It's caffeine. Great big doses in a small amount of time.
It is directly and quickly impacting your neurotransmitters (NTX) adenosine, and dopamine. This is not good in the long term. Caffeine is pretending to be adenosine, your happy sleepy NTXs. Over the long term, caffeine use will start to mess with sleep patterns, robbing you of deep sleep. Thus making you MORE sleepy. Not to mention the excess adrenaline you’ve pumped through you system, this can make you sore and tired. Heck, it might even be kicking up your cortisol release (not sure about that one, but it seems logical). Um, cortisol in the long term destroys brain cells.
What it does to dopamine is even more disturbing. It does the same damn thing that cocaine does. It stops the reuptake; this is leaving excess dopamine in the synaptic gap, more to be picked up by the receiving cell.
You might think this is a good thing, but it's not in the long term. The receiving cell will start to adjust the receptors and you will end up needing more and more (addiction!)
You are way out of homeostasis in your brain if you use a lot of caffeine.
Stopping use after a period of time can lead to depression, terrible headaches, and lethargy. If you start up again to quiet the beast you get the old rebound effect… it will be harder to quit the next time you try.
My advice is to use caffeine sparingly, when you need a jolt. Don’t go using it all the time until it uses you instead of you using it.