Theanine is an amino acid primarily found in plant or fungal species. It is commonly consumed as a component of green tea and has been used historically as a relaxing agent. Lu et al (2004) compared the effect of theanine and Alprazolam on anxiety states in 16 healthy adults.  Alprazolam is a psychiatric drug prescribed for anxiety and panic disorders. The experiment revealed that there was no difference in the influence of the drug or theanine. Theanine supplements are a viable option for anxiety relief if pharmacotherapy is not your cup of tea.