Anecdotally, Caffeine+L-Theanine makes my anxiety worse and my ability to focus severely decreased, basically the opposite effects of what people seem to achieve with this combo.
As compared to caffeine alone? Or as compared to nothing?
Caffeine alone. I should probably give it a try without caffeine, and probably take a T-break on the caffeine too. But I'm not sure I have the motivation to do that.