Coffee & Sleep: How Does Caffeine Work & Its Effects on Sleep

If you’re like most people, you probably start your day with a cup of coffee or tea. Caffeine is one of the most commonly consumed psychoactive drugs, and it’s found in a variety of sources, including coffee, tea, energy drinks, and chocolate. But how does caffeine work to make us feel more alert? And does the timing in which we ingest caffeine play an important role in whether or not it works for us or against us? Let’s dive deeper into the mechanism behind caffeine and its effects on sleep.

How Does Caffeine Work?

Caffeine is a psychoactive stimulant that works through a variety of mechanisms. One of the mechanisms is a dopamine mechanism. Dopamine is a reward chemical and also an alerting neurochemical. Caffeine seems to play a role in increasing dopamine, but its principal mode of action is on the effects of adenosine.

Adenosine is a chemical that accumulates in our brain from the moment we wake up in the morning. The longer we’re awake, the more adenosine accumulates, which creates sleep pressure. Adenosine is produced when the neurons in our brain combust energy. As our brain is metabolically active throughout the day, adenosine accumulates, and the more adenosine we have, the sleepier we feel.

Caffeine and Adenosine

Caffeine comes into play because it latches onto the welcome sites of adenosine, blocking the effects of adenosine on the brain. When we consume caffeine, it competes with adenosine for the same receptors, which leads to a reduced effect of adenosine. By blocking the effects of adenosine, caffeine makes us feel more alert and awake.

Caffeine’s Effects on Sleep

The effects of caffeine on sleep are complicated. The timing and dose of caffeine can make all the difference. The half-life of caffeine is around 5-6 hours, which means that if you consume caffeine later in the day, it could interfere with your sleep. For some people, even drinking coffee in the morning can disrupt their sleep patterns.

The sleep-promoting effects of adenosine can be delayed by caffeine, and it can take hours for caffeine to wear off completely. Caffeine can affect the quality and quantity of sleep by making it harder to fall asleep, reducing deep sleep, and increasing the amount of time it takes to fall asleep.


Caffeine is a double-edged sword. It can help us feel more alert and awake, but it can also interfere with our sleep. The timing and dose of caffeine are critical in determining its effects on our body. By understanding the mechanism behind caffeine and its effects on sleep, we can make more informed decisions about when and how much caffeine to consume. So, the next time you reach for that cup of coffee or tea, consider the impact it may have on your sleep.