L-Theanine, an amino acid predominantly found in green tea, exhibits neuro-regulatory properties that may provide targeted benefits for individuals experiencing depression, anxiety, and insomnia, while also supporting cognitive performance under stress.

This paper reviews its mechanisms across neurotransmitter modulation (serotonin, dopamine, and GABA enhancement), stress axis regulation (HPA axis balance), and sleep-wake cycle optimization via melatonin pathways.

Evidence from clinical trials suggests that L-Theanine supplementation can improve mood stability, reduce physiological stress markers, and enhance attentional control, particularly in students, high-demand professionals, and menopausal women.

The potential synergistic role of L-Theanine with other nutraceuticals is also discussed, providing a framework for integrative nutritional strategies in mood and cognitive health management.