The problem with caffeine is the longer-term effects, which tend to spiral. For example, once the adrenaline wears off, you face fatigue and depression. You take more caffeine to get the adrenaline going again. As you might imagine, having your body in a state of emergency all day long isn't very healthy, and it also makes you jumpy and irritable. The most important long-term problem is the effect that caffeine has on sleep.
Adenosine reception is important to sleep, and especially to deep sleep.
The half-life of caffeine in your body is about six hours. That means that if you consume a big cup of coffee with 200 mg of caffeine in it at 3 p.m., then by 9 p.m. about 100 mg of that caffeine is still in your system. You may be able to fall asleep, but your body probably will miss out on the benefits of deep sleep. That deficit adds up fast. The next day you feel worse, so you need caffeine as soon as you get out of bed.