Caffeine + L-Theanine: Real Calm-Focus, Overstated No-Jitters

Summary

The caffeine + L-theanine "calm focus" stack has genuine, replicated RCT support for a **small** acute edge on attention and reaction time, plus a real (if modest) blunting of caffeine's blood-pressure rise — but the marquee "kills the jitters" claim is mostly false (it dampens the cardiovascular response, not the subjective jittery/anxious feeling), L-theanine as a solo nootropic is overhyped, and there is no tolerance data, so treat it as an acute tool for a focus block, not a daily ritual. ---