Sorry, I don't know the side effects of L-theanine, but, for whatever it is worth, it does not work for me.
When I read this initial post in March I ran right out and bought a jar of 60 200 mg. tablets and took one. Absolutely no effect.
For those helped by L-theanine, I'm glad you found it to be effective. I have a jar with 59 tablets left I would like to get to you.
To Cally, I find chamomile tea somewhat relaxing, as opposed to green tea.