When it comes to cortisol and melatonin, the two dominant hormones that regulate stress and sleep, the relationship between them proves to be mutually exclusive. Many, if not all, insomnia sufferers will admit that times of high stress will worsen their inability to fall or stay asleep, and those not sleeping, even for a night or two, will admit it causes them physiologic and psychologic stress. Looking at the release patterns in a 24 hour period of cortisol and melatonin, the reason for this becomes quite obvious. This is why the balance between these two important hormones is referred to as the circadian rhythm, with many medical practitioners focusing on these patterns in not only sleep related disorders, but all health concerns.
Cortisol, sometimes referred to as the “stress hormone”, has a diurnal release pattern, meaning its pattern is repeated within every 24 hour day cycle. Generally, the levels are highest in the morning, peaking within an hour of waking, and slowly decrease throughout the day, reaching its lowest point around bedtime. The high levels in the morning aim to prepare the body for the day, providing energy to allow wake up; and low levels in the evening to allow the body to fall asleep. In addition to sleep-wake cycles, cortisol has actions that contribute to the regulation of blood sugar levels, immune and inflammatory response, and how the body responds to stressors. Problems occur not only when cortisol is too high, but also too low.
Melatonin, commonly referred to as the “sleep hormone”, also has this 24 hour diurnal rhythm, but with the opposite release pattern. It is triggered by light exposure, so it increases with darkness to promote falling asleep, peaking in the middle of the night to keep one sleeping, and declines with light exposure to allow wake up, reaching its minimum midday.
Seeing how these two hormones are released and what affects them, it becomes obvious how easily modern-day stressors can contribute to abnormalities in these patterns, resulting in numerous health concerns. For example, light exposure in the evening has been shown time and time again to reduce nighttime melatonin levels, disrupting the ability to fall asleep appropriately; this effect is even seen with light exposure while sleeping, potentially distributing the ability to stay asleep as well (1). Thankfully, most light exposure disruptions can be somewhat easily mitigated with things such as black out curtains, blue light blockers, and abstaining from electronic use close to bedtime. Other disruptions, such as shift work can be more difficult to work around.
Unfortunately, one of the more difficult contributors of circadian disturbances to mitigate is the influence of stress, whether that be physiological or psychological. Everyone experiences stress in their life, with some managing better than others. Those with stress and sleep problems, tend to have the most trouble. The reason for this lies in how melatonin and cortisol are released in an opposite, yet relatively symbiotic way. Simply put, stress (ie. Cortisol) and an inability to sleep (ie. Melatonin) exacerbate each other. A systematic review and meta-analysis performed in 2024 was able to show consistently that acute sleep deprivation was associated with higher serum cortisol levels (2). This would potentially result in increased inflammation, lowered immune response, and exacerbated insomnia.
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Stress, whether psychological or physiological also causes disruption in sleep. Studies have shown that stress-related sleep disturbances, also known as sleep reactivity, are related to a blunted cortisol response to perceived stress, meaning an abnormality in the release pattern. This blunted cortisol response is therefore a risk factor for the development of insomnia (3).
With this knowledge in mind, it becomes relevant to understand the diurnal patterns of both melatonin and cortisol in patients experiencing any form of sleep disturbance or stress. At AYUMETRIX, we offer a test inclusive of morning, noon, evening, and night levels of both melatonin and cortisol in the Sleep and Stress Panel. The levels are then plotted on a curve and compared to the normal range throughout the 24 hour day. With these results it becomes easier to discern what is influencing the patient throughout the day, leading to confidence in treatment recommendations. For more information, please visit www.ayumetrix.com.
