Substance abuse, or substance use disorder, is the uncontrollable urge and misuse of a substance despite its negative consequences. Substance use disorder can involve illicit (e.g., heroin, cocaine, ecstasy) and legal (e.g., prescription medications, cigarettes, alcohol) substances.The term refers to the repeated use of a substance that produces severe behavioral, psychological, and physical issues. For example, substance abuse may result in missing important events, such as trips, work, or school, or using it in potentially hazardous conditions, like driving. In addition, it can result in substance-related legal issues, substance-induced anxiety disorder, or prolonged substance use that interferes with friends and family.