An addiction is the repeated use of a drug. An addict (person with an addiction) uses the drug again and again. Addicts will continue to use the drug, even if the drug hurts them. Addiction causes cravings for the drug. A craving is an intense need for the drug's effects. Drug tolerance occurs when a person's body adapts to a drug. The body becomes more resistant to the drug and craves the drug all the time. If a dependent person stops taking the drug, they may become very sick or die. Medical help is often required to stop addiction.