to combat this, i started researching and led me to matcha tea. i just drink a lot of matcha tea now and i found it helps with my anxiety and i'm generally more calm. it still has caffeine at lower doses so it still gives that caffeine feeling so what i'm feeling might be a placebo but definitely helps.
i did not quit coffee 100% though, i still drink it from time to time but not as often. it used to be > 4 cups of coffee per day (sometimes espresso shots) and now to 1-2 cups every 5-7 days.
i have to say my coffee journey was fun though, for the last 10 years i started from starbucks, to roasting my own beans, to aeropress and drip, to a full fledge espresso machine.
I recently quit drinking coffee hoping I could stop grinding my teeth in the night. It hasn't helped yet, but I quit only about 3 weeks ago.
An aside, grinding your teeth in the night is very problematic because it's not something you can directly resolve unless you get a mouth guard. Trying to pinpoint stressors in my life has been an arduous process.
Sleep is easily the cornerstone of a quality day to day life. I love coffee, the taste, the ritual, etc. But I need to stop.
Another pet theory I have is that a confounding variable in these studies is often the amount of work someone has to do, and the type of work.
Someone drinking 4+ cups of coffee likely has a reason to be that productive. Which may result in more intellectual stimulation, a higher income, and other differences that makes the two groups very different.
I'd like to see studies where the same individual both drank 4+ cups of coffee everyday for 6 months, and then quit caffeine entirely for 6 months and measure the changes in health, and output collectively but on an individual basis.