Why does coffee make me sleepy?

15 October 2013


Why is it that when I drink coffee it can make me more sleepy? Other people seem to drink coffee and wake up!


We posed this question to the brain panel. Mike - It depends on the time course. I'd be surprised if somebody would drink a cup of coffee then immediately feels sleepy. But I think it's perfectly reasonable to feel sleepy a little bit later on because what's happening when you drink the coffee is that caffeine is complicated but its main effect is to block the action of a transmitter called adenosine which is a sort of dampening down a transmitter if you like in the brain. So, when you block the effect then you feel more awake. Later on, when the coffee effect wears off after it gets eliminated in every 4 hours or so, so when that's gone, the adenosine is still chugging along there and then that may then switch the other way so you feel more sleepy. So, I don't know of a circumstances where you would drink coffee and then suddenly feel sleepy.

Bill- Except perhaps if you had a strong association with coffee as a thing that you took next to going to sleep. Like children here, nursery melodies and they're put to sleep by it. If you had a routine in which you drank coffee and then went to sleep, it may be a signal to sleep and would help you get to sleep. Is that possible?

Hannah - Or maybe he associates coffee with incredibly boring activities like being in the office.

Katie - Feeling really tired?

Hannah - Maybe there's other listeners out there who experiences also. If so, we'd like to hear from you.


When I drink coffee (doesn't matter how it's made or what's in it), I immediately feel a headache coming on and then get very tired. I once fell asleep while in college after I drank a large cup from Starbucks with the intention of staying awake. I wonder why it affects me so differently.

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