L-Theanine: one of the main psychoactive compounds found in tea. L-theanine is extremely safe and has been shown to mitigate the negative aspects of caffeine, such as anxiety, increased blood pressure and diminished sleep quality, while possibly improving upon the positive aspects. Its ability to enhance attention has been repeatedly verified. A recent systematic review of the effects of l-theanine and caffeine has confirmed that the combination seems to improve aspects of attention. The combination of L-theanine and caffeine may improve attention more than caffeine alone. L-theanine alone has been shown to boost alpha brain waves, a pattern of brain activity correlated with relaxed attention. In one recent animal study l-theanine consumption was associated with about a 25% increase in BDNF and about a 100% increase in NGF in the hippocampus. L-theanine taken with caffeine is one of the most reliable and safe nootropic stacks for improving focus.