I have panic attacks and my doctor suggested I try l-theanine. I tried 100 mg two days in a row and I thought I had found the miracle supplement. It worked better than anything I have ever tried. However, on the third day, I took it just as I felt myself going into some anxiety and I had the worst panic attack I have ever had. The worst weakness and dizziness. I don't want to take it again in fear it made the attack worse or was it just the timing. I made the mistake of going online and the reviews made it sound horrible but the worst reviews were folks that were on other drugs and I don't take anything else. That supplement is amazing.