So this one's a little late. Today I'll talk a little about addiction.
A brain is a terrible, wonderful thing. It is an incredibly complex organic computer, which takes scads of information and boils them down to the essentials, interprets them, and pounds out appropriate reactions, all within a few hundredths of a second.
We are called the rational animal. Research shows time and again that we are not. The more we learn about ourselves, the more we learn that we are creatures of habit and impulse with a mechanism not for reason, but for justification. In other words, we are less a rational animal and more a rationalizing animal.
Addiction can happen in a number of ways, typically from a misfiring or short-circuit of the brain. Gambling is similar to religion in that it's a misfiring of the learning circuit. All animals seek to understand and master their environment. When cause and effect are absent or distantly linked, superstition is the result. Hence, gamblers believe in luck, athletes believe in silly or disgusting rituals, pigeons believe dancing a certain way will deliver a food pellet, and people worship non-existent sky-beards. One aspect of our learning system is the dopamine response; we get high off of chance. You ever notice how you can't stop playing with a new toy and love it love it love it? And after a few weeks you don't care so much. You're getting high playing with it. Studies have shown that the more certain an outcome, the lower the dopamine response. A 50/50 chance (max uncertainty) sees max dopamine response. Change it to 75/25 (whether 75% success or 75% failure, it's still more certain) and the dopamine response is cut in half. In other words, having mastered a system and made the outcome certain, our system is geared to move on and master something new.
With gambling, that mastery can never come. You cannot change the outcome of a roll of dice. Each roll is as uncertain as the last. Until the cards come up, you cannot know what they'll be. Every time you play is as uncertain as ever. I'd be willing to wager that the most popular games at casinos are also the ones closest to even odds. I know that blackjack and craps are both, when "correctly" played, at nearly even odds (roughly 51% to the house, as I recall). The dopamine response is maxed out for every turn of the cards, every throw of the dice, and it will never get better. When you win, the high is through the roof, and when you lose it's even more terrible.
Coffee also shortcuts the dopamine response. Caffeine really does pump you up and make you feel more awake, but it also does the dopamine thing. It's ticked the part of the brain that says "You won!" and the rest of your brain jumps in saying, "What? What did I win? How? Where? Is that a pony? I won! ... Now what?" Over time, your brain notices similarities and attaches importance to them. You drink from a certain mug more often by chance, your brain attaches more importance to that and you start drinking from it exclusively. You develop a favorite brand, a favorite time of day, a favorite method of preparation... Go on, break a coffee drinker's favorite mug. I dare you. One of the reasons quitting coffee is hard is because when you don't do things the right way, your brain interprets it as the opposite of winning. Everything is wrong forever and you can never win. The other problem, of course, is that, as with all drugs, there's a withdrawal response. Coffee's a stimulant, so your brain ramps down activity in anticipation of being brought back to normal. You get rid of the stimulant and it takes some time for your brain to realize it needs to ramp things back up. This also explains why you need to drink more coffee to get the same effect as you once did. As Terry Pratchett once said, there is such a thing as being knurd (the opposite of drunk), and it's very unpleasant. Hardcore alcoholics need a few drinks just to be normal, hard core caffeine-heads need a few cuppas just to be awake. There are other effects as well.
Cocaine works through dopamine and through seratonin. That's one hell of a one-two combo. It feels good when you take it and bad when you stop. Yowza. Alcohol works through a different system, basically it puts the brakes on your brain (hence it's called a depressant). But when you're not drinking it, the brakes come off (no, you're not smarter when you're knurd; you have fevers and hallucinations and seizures).
Addiction tends to be complex and poorly understood, but one thing is certain: it really, really sucks.