This isn't super surprising based on my personal experience. I take theanine in the morning to help clear my mind before working and also before bed to stop my mind from racing.

I have found that taking caffeine and other prescription stimulants(Adderall)have a negative effect in some ways increasing my anxiety or otherwise hindering my ability of outside-the-box thinking. Subsequently I have stopped taking Adderall completely for about a month now and I feel a ton better.