Christakis started his education and academic career in science and medicine. He received his B.S. in Biology from Yale University in 1984, where he ranked top among seniors majoring in the sciences, winning Yale's prestigious Chittenden Prize at the University Commencement. He moved to Cambridge, MA, after graduating, where he received an M.D. cum laude from Harvard Medical School in 1989 and an M.P.H. from the Harvard School of Public Health the year earlier. While at Harvard Medical School, Christakis became interested in medical anthropology, completing his M.D. thesis on ethical standards in transcultural biomedical research (under the direction of anthropologist Arthur Kleinman), and winning the Bowdoin Prize in the natural sciences for his paper, "The ethical and scientific design of an AIDS vaccine trial in Africa."

In 1989, Christakis moved to Philadelphia, PA where he completed a residency in Internal Medicine at the University of Pennsylvania Medical Center and then spent four years studying medical sociology. He started his Ph.D. in Sociology at the University of Pennsylvania as a Robert Wood Johnson Clinical Scholar, and worked as an Assistant Instructor and then Instructor in the Department of Medicine. He worked with Renee C. Fox, a distinguished American medical sociologist; other members of his dissertation committee were methodologist Paul Allison and physician Sankey Williams. Christakis studied the role of prognosis in medical thought and practice, documenting and explaining how physicians are socialized to avoid making prognoses. He argued that prognoses patients receive even from the best-trained American doctors are driven not only by professional norms but also by religious, moral and even quasi-magical beliefs (such as the "self-fulfilling prophecy"). Upon graduating in 1995, he was recruited by the University of Chicago, where he started as an Assistant Professor with joint appointments in Departments of Sociology and Medicine. His first book, Death Foretold: Prophecy and Prognosis in Medical Care, was published by the University of Chicago Press in 1999. Six years after arriving at Chicago, Christakis was awarded tenure in both Sociology and Medicine. However, in 2001, Christakis left the University of Chicago to take up a position as Professor of Medical Sociology at Harvard Medical School; in 2005, he was also appointed as a tenured professor in the Harvard Department of Sociology; and in 2009, he was appointed as a professor in the Department of Medicine at Harvard Medical School. He was elected to the Institute of Medicine of the National Academy of Sciences in 2006.

Nicholas Christakis uses primarily quantitative methods (e.g. statistical models of network formation, social science experiments, and statistics and econometrics for large observational studies) to study social networks and other social factors that affect health. His work has spanned the fields of demography, sociology, sociobiology and health care policy. He is an author or editor of four books, more than 100 peer-reviewed academic articles, and numerous editorials in national and international publications.

In September 2009, Little, Brown & Co. published "Connected: The Surprising Power of Our Social Networks and How They Shape Our Lives" by Christakis and James H. Fowler. Connected draws on previously published and unpublished studies, including the Framingham Heart Study and makes several new conclusions about the influence of social networks on human health and behavior. In Connected, they put forward their "Three Degrees of Influence" rule about human behavior, which theorizes that each person's individual social influence stretches three degrees before it fades out. Christakis is also the author of Death Foretold: Prophecy and Prognosis in Medical Care (University of Chicago Press, 1999), and he has edited two clinical textbooks published by Oxford University Press.

Social Networks and Health

To understand the structure and function of social networks and how they affect health, Christakis led development of a comprehensive dataset regarding a longitudinal network of 12,000 people that had been followed for 32 years as part of the Framingham Heart Study. Using the network, he has studied the spread of health behaviors such as obesity, smoking, eating, and health screening. His investigations also explore the spread of happiness and depression in the network, the influence of heart attacks and strokes in one person on others to whom they are connected, and the socio-biological determinants of networks ties, including genetics.

Using the Framingham Heart Study network and working together with James H. Fowler and other members of his group, Christakis discovered that weight loss and weight gain spread through social ties, arguing that the spread of health behaviors through networks may explain in part the growing epidemic of obesity in the United States over the past several decades. (Watch the research video here, or the interview video here.) In another study, he found that social networks may facilitate quitting smoking. (Watch the research video here.) He also found that happiness may spread through networks; that an individual's happiness correlates to the happiness of their friends' friends, even if they don't know them but are only connected through a social network. For this research, Christakis received the Pioneer Grant from the Robert Wood Johnson Foundation, and the National Institutes of Health awarded him a $11 million grant to start a research program on neighborhoods and networks together with a team of faculty investigators and post-docs that include James H. Fowler, James O'Malley, Alan Zaslavksy, Bruce Landon, Elizabeth Lamont, Rob Sampson, Nancy Keating, Peter Marsden, Tom McGuire, Sam Arbesman, JP Onnela, Coren Apicella, and Niels Rosenquist.

Earlier Research

Prognosis

Christakis's Ph.D. dissertation and early work at the University of Chicago focused on medical prognosis. His book Death Foretold was a product of nearly 10 years of research, combining several prospective, experimental and observational studies.

Hospice Care

During his research on prognosis, Christakis also started to research broader issues involved in medical care for seriously or terminally ill patients. His research on hospice care led to creation of new, large datasets that tracked the clinical, demographic, socioeconomic and market information regarding hospice patients. He also created a dataset of 1.3 million seriously ill patients and their spouses that enabled him to make new contributions to understanding why patients opt for hospice use and how that affects their and their spouses' lives. Christakis research argued that the correct health care choice for terminally ill patients can extend the lives of the surviving spouses during bereavement.

Widow/er Effect

In a series of studies that used a new data set of 1,000,000 couples followed for ten years (the "One Million Couples Dataset"), Christakis studied how having a spouse fall ill or die can affect the surviving spouse. In a series of papers, he documented that men and women are affected differently by the death of the spouse, and that race and the cause of death of the dying spouse also affect by how much the surviving spouse's own risk of mortality increases. He worked on these projects with Felix Elwert, Paul Allison, and Jack Iwashyna.

Nicholas Christakis trained as a general internist and his current practice is exclusively in palliative medicine. Receiving an M.D. at Harvard Medical School, he completed his residency in 1991 at the University of Pennsylvania School of Medicine. He was licensed and certified by the National Board of Medical Examiners in 1990, and the American Board of Internal Medicine in 1993, receiving his Massachusetts License in 2002 upon his move from the University of Chicago to Harvard Medical School. Before coming to Boston, Christakis was a home hospice physician, taking care of home-bound, dying patients. In Boston, from 2002 to 2006, Christakis worked as an attending physician on the Palliative Medicine Consult Service at Massachusetts General Hospital. In 2006, he moved to Mt. Auburn Hospital, a Harvard teaching hospital in Cambridge, MA, where he serves as an attending physician in the Department of Medicine, teaching about end-of-life care and the conduct of clinical research.

Social Networks and Health

Bereavement, Caregiver Burden, Marriage and Health

Neighborhood Effects on Health

Prognosis

End-of-Life Care and Hospice Care

Ethics

Medical Education and Physician Training

Biological Networks