"Medium-to-high level caffeine users, however, did not become any more anxious after caffeine, implying that regular consumption helps build up a resistance to its anxiety-inducing effect. People in this group who were genetically predisposed to anxiety drank more coffee than the rest, suggesting mild feelings of tension might even contribute to their enjoyment of the caffeine buzz."

Drinking coffee doesn’t make you more alert, caffeine study reveals. Ringing a few bells this.