The benefits of L-Theanine include relaxation, alertness, deeper sleep and enhanced sleep quality. It is a naturally occurring amino acid that can be found in mushrooms and tea leaves. L-Theanine may aid in you experiencing a state of alert relaxation without the side effects of sluggishness and drowsiness. It may improve cognitive functioning and relieve some stress disorders while also improving overall mood. It may be especially useful in treating anxiety as it enhances alpha brain waves which can result in elevated dopamine and serotonin.