For many, the onset of substance use occurs in adolescence. A subset of adolescents who use substances develop substance use disorders later in life, and some even develop harmful patterns of drinking while still in the developmental stage of adolescence. Why is substance use initiation likely in this age group, and what is the developmental function of substance use behavior? What are the interpersonal processes that influence substance use, and how do relationships with friends and family change during this critical developmental stage? Is it possible to leverage these interpersonal processes to bolster treatment initiation and success? Dr. Sam Meisel answers these questions and more as he discusses the complex social environment of the adolescent and it's pertinence to understanding substance use. Dr. Sam Meisel is a Research Scientist at Bradley Hospital and the Center for Alcohol and Addiction Studies in the Brown University School of Public Health.