Picture the scene: your to-do list is spiralling and you can't switch off. But you're so severely sleep deprived that you fall asleep as soon as your head hits the pillow... only to then wake up at 3 a.m. on the dot.
This used to be my nightly reality, a nightmarish space where stress, anxiety and middle insomnia punctuated my sleep. As arguably the world's two best and well-known sleep doctors, Dr. Michael Breus and renowned Ted Talk superstar Dr. Matthew Walker, have now explained to me, stress-related cortisol is the main culprit.
Below, I'll explore what cortisol is (spoiler: it's not the enemy of sleep you might think it is), plus I'll share doctor-prescribed tips for lowering stress levels for better sleep.
Key takeaways: At a glance
- We produce cortisol as a stress response to enhance our physical and cognitive abilities. However, cortisol also plays a crucial role in regulating our sleep-wake cycles.
- Cortisol levels rise naturally around 3 a.m. but stress can cause cortisol levels to rise too high or too fast, causing us to wake up in the middle of the night.
- Tips for relieving stress levels, and therefore boosting your chances of sleeping through the night, include spending time in nature and writing a to-do list for the following day.
What is cortisol and what role does it play in sleep?
Cortisol is a hormone commonly associated with stress. Our bodies produce cortisol as a response to stress in order to sharpen our physical and cognitive abilities. However, a response to stress isn’t its only function.
"One of the biggest myths I hear is that cortisol is the enemy of sleep," says Dr. Michael Breus, a double boarded Clinical Psychologist and a Clinical Sleep Specialist.
"It isn't. Cortisol is actually one of the hormones that helps you sleep and wake up at the right times — it should be low while you're sleeping and naturally climb before your alarm goes off."
Cortisol is actually one of the hormones that helps you sleep and wake up at the right times
Dr. Michael Breus, Clinical Psychologist and Clinical Sleep Specialist
"Cortisol is best understood not only as a 'stress hormone' but also as a timing hormone," adds Dr. Matthew Walker, sleep scientist and author of the best-selling book Why We Sleep.
"It follows a strong circadian rhythm: levels fall to their lowest point around the time we fall asleep, begin climbing in the second half of the night, and then surge sharply in the 30 to 45 minutes after we wake — what's called the 'cortisol awakening response'," explains Dr. Walker, a Professor of Neuroscience in the School of Behavioral and Brain Sciences at the University of Texas Dallas.
So the natural rise in cortisol in the early hours of the morning helps us feel alert upon waking. "That rise is not a malfunction," explains Dr. Walker. "It's part of how the body mobilises energy and prepares the brain for the day ahead."
Is cortisol waking me up at 3 a.m.?
If, like me, you're no stranger to 3 a.m. wake-ups, it's not a coincidence. As Dr. Walker explains above, cortisol levels begin to naturally rise around 3 a.m. as part of your Cortisol Awakening Response (CAR).
However, the steady rise in cortisol correlates with the drop off of sleep pressure – our hunger for sleep. As Dr. Walker explains, sleep pressure (or homeostatic sleep drive) has a "chemical signature: adenosine."
Adenosine, a byproduct of physical and mental activity, begins building the moment you wake and begins to drop when you fall asleep.
This means that when cortisol levels begin to rise around 3 a.m., we're more like to wake then than we would at, say, 11 p.m.
That's why the small hours feel so uniquely, maddeningly alert, and why 'just go back to sleep' is useless advice at 3 a.m.
Dr. Matthew Walker, Neuroscientist
A higher than normal baseline level of cortisol, due to chronic stress or anxiety, could mean that when levels rise naturally at 3 a.m., it's enough to wake you up completely.
By then, "the mountain" of adenosine you had accumulated during the day has largely been discharged by sleep.
"You are, in a real sense, running low on the very substance that makes sleep happen," explains Dr. Walker.
"Rising cortisol then tilts an already precarious situation further toward wakefulness. That's why the small hours feel so uniquely, maddeningly alert, and why 'just go back to sleep' is such useless advice at 3 a.m."
Tired but wired
"If you're waking feeling alert, anxious, or with a racing mind, stress-related cortisol may be contributing," says Dr. Shelby Harris, who is board certified in Behavioral Sleep Medicine.
However, all of the experts I spoke to agree that cortisol isn't necessarily the only enemy here. As a woman in her 40s, Dr. Harris points out that hormonal fluctuation could also be to blame for my 3 a.m. wake-ups.
