Drug addiction is a disease that affects the brain and behavior, causing an uncontrollable urge to use drugs despite the harm they may cause. It involves compulsive drug use even in the face of financial, emotional or health problems. The brain's reward system is hijacked by drugs that flood it with dopamine, making the user want to repeat the experience and "chase that high." This can damage areas of the brain related to judgment, decision making, memory and learning. Cocaine in particular can harm the heart, brain, lungs and other organs, sometimes causing sudden death due to its short half-life and metabolism in the body.