Caffeine, I write this as I sip my 8oz Starbucks blend:
Caffeine belongs to a group of stimulants called xanthines. Considering it's readily available and a reliable pick-me-up for many, caffeine is a very popular drug. After you take some in, its highest concentration in our system occurs within thirty to sixty minutes, and its effects usually last for four to six hours. Caffeine is mildly addictive, as you already know. Some of the signs of withdrawal from a caffeine addiction:
Sleepiness
Feeling overtired (from not having had any caffeine to energize you)
A terrible headache (when you abruptly stop having caffeine regularly)
And you're not the only caffeine-head out there. According to the Center for Science in the Public Interest (CSPI), four out of five Americans have some caffeine on any given day, the average amount being about 200 milligrams a day (approximately equivalent to what's found in two 8-ounce cups of coffee, three to four 12-ounce cans of caffeinated soda, or four 8-ounce cups of tea).
That being said, don't stop enjoying your java, in moderation it isn't bad, neither is sodium nor fat.
By the way caffeine has been shown to enhance your HT experience, usually 16oz of coffee before an action flick does the trick.