I'm not sure if I would call caffeine addiction a mental disorder unless it was way out of hand, the caffeine was being abused, and overall the problem was very detrimental to the user's health. I used to live off of caffeine until I got on Lithium. I stay away from caffeine now because if I have too much, it messes with my Lithium levels and makes me depressed again. I used to despise water but now I live with it.