What Caffeine Actually Does To Your Brain

What Caffeine Actually Does To Your Brain

For all of its wild popularity, caffeine is one seriously misunderstood substance. It’s not a simple upper, and it works differently on different people with different tolerances — even in different menstrual cycles. But you can make it work better for you.

Photo by rbrwr.

We’ve covered all kinds of caffeine “hacks” here at Lifehacker, from taking “caffeine naps” to getting “optimally wired”. But when it comes to why so many of us love our coffee, tea or soft-drink fixes, and what they actually do to our busy brains, we’ve never really dug in.

Buzz: The Science and Lore of Alcohol and Caffeine

What follows is a brief explainer on how caffeine affects productivity, drawn from Buzz and other sources noted at bottom. We also sent Braun a few of the questions that arose while reading, and he graciously agreed to answer them.

Caffeine Doesn’t Actually Get You Wired

Right off the bat, it’s worth stating again: the human brain and caffeine are nowhere near totally understood and easily explained by modern science. That said, there is a general consensus on how a compound found all over nature, caffeine, affects the mind.




It’s an apt metaphor, because it spells out that caffeine very clearly doesn’t press the “gas” on your brain, and that it only blocks a “primary” brake. There are other compounds and receptors that have an effect on what your energy levels feel like — GABA, for example — but caffeine is crude way of preventing your brain from bringing things to a halt. “You can,” Braun writes, “get wired only to the extent that your natural excitatory neurotransmitters support it.” In other words, you can’t use caffeine to completely wipe out an entire week’s worth of very late nights of studying, but you can use it to make yourself feel less bogged down by sleepy feelings in the morning.

These effects will vary, in length and strength of effect, from person to person, depending on genetics, other physiology factors, and tolerance. But more on that in a bit. What’s important to take away is that caffeine is not as simple in effect as a direct stimulant, such as amphetamines or cocaine; its effect on your alertness is far more subtle.

It Boosts Your Speed, But Not Your Skill — Depending On Your Skill Set

The general consensus on caffeine studies shows that it can enhance work output, but mainly in certain types of work. For tired people who are doing work that’s relatively straightforward, that doesn’t require lots of subtle or abstract thinking, coffee has been shown to help increase output and quality. Caffeine has also been seen to improve memory creation and retention when it comes to “declarative memory”, the kind students use to remember lists or answers to exam questions.

(In a semi-crazy side note we couldn’t resist, researchers have implied this memory boost may be tied to caffeine’s effect on adrenaline production. You have, presumably, sharper memories of terrifying or exhilarating moments in life, due in part to your body’s fight-or-flight juice. Everyone has their “Where I was when I heard that X died” story, plugging in John F. Kennedy, John Lennon or Kurt Cobain, depending on generational relatability).

Then again, one study in which subjects proofread text showed that a measurable boost was mainly seen by those who could be considered “impulsive” or willing to sacrifice accuracy and quality for speed. And the effect was only seen in morning tests, indicating the subjects may have either become lightly dependent on caffeine, or were more disposed to such tasks at that time of day.

So when it comes to caffeine’s effects on your work, think speed, not power. Or consider it an unresolved question. If we’re only part of the way to understanding how caffeine effects the brain, we’re a long way to knowing exactly what kind of chemicals or processes are affected when, say, one writes a post about caffeine science one highly caffeinated afternoon.

For a more direct look at what happens to your brain when there’s caffeine in your system, we turn to the the crew at Current. They hooked up one of their reporters to a brain monitor while taking on some new caffeine habits and share their brains on caffeine:

Effectiveness, Tolerance And Headaches

Why do so many patients coming out of anaesthesia after major surgery feel a headache? It’s because, in most cases, they’re not used to going so long without coffee. The good news? If they wait a few more days, they can start saving coffee again for when they really need it.

The effectiveness of caffeine varies significantly from person to person, due to genetics and other factors in play. The average half-life of caffeine — that is, how long it takes for half of an ingested dose to wear off — is about five to six hours in a human body. Women taking oral birth control require about twice as long to process caffeine. Women between the onset of ovulation and beginning of menstruation see a similar, if less severe, extended half-life. For regular smokers, caffeine takes half as long to process — which, in some ways, explains why smokers often drink more coffee and feel more agitated and anxious, because they’re unaware of how their bodies work without cigarettes.

hownorepinephrinedirectlyPhoto by zoghal.

