Interesting. I haven't had any significant amount of caffeine for nearly two years now. I don't drink coffee or sodas and rarely drink (unsweetened) tea. I only consume alcohol on an irregular basis, usually just a couple of beers or a glass of wine every couple of months. I used to be a moderately heavy drinker in my younger years, but that's behind me now as are my partying days. I started L-Theanine to see if would help improve my sleep by settling my mind a bit at night, but I don't think it worked that way for me. Hard to tell really. I also take L-Arginine, but that stuff tastes horrible. I was doing the powder form but switched to capsules because it's foul tasting even if mixed with something else. That does have an effect, but it's not magic. I probably get enough L-Arginine from food anyway.