Letters Happiness networks

Know your friends

BMJ 2009; 338 doi: https://doi.org/10.1136/bmj.b293 (Published 28 January 2009) Cite this as: BMJ 2009;338:b293
  1. Jonathan A Mellon, student1
  1. 1St Anne’s College, University of Oxford, Oxford OX2 6HS
  1. jonathan.mellon{at}st-annes.ox.ac.uk

    The findings of Fowler and Christakis, that happiness seems to spread through social networks, arise from an innovative use of the data of the Framingham Heart Study.1 However, the question still remains to what extent apparent contagion of happiness to second degrees of separation could in fact be accounted for by people not included in the Framingham study.

    The original cohort consisted of only two thirds of the people of the town between the ages of 30 and 62.2 Thus there will be a sizeable number of socially influential people not included in the social network whose impact may be being mistaken for the impact of people at a second degree of separation.

    There are enough data in the Framingham Heart Study to control for this effect. By only analysing those who do not refer to friends outside the study’s participants, we could look at a smaller but more complete set of social connections. The dependent variable would be restricted to the happiness of people who do not cite people outside the study as part of their relationships. If the same transmission of happiness at the second degree of separation occurred as with the original data, then we could be more certain of the existence of network effects at this degree of separation as opposed to people, of one degree of separation, who were not included in the original analysis.


    Cite this as: BMJ 2009;338:b293


    • Competing interests: None declared.


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