A 1995 study suggests that humans become tolerant to their daily dose of caffeine — whether a single soda or a serious espresso habit — somewhere between a week and 12 days. And that tolerance is pretty strong. One test of regular caffeine pill use had some participants getting an astronomical 900 milligrams per day, others placebos — found that the two groups were nearly identical in mood, energy and alertness after 18 days. The folks taking the equivalent of nine stiff coffee pours every day weren’t really feeling it anymore. They would feel it, though, when they stopped.

You start to feel caffeine withdrawal very quickly, anywhere from 12 to 24 hours after your last use. That’s a big part of why that first cup in the morning is so important — it’s staving off the early effects of withdrawal. The reasons for the withdrawal are the same as with any substance dependency — your brain was used to operating one way, and now it’s suddenly working under completely different circumstances. Headaches are the nearly universal effect of cutting off caffeine, but depression, fatigue, lethargy, irritability, nausea and vomiting can be part of your cut-off too, along with more specific issues, like eye muscle spasms. Generally, though, you’ll be over it in around 10 days — again, depending on your own physiology and other factors.

Getting Out Of The Habit And Learning To Tame Caffeine

Beyond the equivalent of four cups of coffee in your system at once, caffeine isn’t giving you much more boost — in fact, at around the 10-cup level, you’re probably less alert than non-drinkers. So what if you want to start getting a real boost from caffeine once again, in a newly learned, less dependent way?

Wise Bread has a good roundup of caffeine amountsBuzz Vs The Bulge chart

Braun, author of Buzz, sees it the same way, but still uses coffee — strategically, according to our email exchange:

In practical terms, this means that if you’d like to be able to turn to caffeine when you need it for a quick, effective jolt, it’s best to let your brain “dry out” for at least several days prior to administration. This is actually my current mode of consumption. I don’t regularly drink coffee anymore (gasp).

This from a man who loved (and wore out) his home espresso maker. I love coffee in all its guises. But after 30+ years it wasn’t working for me. For one thing, the problem with caffeine is that there are adenosine receptors all over the body, including muscles. For me, that meant that caffeine made me vaguely stiff and sore, and it aggravated a tender lower back that was prone to spasm. But I also just wasn’t getting a clean, clear buzz from coffee…I drank so much, so regularly, that drinking an extra cup or two didn’t do a helluva lot except, perhaps, make me a little more irritable.

So about a year ago I slowly tapered down, and now I have, if anything, a cup of tea (half black, half peppermint) in the morning. (The amount of caffeine from the black tea isn’t enough to wire a gnat.) Not only does my body feel better now, my brain is clean of caffeine, so I really want (or need) a good neural jump-start, I will freely…nay, ecstatically…indulge. Then I stop and let the brain settle again.

That’s the theory, anyway…and it’s basically true, although I’ll freely admit that sometimes I have an espresso or coffee just because it tastes so damned good.

That’s our attempt at summing up the science and common understanding of caffeine in one post. There is, as you can imagine, a lot more to explore — Braun’s Buzz is a good starting point, but you’ll find your own way from there. What’s the most interesting thing you’ve learned about caffeine, either from reading or personal experience? Share the science in the comments.


  • I’m surprised to read how quickly you build a tolerance to having a daily coffee. I think I’ll see if moving to drinking it strategically is more effective for me.

  • I love the fact most workplaces supply & endorse intake of coffee (which is a drug). This is primarily because it increases work output & concentration amongst workers.

    Strange that we allow ourselves to be medicated by our employers, only to perform better than normal.

    Some would call this, doping.

  • This was an amazing and interesting read to start the monday morning.

    Its a pity that most of the article was explaining how awesome caffeine and coffee is when i’ve just recently (4-5 days ago) quit caffeine for a month to flush my brain out.

    I could go for a cup now…

  • Great Article Kevin – there is so much misinformation about coffee and caffeine on the web…

    Fridge – if anything this article is showing how little benefit caffeine gives us and for many there is plenty of downside to name a few:

    – Withdrawl if you don’t keep the supply going
    – $$ – if you get takeaway – 2x $3 coffees a day ~ $2K per annum
    – Poor sleep quality (not addressed) therefore decreased performance in your day to day

    I personally have found it hard to kick the habit (pathetic I know) – though the times I have after moderate withdrawal symptoms as described here (my wife would attest to the irritability symptom) the upside for me was a feeling of calmness and general well-being, particularly for the couple of weeks post quitting.

    Anyway I’m quitting again and would encourage anyone who’s dependent on caffeine to function to try.

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