Drugs can be bad for you in lots of ways. Even occasional or experimental drug use can be dangerous, since drugs can have unexpected adverse health effects even with one use; and drugs affect your ability to exert good judgment, making it more likely that you might engage in risky behaviors that can have serious consequences, such as driving while intoxicated. Prolonged drug use can cause all sorts of medical problems—like lung cancer, heart disease, liver disease, and addiction. When someone is addicted to drugs, they become the most important thing in that person's life, causing them major problems at school, home, and work.