A cup of tea seems to be the best thing for someone who has had some kind of shock or stressful ordeal. Maybe there is something in tea that has this calming effect. Although tea contains caffeine (A stimulant) it also contains an amino acid called L-Theanine. It is not unique to tea but the tea plant seems a particularly rich source. When L-Theanine has been given to people in clinical studies many of the positive effects of tea can be reproduced.