Nicholas Christakis

Lore & Background

Nicholas A. Christakis (born May 7, 1962) is an American and Greek sociologist and physician. He is the Sterling Professor of Social and Natural Science at Yale University, where he directs the Human Nature Lab and co-directs the Yale Institute for Network Science. His defining characteristic is his research on social networks and the social, economic, biological, and evolutionary determinants of human welfare, including the behavior, health, and capabilities of individuals and groups. Christakis was born in New Haven, Connecticut, to Greek parents who were graduate students at Yale; the family returned to Greece when he was three, making Greek his first language, and moved back to the United States when he was six. He earned a B.S. in biology from Yale, an M.D. from Harvard Medical School, an M.P.H. from the Harvard School of Public Health, and a Ph.D. in sociology from the University of Pennsylvania. His career includes professorships at the University of Chicago and Harvard before moving to Yale in 2013. He was elected a Fellow of the National Academy of Sciences in 2024, the National Academy of Medicine in 2006, and the American Academy of Arts and Sciences in 2017. He received an honorary degree in economics from the University of Athens in 2021 and the Barry Prize for Distinguished Intellectual Achievement in 2024. He was named to the *Time* 100 in 2009 and to *Foreign Policy*’s top global thinkers in 2009 and 2010. His research uses quantitative methods including experiments, mathematical models, and statistical analyses, focusing on network science and biosocial science. He pioneered the study of hyper-dyadic network effects, examining how illness and death propagate through social networks of family, friends, and colleagues.

Reader's Guide

Christakis’s research centers on how social networks influence human behavior, health, and welfare, using quantitative approaches such as experiments, mathematical models, and statistical analyses. His early work examined physician decision-making and end-of-life care, leading to studies of the widowhood effect—the phenomenon where a spouse’s death increases the survivor’s mortality risk. He developed methods to estimate causal network effects, such as analyzing how the death of an ex-wife affects a man’s risk of death, and explored how a spouse’s hospitalization, not just death, impacts the survivor. Building on these dyadic studies, he expanded to hyper-dyadic network effects, tracing how illness and death propagate through broader social ties of family, friends, and colleagues. His work integrates sociology, evolutionary biology, behavior genetics, and epidemiology, and his lab has pioneered software for large-scale social science experiments since 2009. Christakis’s findings have reshaped understanding of how social connections spread health outcomes, contributing to network science and biosocial science as interdisciplinary fields. His election to the National Academy of Sciences in 2024 and recognition as a Time 100 influential figure underscore his impact on social and natural science.

Did You Know?

• Nicholas A. Christakis was one of the researchers who developed and applied new models and methods to emerging data about online social networks beginning in the late 1990s.
• Christakis worked alongside James H. Fowler on social network research.
• Christakis in the context of work by sociologists, political scientists, and physicists on social network analysis.
• Christakis's research involved 'digital traces' regarding face-to-face networks.