If you are stressed out and have trouble focusing and paying attention, you may want to consider the dietary supplement l-theanine. It’s found in small quantities in green tea and is thought to be the reason behind why tea is relaxing.
A study looked at what effects l-theanine has on the brain. Subjects were given l-theanine or placebo and then had brain activity measured by electroencephalograph (EEG).
Those who got the l-theanine had increases in alpha brain wave activity, which is associated with relaxation without sleepiness.