The Science Behind the Coffee-Withdrawal Headache

Love coffee? It’s one of life’s small treasures — the delicate aroma of a cappuccino, the sour zest of an espresso, and the ardent texture of a flat white are hard to beat. Coffee is wonderful. And enjoyed in small amounts and somewhat infrequently, coffee is fairly harmless. But something slightly sinister happens when we gain a dependency on it, and it can be an unpleasant surprise…

Our brains are notified of the need for sleep by measuring a chemical which is produced in small quantities through out the day, and begins to build up in higher amounts near the end of the day. When we enter our soft slumber, this chemical, adenosine, gets cleared out by the processes of sleep, during which brain wave activity changes and our nervous system is less reactive to external stimuli. Lots is happening while we are “resting,” and the clearing out of stagnant chemicals is just one of the tasks our brains accomplish while we are in repose. Once we are awake, the adenosine begins to build up again, slowly. The more of it we have in our brains, the more we begin to perceive ourselves as “getting tired.” We of course eventually fall asleep, and our brain clears the adenosine out and resets it to to a low (or empty) quantity for the next day, when the cycle starts all over again.

When we consume coffee, the caffeine essentially works to block our brain’s ability to measure this chemical. In the most basic of definitions, our brain has “chemical receptors” to which certain types of chemicals bond. When the adenosine chemical “connects” to its receptor, that’s how our brain is aware of how much of it is currently present within the brain. However, when we drink caffeine, it gets in between the chemical and the receptors, preventing them from bonding. So even though we may have an abundance of this chemical in our brain because we’ve been awake for a long time or didn’t get enough sleep last night, caffeine creates the illusion that our brain has no adenosine present at all, and thus is properly well rested with no need for sleep at the moment. This gives the false appearance that we may continue functioning with a clear-head and alert state of mind, since our brain isn’t trying to get us to wind down for sleep, as it currently seems like we don’t need any! We can think of the receptors like smoke detectors – caffeine stops the receptors from detecting the smoke.

One day, when we don’t have our typical 1 or 2 (or more) cups of coffee, we may experience a staggering headache. The reason we get what we perceive as a “headache” from caffeine withdrawal is because, eventually, our brains begin to realize the trick caffeine is playing, and in true evolutionary spirit, it attempts to adapt by creating new receptors to measure the adenosine levels. It recognizes that we are blocking the receptors, and by creating new ones, there won’t be enough caffeine to block all of them. This is why, over time, we must consume more caffeine in order to feel similar effects. The brain simply adjusts to the caffeine and tries to return our sleep cycle to normal. The headache arises because when we do not consume any caffeine, our brain falsely believes we’re significantly more tired than we actually are, because these receptors are measuring ALL of the adenosine in our brain, instead of just the modified amount it had gotten used to measuring when the caffeine was blocking it. We are thus totally crashing as a result of detecting the virtual plethora of adenosine that it wasn’t detecting before.

So there you have it. The functionality of WHY our brains seem to revolt when we don’t give it that daily dose of caffeine. Best thing to do? Give a clean reset — no caffeine for at least a week, and then start to slowly enjoy coffee again in moderate doses.