Comment by crispinb

Coffee has no subjective effect on my energy or arousal or alertness. I just really enjoy the taste and aroma. Every year or two I wonder if I'm getting addicted or inured to caffeine's effects, so take a few experimental weeks off. Sure enough, nothing happens - no withdrawal effects or subjective reduction in alerness/arousal/energy. I return eventually because I miss the taste with my morning toast. I haven't quite generated the curiosity to to read up on it, but I idly wonder if caffeine just doesn't have much effect on some people.