What Caffeine Is/Does
Caffeine’s main function is getting into your brain and blocking the possible uptake of AMP.
This matters because AMP is how your brain knows you’re tired. When caffeine blocks the receptors in your brain, AMP can’t enter them, and you can’t sense it, keeping you blissfully unaware of the impending tiredness.
Adjustments to Energy Levels
In the short term, caffeine does not make you sleepy.
In fact, it does exactly the opposite: it reduces your ability to feel sleepy at all. Tiredness is reduced while energy perception goes up and mental performance improves—especially in things like concentration.
Caffeine is actually great for reducing both feelings of tiredness and sensitivity to distractions.
Other benefits also speak to this not-sleepy-ness:
- Improved memory formation
- Better ability to focus
- Increased exercise performance
- Reduced fatigue-sensitivity
- Better muscular chemistry
So, it’s clearly not making you sleepy now, but can it affect tiredness in other ways?
When Caffeine Won’t Wake You Up
First of all, caffeine can’t just undo tiredness. We’ve all tried to caffeinate late in the day when we’re already tired, and the results are mixed at best.
Once you’re already clearly signaling for tiredness and the need to sleep, blocking receptors will have a limited effect. The process of getting tired and preparing for sleep is more complicated than just the receptor changes.
Late-day caffeine just doesn’t have the same effects, especially when combined with other environmental changes like the loss of blue light when the sun goes down. At some point, the brain is already saturated with Adenosine-bound receptors, and it’s inevitable to get—and stay—tired.
Crashing and Post-Caffeine Energy Changes
Not only is caffeine not always the solution, but it may also be a contributing factor to your tiredness when that saturation point eventually comes around.
There’s no mystery to it—the feeling of tiredness after caffeine’s effects wear off, known as the crash, can be intense. This usually reflects the difference felt between artificially reduced tiredness-signaling and then your body’s ultimate realization that you do have a lot of AMP in your system.
As caffeine’s roughly 6-hour half-life is up, you will start feeling the drop-off. It could be more intense than the usual onset of tiredness due to the speed of this process, especially if you’re continuing to consume caffeine during the day.
In this way, caffeine use often offers a short-term reward but comes with some longer-term changes to your energy levels throughout the day. It’s not just spiking you in the morning (e.g.) but also sharpening the descent into tiredness later on.
Sleep Quality
This is the real kicker if you’re crutching yourself on caffeine: over-use can easily have a negative impact on your sleep quality.
Sleep can become fragmented when caffeine hasn’t cleared the system, and the inherent anxiety of stimulants can damage the restfulness of sleep. It’s hard to get high-quality deep sleep if you’re caffeinated towards bedtime.
If your caffeine use is interrupting your sleep quality, you are going to experience more profound tiredness. Daytime energy levels will be lower during these periods of caffeine-interrupted sleep, with hormonal wellbeing and mental performance dropping off a cliff.
Of course, this is not an inevitable result of using caffeine.
It’s a compound that you can use responsibly without causing serious disruption to your sleep quality or quantity. If you’re using it in reasonable doses (under 450mg a day) and mostly using it 8+ hours before bed, you may not suffer any side effects.
Just be aware that there are side effects and possible misuse consequences. It’s a great drug for helping get the most out of your day, but it can have knock-on effects that cause tiredness, fatigue, and irritability if you’re being careless.
In Summary…
Here’s the simple version: caffeine won’t make you sleepy, but your bad caffeine habits might.
You can use caffeine to fend off tiredness and pick yourself up if you’re tired. It shouldn’t, however, become a crutch to your bad sleep habits or lack of lifestyle-management.
In those scenarios, it can cause you real cyclical issues of being tired, over-caffeinating, ruining your sleep quality, and then being more tired.
We want to use caffeine like adults and make sure that use stops at a time where we are in control and have plenty of time to wind down into a relaxed, low-anxiety evening.
Enjoy your caffeine when you need it, and don’t just top up endlessly. You will hit a brick wall of tolerance, and you’ll have to take a step back—and a month off—before you can get the same benefits!
References
- Caffeine may interrupt or crutch high-quality sleep: https://dx.doi.org/10.2147%2FRMHP.S156404
- Caffeine may reduce sleep quality and quantity: https://doi.org/10.1016/j.smrv.2016.01.006
- Caffeine worsens anxiety in susceptible patients: https://doi.org/10.1001/ARCHPSYC.1992.01820110031004
- Combined benefits of Caffeine and L-theanine: https://www.tandfonline.com/doi/abs/10.1080/1028415x.2016.1144845
- Caffeine can improve cognitive performance: https://doi.org/10.3233/jad-2010-091315
- Tolerance to caffeine and other alkaloids: https://doi.org/10.1007/BF02245285
- Caffeine combats sleep-deprivation symptoms – but decreasingly over time: https://doi.org/10.1111/jsr.12681
- Acute and chronic results of caffeine withdrawal and side-effects: https://doi.org/10.1177%2F026988119100500206
