When you think of cortisol, the first thing that comes to mind is its close association with stress, hence its moniker, "the stress hormone." While cortisol may be a close companion when you're rushing for a deadline or running to catch a bus, not many people realize its profound impacts on sleep. If you ever find yourself having difficulty falling asleep and sleeping through the night, there’s a chance your body is too wound up with this stress hormone.
Be that as it may, we need cortisol for our day-to-day functioning. Aside from activating our fight-or-flight response, this hormone is also crucial for waking us up in the morning and lowering body inflammation (when cortisol is present in normal amounts). It’s only when there is an ill-timed, chronic influx of cortisol circulating in your body that it spells trouble for your sleep patterns, as well as your health and wellbeing in the short and long term.
Below, we take an in-depth look at the stress hormone cortisol and how it relates to your sleep-wake cycle. You will discover why your body can produce too much cortisol, how that leads to sleep loss, and vice versa. Last but not least, you will learn how to lower cortisol levels to free yourself from this vicious cycle of surplus cortisol and sleep insufficiency.
Scientifically speaking, cortisol is a glucocorticoid (steroid hormone) produced in the adrenal glands located at the top of your kidneys. The hypothalamo-pituitary-adrenocortical axis (HPA axis) regulates your body's cortisol secretion (we'll talk more about the exact mechanism later).
The primary roles of cortisol include:
We will go into the specifics in the following sections. All you need to know now is that cortisol has its own circadian rhythm. When your cortisol rhythm is properly functioning, your body produces this stress hormone in the right amounts at the right times. This is beneficial and necessary for your overall health. But too much cortisol over prolonged periods triggers a never-ending cycle of elevated cortisol levels and sleep loss that sets you up for various health problems, as you will see.
According to the Natural Medicine Journal, your cortisol levels ebb and flow over a roughly 24-hour period to dictate your sleep-wake cycle. For example, a healthy cortisol rhythm (measured in nanograms per deciliter) for someone sleeping from midnight to 8am would look like this:
As you can see, cortisol is naturally highest in the morning to help you feel alert and beat back sleep inertia before dwindling throughout the day. The rise and fall of this stress hormone is crucial for helping you fall asleep by your target bedtime, stay asleep throughout the night, and wake up in the morning.
In the early morning, your body's cortisol production naturally surges and transitions you into wakefulness. Once you've woken up, this morning cortisol surge continues for 30-45 minutes before returning to its baseline after an hour or so. (The scientific phenomenon known as the cortisol awakening response (CAR) is the combination of this circadian spike in cortisol combined with a postural drive (when you get up after laying flat, or supine, all night, cortisol has an additional spike).)
So, what causes cortisol levels to rise in the morning? In anticipation of wake time, the circadian clock sets off a cascade of hormones that results in the release of cortisol. Past the early morning spike, your body’s cortisol reserves gradually decline as the day goes on. They hit rock bottom typically around midnight. Two to three hours after you’ve fallen asleep, your body starts manufacturing cortisol again until its zenith in the early morning. Then, the cycle repeats itself.
If you’re a night owl, you likely exhibit lower daytime cortisol levels and a later morning cortisol peak compared to early birds. In owls, cortisol often rises just a short time before wake time and in some people, after habitual wake time. The reason being, a later bedtime inevitably delays the fall and eventual rise of the stress hormone from midnight to early morning.
In general, to capitalize on your morning cortisol surge, align your wake-up call with your morning cortisol peak to get the most out of its energizing effects. An erratic sleep schedule, like sleeping past your usual rise time diminishes your cortisol awakening response and incites a “sleep hangover,” so you wake up feeling worse than you normally do.
You can also take advantage of your morning cortisol spike by slotting in a workout session. Because cortisol has anti-inflammatory capabilities, it plays a key role in your body's rest-and-repair mechanism, which may help speed up post-exercise recovery. Getting in a workout will also help with that night’s sleep.
To explain the connection between excess cortisol and sleep loss, let's look at how your stress response system works. You can think of it as a built-in alert system that reacts to any perceived stressor.
The stress response system consists of the autonomic nervous system (ANS) and the HPA axis.
The autonomic nervous system (ANS) is part of your body's nervous system and is made up of:
The ANS works in tandem with the HPA axis to react to external stressors. But, what exactly is the HPA axis?
The HPA axis comprises both the central nervous system and the endocrine system. It consists of the hypothalamus, the pituitary gland, and the adrenal glands. These systems and organs work together to release a calibrated cocktail of brain chemicals and hormones that influence your day-to-night cortisol levels and sleep-wake cycle.
In the presence of a stressor, the fight-or-flight response is activated, as the PNS slides into submission while the SNS and HPA axis take over. Within the ANS, the hormone adrenaline (epinephrine) and the neurotransmitter noradrenaline (norepinephrine, or NE) are released. This is why you feel like you are in a heightened mode of alertness. It also explains some of the physiological reactions you experience, such as a faster heart rate.
