|January 18, 2024

Caffeine and Cortisol: Does Coffee Stress You Out?

By Bulletproof Staff
Reviewed for Scientific Accuracy

Caffeine and Cortisol: Does Coffee Stress You Out?

More than 2 billion people enjoy a cup of coffee every morning, including 85% of the U.S. population [1,2].

I also want to answer a few common questions about coffee. This article will touch on caffeine tolerance and coffee-related cortisol release. Enjoy!


Will you build a tolerance to caffeine if you drink coffee every day?

It depends. Caffeine affects different people very differently, partly because your genetics influence your response to caffeine. That’s why a cup of coffee that barely wakes you up may keep your friend from sleeping for two days.

That said, the basic mechanism behind caffeine is the same for everyone. Your brain uses a neurotransmitter called adenosine to tell you that you’re tired; the more adenosine you build up, the more tired you feel. When you take caffeine it prevents adenosine from acting on your brain, making you feel more alert.

Here’s the good news: for most people, tolerance to caffeine only applies to its effects on heart rate, blood pressure, and negative side effects (jitteriness, for example). Odds are you won’t build a tolerance to coffee’s alertness and wakefulness effects [3].

However, there is a different type of tolerance to consider. Ready for some cool neuroscience?

Your brain is good at keeping the status quo and it doesn’t like change. If you take a drug habitually, your brain learns when the drug is coming and gets ready to combat its effects.

For example, if you drink coffee every morning, your brain picks up cues (the smell of the coffee, the act of putting grounds in the French press, etc.) that it associates with incoming caffeine. As soon as you get out your French press, your brain will start making you more tired, less alert, etc. to preemptively cancel out the boost the caffeine will give you. The result: you feel the coffee less – and if you smell someone else’s coffee but don’t drink it, you’ll get sleepy, and without the hit of caffeine to follow you’ll stay sleepy. This phenomenon happens with alcohol [4], painkillers [5], and possibly coffee [6,7].

There’s a hack for cue-based tolerance. You just have to break your brain’s association between coffee and caffeine. You can try:

  • Not drinking coffee every day (but who wants to give up daily coffee?)
  • Adding a cup of decaf in the afternoon – half the time you get caffeine, half the time you get decaf, and your brain will stop associating coffee with caffeine. It will also stop associating caffeine with mornings, which could make waking up much easier for you.
  • Switching up where you drink your coffee. Your brain notices where you are when you take a psychoactive substance, but it will have a harder time forming an association if you keep changing places on it. So if you usually enjoy your cup of joe in the kitchen, start taking it to your desk with you now and then. Better yet, go for a walk with your coffee a couple times a week.

If you keep your brain guessing you just might feel your morning cup a little more.


Does coffee trigger cortisol release?

Cortisol is the infamous hormone you release when you’re stressed. In high doses it inhibits brain function, slows metabolism, breaks down muscle, and increases blood pressure. Have you ever felt panicked before a public speech and forgotten everything you were going to say? That’s what a big bump in cortisol feels like. And if you’re looking for stress relief, lowering cortisol helps.

Cortisol isn’t all bad, though. In fact, it’s necessary for you to function. Cortisol peaks in the morning, helping to wake you up, and it can be a useful as an indicator of strain, letting you know when to slow down or stop something that’s stressing you out. Cortisol also decreases inflammation – that’s part of the reason your body releases it in response to, for example, a workout that tears your muscle tissue.

Low cortisol is an issue, too. Insufficient cortisol can leave you feeling tired, emotional, and anxious. As long as you avoid chronically elevated or depleted cortisol you can make the little hormone work to your advantage.

A common argument against drinking coffee is that it triggers cortisol release, but (forgive me for getting nitpicky) that may not be true. Caffeine (not coffee) definitely triggers cortisol release [8]. In fact, the increase in cortisol part of the reason caffeine makes you feel more alert.

Remember a few paragraphs ago, when I was talking about how you build a tolerance to some of caffeine’s effects but not others? Cortisol release is one of the effects to which you build tolerance. If you only take caffeine now and then, it causes a big boost in cortisol. But if you get caffeine daily (by drinking coffee every morning, for example) your body tempers the cortisol response [8]. You still release cortisol, but not enough to worry about unless your cortisol is already out of whack.

Does coffee itself (separate from caffeine) cause cortisol release? Mycotoxins do, at least in mice [9,10], and they cause inflammation (a common trigger of cortisol release) in humans. It’s difficult to say whether mold-free coffee increases cortisol.

Regardless, studies suggest that cortisol release from caffeine is mild if you drink it daily. For most of us, that little bump shouldn’t be a problem.


That’s it for today. Thanks for reading!