Dr. Nicholas Christakis, who studies the mathematical, social, and genetic determinants of social network structure, explains how happiness flows one person to another.

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Nicholas A. Christakis, MD, PhD, MPH, is a social scientist and physician who conducts research on social factors that affect health, health care, and longevity. He directs the Human Nature Lab at Harvard University. He is Professor of Medical Sociology in the Department of Health Care Policy at Harvard Medical School; Professor of Medicine in the Department of Medicine at Harvard Medical School; and Professor of Sociology in the Department of Sociology in the Harvard Faculty of Arts and Sciences. Dr. Christakis’ lab is currently focused on the relationship between social networks and health. People are inter-connected, and so their health is inter-connected.