At the same time, the HPA axis goes into work mode to bring about the following changes:
As mentioned earlier, the HPA axis interacts with the ANS during times of stress. This interaction is primarily seen in how CRH activates the release of NE during the fight-or-flight response. NE then stimulates the HPA axis to produce more CRF, resulting in a positive feedback loop that amplifies cortisol levels within your body.
Under normal circumstances (short-term states of stress), when there is enough cortisol, this kicks off a negative feedback loop that shuts down the HPA axis's cortisol production. Simultaneously, the PNS reflexively turns on to inhibit the acute stress response. This is essential to lower cortisol concentration back to homeostasis (a state of equilibrium). Unfortunately, a persistent state of stress maintains too-high levels of cortisol that disrupt your cortisol rhythm (see next section).
While your stress response system usually turns off once a threat has passed, never-ending stressors mean your body is stuck in the fight-or-flight mode, resulting in chronic stress. A common example would be a hectic lifestyle overwhelmed with work demands, family obligations, and little downtime.
As you can imagine, the HPA axis activity goes haywire, leading to out-of-whack cortisol production. Instead of the usual peaks and troughs, your cortisol rhythm is now stuck on high cortisol release. While high cortisol levels are great for jumpstarting your day, a cortisol overload throughout the day and too near your bedtime spells doom for your sleep-wake cycle.
High cortisol symptoms aren’t only limited to things like high blood pressure, rapid weight gain, and mood swings. Too much of this stress hormone also threatens your sleep. That's because adrenaline and noradrenaline also appear alongside said stressor, hiking up your heart rate and body temperature. This makes it harder for you to drift off to sleep, much less transition from light sleep to deep sleep.
Hyperactivity of the HPA axis alters your natural sleep architecture in the following ways:
Poor sleep, as a result of too much cortisol, inflates your sleep debt and deflates your next-day energy levels. Predictably, you aren't feeling and functioning at your best. To worsen the issue, there is a cause-and-effect relationship between HPA axis dysfunction and certain sleep disorders. For example, HPA axis hyperactivity may be the cause of insomnia and the byproduct of obstructive sleep apnea.
While excess cortisol incites sleep problems, the resulting sleep loss also intensifies your body's cortisol concentration. Not meeting your sleep need means your body isn't given ample time to curb cortisol secretion, leading to elevated daytime levels of the stress hormone.
A 1997 study by Leproult and colleagues found that just missing a few hours of sleep for one night is enough to hike up your cortisol levels the following evening. The study also notes a lag time of at least an hour in suspending cortisol production. More recently, a scientific review published in June 2021 highlighted that there is ample research indicating a short sleep duration of 5.5 hours or less hiked up cortisol production in the afternoon and evening.
In other words, not only do you feel too wired for sleep, but your target bedtime is also delayed. You are now trapped in a vicious cycle of ever-increasing cortisol and sleep deficiency, which bodes ill for your day-to-day functioning and overall wellbeing.
Still, it’s not just an insufficient amount of sleep that incites cortisol overload. A sleep schedule that’s not aligned with your internal clock can throw your cortisol rhythm off-course, even if you’ve met your sleep need (read: circadian misalignment). A commonplace example of circadian misalignment is social jetlag – a consequence of the discrepancy between an individual’s circadian rhythm and their social clock, and which affects a startling 87% of us). The phenomenon forces a multi hour misalignment every week between your sleep schedule and cortisol pattern.
A recent article published in April 2022 showcases this phenomenon in night shift workers: Based on salivary cortisol samples, female hospital workers have a more muted CAR on the mornings following their night shifts. What’s more, the study highlighted that the muted effect was more pronounced in shift workers who identify as morning chronotypes (aka early birds).
Aside from sleep deprivation and circadian misalignment, other factors like chronic stress and ill-timed exercise also hike up your cortisol levels. For more details, read our recent blog post on what causes high cortisol levels at the wrong times.
As long as there is insufficient sleep, your body remains stranded in the fight-or-flight state, in which your SNS is floored into a perpetual state of overdrive. The strain placed on your body by this persistent force of sympathetic activation leaks out in all manner of health issues, triggering a domino effect of health damage.
First and foremost, you can think of cortisol-induced sleep loss in terms of:
In the short term, acute sleep debt downgrades every aspect of your life that matters, from your cognitive functioning to your immune system to your social relationships.
Over time, acute sleep debt progresses to chronic sleep deprivation, in which a new host of health problems arrive, courtesy of your body’s persistently high cortisol levels. The long-term effects of sleep insufficiency are well-documented in scientific literature, particularly in the form of metabolic health issues such as:
As if the direct impacts of sleep loss itself aren't distressing enough, you also have to contend with the additional health issues that too much cortisol instigates.
While acute cortisol helps fight inflammation, chronic stress subjects your body to consistently high cortisol levels over time. This cortisol dysfunction dials down your immune system response. That's because your body gradually resists cortisol — such that the stress hormone no longer grapples with inflammation but instead triggers it. Consequently, widespread body inflammation sets the stage for countless health issues.
