It's an important distinction to make in this discussion, which largely boils down to "off label use", whether we're talking about drinking simply too much coffee or people with developing brains getting too much thc.
Caffeine has negative side effects. It is an addictive psychoactive drug. Its effects are mild, but, to repeat, it is an addictive psychoactive drug.
Even moderate use can cause sever anxiety in some people. L-theanine is a great counter to this. Green tea naturally has L-theanine in it and that is likely why people who drink green tea do not report anxiety (at least in significant numbers) while coffee drinkers do.
FWIW Matcha has even more L-theanine that green tea.
From personal experience, it caused my medications to stop working.
Now that I did not know. Given that l-theanine is a natural constituent of green tea (though I don't know offhand in what amount) I figure there would be more mention of this! A casual search doesn't reveal much, and even examine.com (https://examine.com/supplements/theanine/research/#pharmacol...) doesn't have anything listed. Ugh.
Then again almost no one mentions that 5-HTP can cause horrible things to happen to your heart. :/
I just quit cold turkey three days ago and suffered through two days of horrible headaches. I don't want to ever get hooked again.
I think the most universal things everyone should be doing are: get more exercise, and get more sleep.
/r/nootropics, common thread is as follows:
OP: "Help, I have bad anxiety every day, what should I take for it?"
re: "Do you drink coffee?"
OP: "Yes, about 4 cups a day."
re: "Stop drinking coffee and come back in a week and tell us how you are doing."
1 week later.
OP: "My anxiety is gone!!"
Caffeine has negative side effects. For some people those side effects are really bad.
Also caffeine messes up sleep cycles. After seeing sleep study results, I won't touch the stuff after 10am or so, if even that late.
Alcohol is even worse in this regard, it will just ruin your sleep cycles at night.
Edit: Let me emphasis this for anyone reading:
YOU WILL NOT GET DEEP SLEEP IF YOU HAVE A NIGHTCAP.
Yes, you will get drowsy, drink enough and you will pass out. The restorative quality of the sleep you get that night will NOT be good. I've seen first hand the sleep study results from this. The effect is so obvious that even the questionable sleep quality results that wrist based wearables give you can easily and consistently show this effect.