Drug addiction, also known as substance use disorder, is a chronic and relapsing condition characterized by compulsive drug seeking and use despite harmful consequences. It alters brain chemistry, particularly in areas involved in reward, motivation, memory, and impulse control, leading to intense cravings and loss of control over substance use. Addiction can involve prescription medications, illicit drugs, or other substances, and may result in physical dependence, withdrawal symptoms, health complications, relationship problems, and impaired work or social functioning. Contributing factors include genetic vulnerability, mental health conditions, environmental influences, and early exposure to substances. Effective treatment often requires a comprehensive approach that may include medical detoxification, behavioral therapy, medication-assisted treatment, counseling, and long-term support to promote recovery and prevent relapse.