I once quit caffeine cold for 6 months: 2 weeks of pure hell then it was like I never craved it until life got real and stressful and I fell off the wagon. Today, I drink my espresso with a dot of lowfat milk now and life is currently too real and stressful to consider trying to drop it again. I do suspect some of us likely have undiagnosed low-level mood disorders leaving us highly functional but discontent and caffeine is the spackling compound used to plug the hole in our souls.
I stopped drinking coffee for a month and didn't notice any difference in my anxiety/mood/etc, so I returned to my regular schedule (3-4 large cups in the mornings).
When work was chill I went to decaf for the morning espresso on weekdays, and enjoyed real coffee on weekends. I took glee in withholding energy from work that I redirected to my personal time.
Then when work picked up, I went back to regular coffee everyday.
I don’t think there’s a hole in my soul though. And caffeine degrades my personality a little bit (to my own judgment).
Caffeine (like all stimulants) can alleviate symptoms of various dopamine-related disorders, like ADHD. I'm sure many people are self-medicating.
This study considers caffeine concumption outside of coffee, so an alternative caffeine source might be worth looking into. That was my takeaway, at least. I also drink espresso, for the caffeine and the noticable ease on my gut compared to drip or pressed coffee.