Substance abuse is considered a disease because it changes the structure and function of the brain. Prolonged substance abuse can lead to changes in the brain that result in compulsive drug seeking and use, despite harmful consequences. These changes can be long-lasting and can lead to relapse even after extended periods of abstinence. Additionally, substance abuse can have significant physical and mental health consequences, including damage to organs and systems, increased risk of infectious disease, and psychiatric disorders such as depression and anxiety. Therefore, it is considered a chronic, relapsing brain disease that requires ongoing treatment and management.