The panoply of health problems from a cortisol overload is, in many ways, similar to those linked to sleep loss due to the incredibly tight connection between excess cortisol and sleep insufficiency. For example, high cortisol levels spur glucose production in the liver and raise blood sugar levels. A 2017 study highlighted that a dysfunctional cortisol rhythm is "associated with insulin resistance and Type 2 diabetes mellitus." In addition, excess cortisol secretion aggravates several cardiovascular risk factors, including high blood pressure and obesity.
In a similar vein, cortisol is known to constrict the blood vessels, which, if at high levels at the wrong time, may negatively affect your heart health. A 2019 study explains this effect is most noticeable following daylight saving time (DST). Just an hour of lost sleep is enough to intensify your risk of heart attacks.
Another health issue associated with unnaturally high cortisol levels is low libido (diminished sex drive). Because the fight-or-flight response redirects blood away from the sex organs, this can lead to erectile dysfunction in men and reduced arousal in women.
An excess of circulating cortisol also cultivates "bad bacteria" to fester throughout your microbiome through the gut-brain connection. This prevents the meaningful absorption of all food nutrients and causes gastrointestinal problems. Matt Walker, the author of Why We Sleep, speculates we will likely discover a two-way relationship where the microbiome communicates and alters sleep through various biological channels, further solidifying the intertwined nature of cortisol and sleep.
While it's easy to lose yourself in the nightmarish labyrinth of cortisol overrun and sleep loss, proper sleep hygiene helps you emerge from the maze by keeping your sleep debt low and your circadian rhythm running smoothly. The reason being, low sleep debt and circadian alignment promote a well-functioning homeostatic process that maintains optimal cortisol levels in your body. With cortisol (and all other key hormones) working optimally, your sleep-wake cycle is steered back on track.
Use our step-by-step Sleep Guide to learn how you can perfect your sleep hygiene.
Just as important for cortisol management is making a conscious effort to minimize your stress levels, as they are the trigger point for chronic cortisol secretion. One effective way to do that is to schedule an evening wind-down routine in the 1-2 hours before bed.
RISE users on iOS 1.202 and above can click here to schedule their nightly evening routine.
Letting go of the day's stressors gives your body a chance to switch from the SNS to the PNS. Remember that the PNS effectively reverses the effects of high cortisol levels during stressful situations to return your body to homeostasis. This switch is key to helping your body move between the two systems without being stuck on high alert all the time. Activating your PNS during your wind-down helps you slide into sleep more effortlessly.
Below, we detail some simple yet effective stress management techniques you can incorporate into your wind-down routine without resorting to sleep supplements:
There is no one-size-fits-all strategy when it comes to managing your stress levels. Experiment with the above cortisol-lowering techniques to see which one(s) work best in helping you sidestep the pitfall of excess cortisol and sleep insufficiency. You may also wish to check out our in-depth guide on how to lower cortisol levels at night.
Now that you understand how cortisol can work for and against you, it's time to turn this stress hormone to your side. A well-functioning cortisol rhythm is essential for helping you sleep and wake at the right times, as well as deal with short-term stressors. The key is not to let your body's cortisol levels get out of hand, or else you risk getting caught in the maelstrom of never-ending cortisol secretion and sleep loss.
Start by reviewing your lifestyle and identifying stressors that are contributing to your chronic stress levels. Next, prioritize good sleep hygiene to keep sleep debt low and your circadian rhythm aligned. Also, don't forget your evening wind-down to tone down your body's stress response.
The RISE app can remind you when you should start winding down, plus when to practice good sleep hygiene techniques from dawn till dusk based on your unique chronobiology. Only when your cortisol rhythm is properly working will you meet your sleep need and have the energy for better days ahead.
RISE users on iOS 1.202 and above can click here to set up any of the app’s 20+ sleep hygiene habits.
Healthy amounts of cortisol at the right times help transition you into wakefulness in the morning and fall asleep by your target bedtime. Ill-timed cortisol production disrupts your sleep-wake cycle so that you have trouble falling asleep and staying asleep, while missing out on the alertness-boosting effect of the cortisol awakening response in the early morning. This leads to a vicious cycle of excess cortisol and sleep loss.
Keep your sleep debt low and work with your body clock through good sleep hygiene practices like well-timed light exposure and exercise. Also, practice healthy stress management techniques and incorporate them into your evening wind-down routine.
A healthy functioning cortisol rhythm is naturally highest in the early morning. But when the cortisol rhythm is steered off course due to triggers like chronic stress, your body is in a constant state of high cortisol production.
The common symptoms of high cortisol levels include weight gain, muscle weakness, a reduced sex drive, high blood pressure, glucose intolerance, depression, and osteopenia. Most importantly, excess cortisol also incites sleep disturbances like insomnia and middle-of-the-night awakenings.
High cortisol levels later in the day and near your bedtime trigger insomnia and other sleep problems. That’s because cortisol is an alertness-boosting hormone. While it’s great for helping you feel awake in the morning and alert throughout the day, too much cortisol circulating in your system too close to bed means you’re too wound up for sleep itself.
The most common causes of a cortisol spike include sleep debt, circadian misalignment, chronically high stress levels, certain medical conditions like kidney disease, and ill-timed exercise.
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