Does L-Theanine help with anxiety?

Conclusion: The reviewed studies presented evidence that green tea influences psychopathological symptoms (e.g. reduction of anxiety), cognition (e.g. benefits in memory and attention) and brain function (e.g. activation of working memory seen in functional MRI). The effects of green tea cannot be attributed to a single constituent of the beverage. This is exemplified in the finding that beneficial green tea effects on cognition are observed under the combined influence of both caffeine and l-theanine, whereas separate administration of either substance was found to have a lesser impact.

Conclusion: Medicinal herbs may be promising for the treatment of anxiety. However, these results should be considered preliminary because of the unconvincing sample sizes, together with the potential effectiveness of placebos.