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.
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.
Ow!
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.
One of the diseases that coffee helps with is gout. Gout is more or less a special form of arthritis. In most cases the root cause is genetic deficiency in how well your kidneys remove uric acid from your blood. This leads to a buildup of it, and having no place else to go, more and more of it accumulates in your joints. Then your immune system does its best to deal with a foreign substance, and sometimes this leads to runaway inflammation that causes excruciating pain.
Anyway, I can't see a connection between the kidneys' ability to filter out one specific chemical and coffee drinking behavior. Particularly since gout is usually asymptomatic for years while deposits build up in your body, and then you have episodes (attacks) where inflammation gets out of control for a while before subsiding.
I'm not a doctor though, so grain of salt
The crazy thing about coffee and gout is, since it's a diuretic, it should make gout worse, but instead it seems to make it better.
Incidentally, I'm not a doctor either. Just an interested layman. So take everything I said with a grain of salt too. Anyway, gout is super complicated since it involves metabolism AND the renal system AND the immune system AND the joints, so really nobody understands it completely.
I think it's a legitimized/legalized stimulant in place of other stimulants to increase productivity at the expense of numerous subtle risks.
Then I see a lot of people doing both.
An irritated coffee drinker who has been told coffee can be harmful is going to have a whole lot more energy to produce a “counter study”.
That one I'm keeping.
There might be some tiny fraction of coffee drinkers who spaz out about stuff like that, but they'd generally be the ones spazzing out about everything.