Through scientific advances, drug use has been conceptualized through different theoretical lenses. One theory deals with systems-level functioning and the role of family. Drug addiction is commonly defined as a compulsive need for and use of a habit-forming substance with the essential features of tolerance and physiological symptoms upon withdrawal. The consequences of drug addiction in the family are well documented. Not only are the substance-abusing individual's physical health, emotional well-being, and social functioning affected, but family members often also experience stress-related physical and psychological effects such as family disruption, marital discord, interpersonal conflict, financial problems, domestic violence, and child maltreatment. In this entry, the causes and correlates, assessment, and treatment of drug addiction in the family are addressed. Given the magnitude and complexity of ...