young man studying at night, stressed, caffeine

Sleep Series – Part 5: 6 Factors that Increase Evening Cortisol Levels

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Time for another installment in the Sleep Series! We already learned about high-quality sleep and why days are supposed to be bright, while nights should be dark. The last post introduced the stress hormone cortisol, and its effect on sleep. In an ideal situation, cortisol is naturally high in the morning and tapers off throughout the day to low levels in the evening resulting in high-quality sleep.

In modernity, stressors don’t stop just because it’s night time (though I suppose we don’t worry about nocturnal predators anymore). Evening cortisol levels can be elevated for a number of reasons. I don’t want anyone stressing about stress, so let’s have a good look at some sources of stress to become aware of some common causes of elevated evening cortisol levels.

The next post will focus on solutions! It will be about ways to bring down evening cortisol levels when situations are not ideal. That way, we’ll have some stress-busting strategies in our collective toolbox so we can all sleep better. First, let’s look at why evening cortisol levels can be high in the first place.

Factors that Increase Evening Cortisol Levels:

This section might appear a little pessimistic as some of these factors are hard to avoid, but again, the key point of this section is to become aware of stress so we can actively know how to manage it most effectively. This is not a completely exhaustive list, but a really good start. So, here are the stressors I find commonly responsible for increasing evening cortisol and lowering sleep quality:

1. Sleep deprivation from the previous night/nights

Losing sleep one night will cause higher cortisol levels the next day and into the evening. This often begins a vicious cycle. Skipping out on a good night’s sleep is a stressor in and of itself, and the increased stress will lead to impaired sleep the next night. Honestly, this is an annoying feature of the human body that is somewhat inescapable. This is why it usually takes more than one night to recover from a night of next-to-no sleep.

My thoughts on this are that the human body may have adapted to sleep deprivation with additional stress since there must have been a good reason that you were kept awake last night. That is, there must have been some threat keeping you up. Before there were Netflix marathons and endless nightlife options keeping us awake, only life-threatening circumstances (hostile humans and predators) would have kept us up during dark nights. Today, our stress response is the same no matter what kept us up. Come on body, adapt already!

2. Stressful thoughts, anxiety, and negative moods

I can relate to this one. Anxiety in general has cost me many good nights’ sleep. This isn’t always easy to control, but the science is clear: negative thoughts that lead to anxiety and bad moods increase cortisol, and if that’s happening right before sleep, well, you can figure out what happens. The study quoted shows variability in this effect between individuals, however. Some of us get stressed over certain thoughts more than others. Again, awareness is key – if you know that talking about a stressful work project gets you amped up, then don’t talk about it before bed. If an awkward conversation with a friend or family member has to happen, late at night is the worst time (unless its unavoidable). Tackle that as early in the day as you can. An exception would be when you need to get something off your chest to de-stress. Do what you gotta do. Just try not to get too worked up before bed if you can help it.

Even anxiety surrounding the anticipation of an earlier than usual waking time can alter sleep patterns. Subjects in this study were told after several nights of waking up when they wanted that they’d be awakened several hours earlier the next morning. They showed an increase in a stress hormone precursor (a hormone that stimulates stress hormone secretion) an hour before their anticipated earlier-than-usual wake time. This happened while they were sleeping. Our thoughts affect our sleep! Depending on the situation, this is not necessarily a bad thing (don’t want to miss your flight, after all), but it is something to be aware of.

3. A very noisy environment

It’s tough to truly relax when your environment is irritatingly noisy isn’t it? Science agrees. Exposure to a noisy environment raises cortisol levels. In that specific study, workers who were exposed to loud industrial noise all day didn’t experience the normal circadian reduction in cortisol as the day progressed, and were pretty cranky after work (and probably tough to deal with at home). Wearing earplugs solved the issue. Other studies have shown individual variability. Specifically, men have been reported to be more sensitive to noise than women.

Again, I have learned this personally. Being out in a loud environment (party, concert, evening jam sessions with drums and amps) until late in the evening does not make it easy to fall asleep, and even if I do, I’m not at my best the next day. Earplugs have helped, but I still feel like my brain gets rattled! Sometimes I just accept this, and other times I get out of the noise early so I can sleep better. Camping out in the quiet woods certainly is calming, isn’t it?

