Some overlap exists between the technical definitions of drug dependence and addiction, but caffeine use generally falls into the category of drug dependence. If you are dependent on a drug, you need it to function normally. If you are addicted, you use it even if you experience dangerous or negative consequences. Caffeine generally doesn’t pose significant health risks, but if you find yourself unable to quit despite experiencing negative effects, discuss your situation with your doctor.
At moderate levels of intake, most people don’t have negative reactions to caffeine. People who use the term “caffeine addiction” might mean to say they use caffeine habitually to achieve its pleasant effects, which include increased alertness and feelings of well-being. Therefore, a dependence on caffeine is partly due to lifestyle: you enjoy caffeine, so you make it a regular part of your day.
Decreased Negative Effects
When you first start ingesting caffeine, you’ll likely experience increased alertness and perhaps some shakiness or anxiety. But with continual use of caffeine, your body begins to develop a tolerance for the drug, which means the negative side effects of caffeine might diminish. For example, the shakiness and anxiety you experience when you first ingest caffeine might disappear with regular use, making it easier to continue with the habit.
Temporary Withdrawal Effects
Minor, temporary withdrawal effects also promote caffeine dependence. The grogginess you feel in the morning might be due to lack of caffeine, not true exhaustion. After you drink your cup of coffee, the grogginess disappears. To you, this feels as if the caffeine has woken you up. But it's possible that caffeine is canceling out its own negative effects, according to a Bristol University study cited in a June 2010 report from Reuters. In other words, instead of experiencing increased alertness after ingesting caffeine, you're just restoring your wakefulness to a normal level. You feel as if you need a dose of caffeine, but your prior caffeine use is creating the very grogginess you feel the need to combat.
Severe Withdrawal Effects
Contributing to caffeine dependence are the severe withdrawal effects you experience when you miss your regular dose. Caffeine constricts the size of blood vessels in your brain. Your brain anticipates the effects of caffeine by dilating slightly, increasing blood flow and leading to severe headaches. Ingesting caffeine shrinks the vessels, alleviating the headache, so many people combat their withdrawal symptoms with more caffeine, creating a cycle of dependence. Slowly decreasing your intake of caffeine over a few weeks helps make withdrawal tolerable.