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For a long time I had only a vague idea of what caffeine addiction actually meant in scientific terms. I'd read that, as with many drugs, you build up a tolerance to caffeine and need more and more to achieve the same effect—but most articles didn't go into detail about exactly why. A year or two ago, I came across the fascinating blog You Are Not So Smart, written by journalist David McRaney "to publicly explore our self delusions through literary journalism." Most of the posts focus on psychology, presenting a commonly held belief about the way we think and then meticulously explaining why it's wrong, often over the course of several thousand words. The one McRaney wrote about coffee stood out to me because it's the best explanation I've seen of caffeine addiction.
It's a complex post, but he puts the nut in the first two lines:
The Misconception: Coffee stimulates you.
The Truth: You become addicted to caffeine quickly, and soon you are drinking coffee to cure withdrawal more than for stimulation.
The main effect of caffeine on your body is that it blocks adenosine. As McRaney explains it:
Caffeine is an adenosine antagonist. This means it prevents adenosine from doing its job. Your brain is filled with keys which fit specific keyholes. Adenosine is one of those keys, but caffeine can fit in the same keyhole. When caffeine gets in there, it keeps adenosine from getting in. Adenosine does a lot of stuff all throughout your body, but the most noticeable job it has is to suppress your nervous system. With caffeine stuck in the keyhole, adenosine can’t calm you down. It can’t make you drowsy. It can’t get you to shut up. That crazy wired feeling you get when you drink a lot of coffee is what it feels like when your brain can’t turn itself off.
To compensate, your brain creates a ton of new receptor sites. The plan is to have more keyholes than false keys. The result is you become very sensitive to adenosine, and without coffee you get overwhelmed by its effects. After eight hours of sleep, you wake up with a head swimming with adenosine. You feel like shit until you get that black gold in you to clean out those receptor sites. That perk you feel isn’t adding anything substantial to you—it’s bringing you back to just above zero.
And, McRaney points out, it takes just seven days to become addicted to caffeine. There are other elements to the effect caffeine has on you, including stimulating your adrenal glands and releasing dopamine (I'd highly recommend reading the whole blog post, which isn't even that long). Basically, there's a reason that in 2005 a neuroscience professor at Johns Hopkins tried to have caffeine withdrawal classified as a mental disorder in the Diagnostic and Statistical Manual of Mental Disorders.
On the other hand, though, Kate Schmidt pointed out earlier this week that studies have also shown all kinds of health benefits associated with coffee, including a lower risk of type 2 diabetes, colon cancer, heart disease, and possibly Alzheimer's (or at least a delayed onset). So maybe I will learn to drink it. Eventually.