4. Prolonged intense exercise in the evening

I play ultimate frisbee, and have for years. It’s a blast. During university, the intramural league sometimes scheduled games at 10 pm, which were over by 11:30 or so. At first I figured it would be no big deal as I was normally hitting the sack around midnight during that time anyway. The first time I did it, I went home sweaty and pumped up at 11:45, and could not sleep for the life of me until 2:30 am. I just laid there, wide awake, tossing and turning, heart-beating hard until the effect wore off and I finally got to sleep. Needless to say, the next day was a struggle. I hear similar reports from my late-night hockey-playing friends.

Prolonged intense exercise produces cortisol. In the study quoted above, the subjects who kept up 76%+ of their max intensity for more than 59 minutes had significant increases in cortisol that stayed high even after 20 minutes of recovery. Late night exercise enthusiasts: worry not! Lower intensity exercise (walking and the like) did not produce cortisol. You don’t have to be a couch potato. And if you’re going to do something intense, keep it short (well under an hour), and there won’t be a noticeable increase in cortisol.

5. Caffeine consumption

This one is no surprise to most people. Caffeine consumption raises cortisol levels, especially when combined with stressful mental or physical tasks. In the morning and throughout your workday, this can be a good thing. You’ll be on point, if perhaps a little jittery. In the evening however, there’s a good chance it’ll keep your cortisol high into the night and lower the quality of your sleep.

Truth be told: I consume moderate amounts of caffeine (1-2 cups of coffee, a cup of tea) almost every day and quite enjoy it and sleep great, but I keep it to the morning and early afternoon. If I drink it later on, my sleep definitely suffers. That being said, sensitivity to caffeine is highly variable, and some people report no problems at all. Self-awareness goes a long way.

6. Severe Prolonged Caloric Deficits (chronic undereating)

A healthy human undereating a little here and there won’t result in any harm, but a prolonged highly-restrictive caloric deficit results in elevated cortisol levels. If you have some weight to lose, prolonged crash dieting will result in a huge stress on your system. It’s better to take a longer-term view of weight loss so that cortisol levels won’t blast into the sky. A little bit at a time is much more sustainable, and won’t result in much stress.

I personally notice that if I’m not eating enough when I’m training hard, I start to get urges to snap at people. That’s when I know it’s time to seriously chow-down so my body can relax and recover. Sometimes overtraining is really just undereating.


Some of these factors are highly controllable (caffeine, prolonged caloric deficits, intense evening exercise), while others are not. My goal with this post was to raise awareness of what could cause higher evening cortisol levels so that readers will have a better understanding of why their sleep suffers in some situations.

That being said, even in situations where there is little control over some of these factors, there are ways to bring down evening cortisol levels so that even the most stressed-out, worrying, dieting, workaholic insomniac can get healthy, restful sleep.

And that will be the focus of the next post! Stay tuned!

Readers: What are your experience with these factors? Any more worthy of mentioning?

– G

6 thoughts on “Sleep Series – Part 5: 6 Factors that Increase Evening Cortisol Levels”

    1. Hi Sue! Thanks for the commment.

      That’s quite interesting, and to be honest, I’m not sure. How was your cortisol tested? In general, if you feel ok and are in good health, it might not be anything to be concerned about. That said, high cortisol when sleeping is a concern. Maybe it goes down before you sleep? At what time is it still high? I’m not a doctor, so a physician might be more appropriate to talk to about this.

      Thanks again,


  1. This is one of the most informative articles I’ve found on the net. I know I’ve commented on another part of this series but just wanted to say again, thank you sooo much. It’s really helped me understand what’s happening with my sleep!

  2. Hi,
    I just wanted to share that I need more sleep than I get when I am at work. The minute I have a break, body fat melts away! I am also focused on keeping caffeine to a minimum and only in the morning. Many thanks for these articles! Nico.

    1. Nico,

      I can definitely relate! Even knowing that I have to be up at 5:30 am can make me anxious enough to cut into my sleep quality. A consequence of modern scheduling.

      I just checked out your site. Excellent work. I love the emphasis on training intensity as opposed to merely volume. Coincidentally, next week’s post focuses on exactly that.

      Thank you very much for leaving a comment!


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