L-Theanine was first recommended to us by a psychiatrist for our younger son when he was in 4th grade and developed a tic due to stress of a teacher in a new school. It didn't do anything for the tic, but our older son took some one day, and really felt great! He's in high school and had been feeling pretty stressed. He said it helped him feel calmer and less anxious while not losing any focus. The good thing is L-Theanine is an amino acid; it's found in green tea. It can cross the blood brain barrier and has a positive effect on alpha-brain waves; it has a relaxing effect, reducing physical and mental stress, boosts mood and cognition. It also acts in concert with caffeine to boost cognitive performance. L-Theanine has been tested on small groups of people with significant sleep disorders, and while it's not overly sedating, it does affect alpha waves and tends to be relaxing. It helps those people with sleep, as it does with anxiety. My husband and I recently added it to our Amazon subscription list of supplements when we read an article in Life Extention Foundation's December 2013 magazine about supplements one should consider adding when facing the flu. It was incredibly timely! No sooner did I get the magazine, read it, stock up and get enough for all the kids, than I got socked with a sinus infection/flu. I have never before gone without a course of antibiotics, but this time really wanted to make the effort. I hunkered down with my supplements - L-Theanine included, ate cooked mushrooms (natural anti-viral) several times, as well as maintaining good hydration, and stayed in bed. I finally made it through my very first painful sinus infection/flu w/o antibiotics! So, yes, I heartily recommend L-Theanine! I'll keep buying it for myself, my husband, and our kids