Caffeine: the drug of choice.
Caffeine is an alkaloid found in notable foods like coffee, tea, and yes, chocolate. Caffeine is a stimulant and diuretic (meaning it makes you pee). It is known to increase awareness or wakefulness, but studies have been equivocal as to whether it affects mental capacity.
I've gone back and forth on caffeine. As a young adult, I didn't drink coffee, tea or soda. So I suppose you could say I was fairly caffeine free. Of course, when I was pregnant and nursing my son I stayed completely away from any caffeine. As I got a bit older, I discovered the joy of coffee and Starbucks came into great popularity, along with a plethora of local coffee shops. I started hitting the caffeine fairly heavily. Then I went through a health-kick phase and did away with the coffee and drank only herbal teas. As all phases do, this one passed. Now I do drink coffee, but it isn't a daily requirement. I don't feel like I'm "addicted" to caffeine. I can take it or leave it. I enjoy my frilly coffee drinks like the new Cinnamon Dolce Latte. Enjoy- not need.
I don't believe that the majority of Americans consider caffeine to be a true "drug". Years ago, I worked with a Mormon. As you may know, many Mormons view caffeine as falling under the prohibitions of the word of wisdom. The odd thing was, she would "cheat" sometimes and have a Coke. Guess she didn't take "the word" too seriously. Must not be a carnial sin....