Long-time or chronic use of addictive drugs (drug addiction) creates changes in the way the brain transmits information It appears that most drugs of abuse deplete the brain's dopamine receptors, negatively affecting the addict's ability to experience pleasure and reward without progressively increasing quantities of the drug These changes create symptoms of drug addiction Abstinence from the drug of dependency creates symptoms of detoxification and craving Drug treatment and/or addiction treatment must address these physical needs