Dynamic spread of happiness in a large social network: longitudinal analysis over 20 years in the Framingham Heart Study
Fowler and Christakis analysed the Framingham Heart Study social network, following 4,739 people from 1983 to 2003. Happy and unhappy people formed clusters reaching up to three degrees of separation, and people surrounded by many happy people, or central in the network, were more likely to become happy later. A friend living within a mile who became happy raised a person's probability of being happy by about 25 per cent; smaller effects appeared for spouses, nearby siblings and next-door neighbours, and none between coworkers. The influence weakened over time and with geographic distance. The authors conclude that happiness depends on the happiness of connected others and can be seen as a collective phenomenon.
Fowler and Christakis analysed the Framingham Heart Study social network, following 4,739 people from 1983 to 2003. Happy and unhappy people formed clusters reaching up to three degrees of separation, and people surrounded by many happy people, or central in the network, were more likely to become happy later. A friend living within a mile who became happy raised a person's probability of being happy by about 25 per cent; smaller effects appeared for spouses, nearby siblings and next-door neighbours, and none between coworkers. The influence weakened over time and with geographic distance. The authors conclude that happiness depends on the happiness of connected others and can be seen as a collective phenomenon.
Written from the abstract (PubMed) and journal record (Crossref), 2026-11-03.
What our sources record
Recorded when this source was checked, figures included, with page references and quotation marks removed.
Fowler, J. H., & Christakis, N. A. (2008). Dynamic spread of happiness in a large social network: longitudinal analysis over 20 years in the Framingham Heart Study. BMJ, 337, a2338. doi:10.1136/bmj.a2338 https://doi.org/10.1136/bmj.a2338