L-Theanine for Anxiety Relief

Research suggests that L-theanine may help reduce stress and anxiety responses, with a body of evidence spanning multiple randomized controlled trials, systematic reviews, and a 2024 meta-analysis generally supporting its potential to lower perceived stress, attenuate physiological markers of stress such as cortisol and sympathetic nervous system activation, and improve self-reported anxiety symptoms under stressful conditions. Studies indicate these effects may occur through modulation of neurotransmitter systems and increases in relaxation-associated brain wave activity, and some trials have also observed improvements in sleep quality and cognitive function alongside anxiety reduction. However, the evidence is not uniformly positive — a 2022 network meta-analysis found L-theanine did not demonstrate statistically significant benefits for anxiety when compared directly against other herbal interventions, at least one RCT found no significant impact on anxiety or stress biomarkers during an acute stress challenge, and a 2025 review cautioned that the overall body of human clinical trial evidence remains inconsistent and limited in rigor. Many of the supporting studies involve small sample sizes and short durations, and researchers across multiple reviews call for larger, more methodologically robust trials before firm conclusions can be drawn.