Promotes alpha brain wave activity - the same relaxed-but-alert state you're in just before sleep, or right after a good meditation.

L-Theanine increases cortical alpha wave activity — the brain state linked to being relaxed yet alert — while blunting stress-induced cortisol responses. Together, this quiets sympathetic arousal and mental overactivity at bedtime, easing the transition into sleep.

Clinically, a systematic review and meta-analysis found that L-Theanine significantly improved subjective sleep onset latency, daytime function, and overall sleep quality. These findings support the idea that L-Theanine works by reducing the hyperarousal and stress that interfere with falling and staying asleep.

https://www.sciencedirect.com/science/article/pii/S1087079225000292#bib33

https://pubmed.ncbi.nlm.nih.gov/34562208/

https://pubmed.ncbi.nlm.nih.gov/31623400/

https://pmc.ncbi.nlm.nih.gov/articles/PMC11811612/