I've heard this too, but green tea, for whatever reason, absolutely ratchets up anxiety for me. Black coffee can if I have too much, but is surprisingly less likely to
Same here. I got into loose leaf tea to cut down on coffee drinking. I tried all sorts of greens but had to stop drinking it because it made me some combination of anxious and easy to anger.
I experience the same effect and have heard others say the same thing. L-theanine activates excitatory neurons and also increases dopamine levels in the brain.