"For women in their 40s and beyond, early-morning awakenings are extremely common during perimenopause and menopause, when fluctuating estrogen and progesterone can make sleep lighter and increase nighttime awakenings," says the author of The Woman's Guide to Overcoming Insomnia.
'The problem occurs when that rise happens too early, too quickly, or in combination with a hyper-alert nervous system'
Dr. Michael Breus
Meanwhile, Dr. Breus, a Diplomate of the American Board of Sleep Medicine, reiterates that rising cortisol levels in the early hours of the morning helps your brain and body prepare for wakefulness.
"The problem occurs when that rise happens too early, too quickly, or in combination with a hyper-alert nervous system, causing your brain to transition from sleep to wakefulness before you're ready," says Dr. Breus, who is also a Fellow of The American Academy of Sleep Medicine.
"That's why recurring 3 a.m. awakenings can be linked to chronic stress, insomnia, sleep apnea, menopause, depression, alcohol, or circadian disruption," continues the sleep specialist. "The key isn't trying to 'lower cortisol' — it's identifying what's causing your stress system and biological clock to become misaligned in the first place."
5 ways to lower stress to combat 3 a.m. wake ups
Cortisol plays a crucial role in regulating our sleep-wake cycle, helping us to sleep deeper earlier in the evening and wake up feeling alert.
While cortisol isn't the enemy to our sleep, stress is — so here's some expert advice on how to lower your stress-related cortisol levels for better overnight sleep.
1. Spend time in nature — but don't feel obliged to walk
We've all been told that exercise, especially in the morning and outdoors, can help promote better sleep. And while that is true, Dr. Walker cites a study that indicates that simply spending time in nature can lower cortisol levels.
However 'spending time in nature' is not exercise by another name, urges Dr. Walker. The sleep scientist flags an additional study that indicates that spending a minimum of twenty minutes either sitting or standing in nature can improve cognitive performance.
"Get into a forest, and don't feel obliged to walk," urges Dr. Walker.
2. Write a boringly specific to-do list for tomorrow
A spiralling to-do list and stress go hand in hand, but writing it down at bedtime could actually help you fall asleep faster.
"Write tomorrow's to-do list at bedtime — and make it boringly specific," says Dr. Walker, who acknowledges that this flies in the face of usual advice.
"In a polysomnography study, participants who spent five minutes writing a to-do list for the coming days fell asleep significantly faster than those who journaled about tasks they had already completed — and the more specific the list, the faster they fell asleep".
3. Take a warm bath
"Take a warm bath — but one to two hours before bed, not right before it," urges Dr. Walker. "Nearly everyone gets the timing wrong, and the timing is the active ingredient"
Three glances at your inbox after dinner may undo more than a lavender bath repairs
Dr. Matthew Walker, Neuroscientist
A 2019 study found that water at 40–42.5°C, for as little as 10 minutes, scheduled one to two hours before bedtime, significantly shortened the time taken to fall asleep and improved sleep efficiency, which is the time it takes you to fall asleep, says Dr. Walker.
Bathing two to three hours before bed gives allows your core body temperature to drop, which is necessary in order to fall asleep.
"Do it five minutes before bed and you get the warming without the cooling, which is the opposite of what you want," says Dr. Walker.
4. Stop working late at night
A small month-long study of IT employees found that checking emails outside of work hours was associated with worse sleep quality, regardless of how long ago they had finished work.
Findings from same study also indicated that those who worked late were more likely to experience a higher cortisol awakening response (CAR), indicating higher stress.
The takeaway? Finish work and don't come back to it. "An evening routine cannot out-run a nervous system that never actually clocked off," says Dr. Walker.
"Three glances at your inbox after dinner may undo more than a lavender bath repairs."
5. Stick to a consistent sleep schedule
In order to optimize your sleep-wake cycle it's important to stick to a regular sleep schedule, such as the 7:1 sleep rule. That's where you go to sleep within the same one hour window every night and accumulate at least seven hours of sleep.
"If you're trying to lower nighttime cortisol, don't waste your money chasing the latest supplement," concludes Dr. Breus, Chief Sleep Officer at Orion.
"The biggest wins come from rebuilding your body's natural rhythm: keep a consistent sleep schedule, exercise regularly, manage stress, and create a bedroom that's cool."
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