While there was no change for the placebo group or for students with minimal anxiety, highly anxious students who took L-theanine had slower heart rates, better visual attention and faster reaction times.
Researchers said that, unlike conventional anti-anxiety treatments, L-theanine did not increase drowsiness, slow reflexes or impair concentration. L-theanine also increased alpha brainwave activity—the type that emerges when the eyes close and the body and mind relax.