In this book extra I talk with psychiatrist Dr. Vikram Patel. Vikram holds several titles, including the Pershing Square Professor of Global Health and the Wellcome Trust Principal Research Fellow in the Department of Global Health and Social Medicine at Harvard Medical School. He’s also Professor in the Department of Global Health and Population at the Harvard TH Chan School of Public Health. In addition to his academic appointments, Vikram is a co-founder of Sangath, an Indian non-profit committed to improving health across the life span. We discuss his trial of the Healthy Activity Program in India and how you measure constructs like depression.