Drug addiction is a complex, and often chronic, brain disease. It is characterized by drug craving, seeking, and use that can persist even in the face of devastating life consequences.
Addiction results largely from brain changes that stem from prolonged drug use—changes that involve multiple brain circuits, including those responsible for governing self-control and other behaviors.
Drug addiction is treatable, often with medications (for some addictions) combined with behavioral therapies. However, relapse is common and can happen even after long periods of abstinence, underscoring the need for long-term support and care.
Relapse does not signify treatment failure, but rather should prompt treatment re-engagement or modification. For more information, see Drugs, Brains, and Behavior - The Science of Addiction.
(Source: National Institute on Drug Abuse website. Unless otherwise specified, NIDA's products are in the public domain and can be copied as a whole without seeking permission from NIDA.)