Gonna go out a limb here and say I have had and still have some very modest level of caffeine addiction. Most offices I've worked in have unlimited collections of coffee, tea, soda, all free for the taking. Which to a man who doesn't value moderation, can be more than a little problematic.
In college, I never really liked coffee, so I guzzled Diet Coke (this was before Coke Zero was a thing) and many, many Red Bulls. My partner was really concerned about all the Red Bull. They read a lot about the effects of all the energy drinks on the market and persuaded me to replace it with something more natural, hence the coffee.
I started to notice two things: I was not focusing super well or really sleeping anymore, and I was very tired sporadically throughout the day. But I shrugged it off long enough, I told myself that I've always had these two problems but something in me snapped.
In the middle of November, I quit drinking caffeine. Full stop. Yes, this had some pretty gnarly withdrawal symptoms and godawful side-effects. I had throbbing headaches for more than a week, and I almost vomited twice. I had a series of meetings that I had to sit through all week, and imagined nothing but crawling into the deepest darkest hole with Tylenol, all six seasons of Downton Abbey and a giant, tersely-worded "Do Not Disturb" sign.
For a point of reference, on an average day I was consuming roughly 500-600mg grams of caffeine. This took the form of 1 French press of coffee, 5 to 7 cans of Coke Zero and one or two cups of English breakfast tea; some days more, some days less (but not much less).
When the more adverse withdrawal stopped things started to level out. I slept phenomally for three nights in a row. I woke up and I was alert, I fell asleep so easily. Then the tiredness throughout the day I was experiencing before, came back. Except this time, only really drinking water and seltzer, I'm starting to realize I wasn't tired, I was really dehydrated. The energy came back and I had more focus again.
I started moving my phone out of my bedroom at night. It got recommended to me a lot. This separation started to help a little bit in the beginning, but I think it was the disconnect from anything on the phone itself that was helping more. As I did this more often, I noticed an actual improvement in my sleep quality.
About a week before Xmas, we had a deadline at work. I went back to pounding caffeine: 2 cups of coffee, four cans of Coke Zero, two days in a row. The results were interesting. My stress level was higher, my headaches were worse, I wasn't more focused, just more annoyed; I had a momentary burst of energy without a whole lot of focus, just nervous manic energy. So it was back off it again.
Then for Xmas, I visited my family in Pennsylvania, which included a major time-zone shift, a 3 hour difference. The jetlag killed. I was wide awake at 1AM which in Seattle was 10PM. This pattern continued to be hard to shake for the whole week even having small amounts of caffeine and Melatonin.
After all of this, we're 6 weeks out from when I started this little experiment, and I'm not sure what it is: correlation vs causality. Is it the presence of more water or the absence of caffeine / fake sugar? No clue; this far out, I feel genuinely better only having a quarter of the caffeine I was having before and that's where I'm going to stay: small amounts of coffee or tea with copious amounts of water.