Caffeine addiction is the excessive and/or harmful use of caffeine over a period of time, which has negative effects on your health, social interactions, or other areas of your life. As caffeine is a widely accepted and used drug, many people don't believe caffeine can be addictive. Caffeine content can range from as much as 160 milligrams in some energy drinks to as little as 4 milligrams in a 1-ounce serving of chocolate-flavored syrup. Even decaffeinated coffee isn't completely free of caffeine. Caffeine is also present in some over-the-counter pain relievers, cold medications, and diet pills. These products can contain as little as 16 milligrams or as much as 200 milligrams of caffeine. In fact, caffeine itself is a mild painkiller and increases the effectiveness of other pain relievers.