[17] While at the University of Pennsylvania as a Robert Wood Johnson Clinical Scholar, he studied with Renee C. Fox, a distinguished American medical sociologist;[18] other members of his dissertation committee were methodologist Paul Allison and physician Sankey Williams.

[29][30][31] His laboratory is also active in the development and release of software to conduct large-scale social science experiments, pioneering its use beginning in 2009 (e.g., Breadboard, Trellis).

[37][38] In a 2006 paper in The New England Journal of Medicine that analyzed 518,240 elderly couples, he explored how hospitalization of a spouse, and not just their death, might affect a survivor's mortality risk.

[47] In 2010, by exploiting the friendship paradox, a paper analyzed the spread of H1N1 influenza at Harvard University (as part of the 2009 swine flu pandemic) and showed that an understanding of social networks could be used to develop 'sensors' for forecasting epidemics (of germs and other phenomena).

[49] A follow-up paper in 2014 documented the utility of this "friendship paradox" "sensor networks" approach to forecast online trends using Twitter data.

[53] A 2022 paper used another experiment to show how a novel "pair targeting" algorithm could enhance population-level social contagion of the adoption of iron-fortified salt to reduce anemia in mothers and children in India.

[56] A randomized controlled field trial involving 24,702 people in 176 villages in Honduras published in 2024 documented social contagion in diverse health behaviors to two degrees of separation.

[57] Christakis and colleagues also published a series of papers exploring how experimental manipulation of social network structure itself might enhance human welfare.

[59] A 2019 paper in Proceedings of the National Academy of Sciences (PNAS) showed that experimentally re-wiring social networks could enhance human welfare without either redistributing or increasing resources.

[65] Anthropologist Joseph Henrich noted that "the crucial insight from this work is that understanding distinct aspects of cooperation among these hunter-gatherers must incorporate an analysis of the dynamic processes at the population level.

[70] Beginning in 2010, Christakis' lab initiated a program of research to deploy social networks to improve welfare, health, and diverse other social phenomena—for example, facilitating the adoption of public health innovations in the developing world (e.g., India, Honduras),[71][72][57] understanding the origins of economic inequality (published in Nature in 2015),[54] or demonstrating the utility of autonomous agents (AI "bots") in optimizing coordination in groups (published in Nature in 2017).

[75] Another paper that year showed that simply programmed bots could re-engineer social connections among humans in networked groups in order to make them become more cooperative.

[76] A 2023 paper in PNAS showed that simple forms of AI could change humans' ethical behavior towards others (using a cyber-physical lab experiment involving remote-control robotic cars playing the game of chicken).

[84] Christakis' first book, Death Foretold: Prophecy and Prognosis in Medical Care, was published by the University of Chicago Press in 1999 (ISBN 978-0226104706), and has been translated into Japanese.

[19] The book, based on his dissertation, explored the role of prognosis in medical thought and practice, documenting and explaining how physicians are socialized to avoid making prognoses.

It argues that the 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").

[85][86][87] His second book, Connected: The Surprising Power of Our Social Networks and How They Shape Our Lives, was co-authored with James Fowler and published by Little, Brown Spark in 2009 (ISBN 978-0316036146).

[90] Connected draws on previously published and unpublished studies and makes several new conclusions about the influence of social networks on human health and behavior.

"For too long," Christakis writes, "the scientific community has been overly focused on the dark side of our biological heritage: our capacity for tribalism, violence, selfishness, and cruelty.

[68] Christakis' fourth book, Apollo's Arrow: The Profound and Enduring Impact of Coronavirus on the Way We Live, was published by Little, Brown Spark in October 2020 (ISBN 978-0316628228).

[139] In 2012, he wrote a series of online columns for Time with his wife, Erika Christakis, on a range of topics from academic dishonesty to women in the armed services.

They suggested that the critics might be "more concerned with ugly words than the underlying problems" and that policing free expression on campus "denies students the opportunity to learn to think for themselves.

[172] In April 2020, Christakis expressed concern that, in the setting of the COVID-19 pandemic, hospitals and medical schools were seeking to silence faculty and staff who were highlighting problems with the response; he stated that "clamping down on people who are speaking is a kind of idiocy of the highest order.

[178][179][180] In response, Erika (a lecturer on early childhood education at the Yale Child Study Center) wrote an email on October 29 on the role of free expression in universities.

[184][185] During the episode, some students "[asked President] Salovey to remove Nicholas and Erika Christakis from their positions at the helm of Silliman College", and, in a separate development, over 400 faculty members signed a letter on the broader issue of supporting "greater diversity".

[188] In a subsequent op-ed in The New York Times (his only published comment on the events), Christakis argued: "Open, extended conversations among students themselves are essential not only to the pursuit of truth but also to deep moral learning and to righteous social progress.

[191] Alum James Kirchick and former dean of the Yale Law School Anthony T. Kronman have since criticized the university administration for abandoning or not supporting Christakis and his wife.

[180] The New York Times published a coda regarding the episode in August 2018, upon Christakis' appointment as a Sterling Professor, Yale's highest faculty rank.

[204] A "free speech summit" organized by PEN America at Harvard University in 2024 also treated the event as a pivotal one, reflecting a "fundamental shift in campus climate".

"[206] In March 2019, Christakis told Frank Bruni that, partly in response to the events, he worked to complete a long-standing book project on the origins of goodness in society (Blueprint).