L-theanine in the adjunctive treatment of generalized anxiety disorder: A double-blind, randomised, placebo-controlled trial

Researchers studied 34 adults with generalized anxiety disorder, a condition involving ongoing, hard-to-control worry. Participants continued their usual treatment and were randomly given either 450 milligrams of L-theanine daily or a look-alike placebo, an inactive treatment, for 10 weeks. The trial was double-blind, meaning neither the participants nor researchers knew who received L-theanine until the study ended. L-theanine did not reduce anxiety symptoms more than the placebo, although it may have helped some people sleep better.

What this means for you: This small study does not provide strong evidence that L-theanine improves anxiety when added to usual treatment. It may be reasonable to ignore L-theanine as an anxiety treatment unless larger studies show clearer benefits.