These days, getting an ultra-customized, caffeinated beverage in one of the many coffee shops around town is the norm for most people. But have you ever forgotten your morning cup of joe? Did you get a headache? Were you irritable? You might have been experiencing withdrawal from a caffeine addiction. Even if coffee's not your drink of choice, other caffeinated beverages like soda or energy drinks have the same effect.
Like most addictive drugs, caffeine provides a reward for the brain. Caffeine mimics adenosine, a molecule that induces sleep and slows down the body's nervous system. When you take in caffeine, it binds to adenosine receptors in the brain instead of allowing the adenosine to bind with them. But caffeine doesn't have the same effect as adenosine. Instead of slowing down the nervous system, caffeine causes it to speed up, and adenosine doesn't get a chance to do its thing. And the more caffeine you take in, the more reliant on it you become to keep going [source: American Running and Fitness Association]. Caffeine also increases dopamine production, which activates the pleasure centers of the brain -- another reason it can be addictive.
Some of the signs of caffeine addiction include restlessness, chest pains, fatigue, nausea and headaches. More than half of coffee drinkers experience withdrawal symptoms when trying to cut out the drink [source: Lowinson].