The term drug addiction generally refers to a state in which someone is fully dependent on a drug and cannot stop using without help. This can include psychological dependence as well as a physical need for the drug due to the changes it has caused in the brain. Drug abuse refers to problematic substance use that has not necessarily progressed to addiction.
Today, professionals in addiction call these behavioral health conditions substance use disorders rather than abuse and addiction. A substance use disorder may be mild, moderate, or severe. When mild or moderate, it may mean that a person is abusing drugs but is not yet dependent or fully addicted. When classified as severe, it means a person is dependent and has an addiction. Substance use disorders are diagnosed according to eleven criteria in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5).