levels decline, and vice versa. Essentially, stress-induced cortisol suppresses melatonin, resulting in a challenging path to sleep. Elevated cortisol levels hinder the onset of sleep and disrupt the continuity of sleep, impeding your ability to reach the restorative depths of deep sleep and REM sleep.
According to the National Institute of Health, research has shown that individuals with insomnia tend to show higher nocturnal cortisol levels.
Furthermore, the brain relies on serotonin to synthesise melatonin. Prolonged exposure to chronic stress often leads to reduced serotonin levels, which diminish melatonin production and increase sleep disturbances.
As the day wears on, stress's impact on your sleep becomes more profound. For instance, you might find yourself lying in bed, preoccupied with work-related responsibilities or financial concerns, making it a Herculean task to initiate and sustain sleep. The cyclic effect of stress-induced sleep problems can fuel even more stress, creating a relentless feedback loop. Fatigue can trigger further stress, upsetting the delicate balance of hormones crucial for sleep.
The brain's ability to form associations compounds the problem, as it becomes progressively more challenging to retire to bed each night when your brain recognises it as a place of anxious experiences.
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