Intended for healthcare professionals

Research

Dynamic spread of happiness in a large social network: longitudinal analysis over 20 years in the Framingham Heart Study

BMJ 2008; 337 doi: https://doi.org/10.1136/bmj.a2338 (Published 05 December 2008) Cite this as: BMJ 2008;337:a2338

know your friends

The findings of Fowler and Christakis (1), that happiness
appears to spread through social networks, are an
innovative use of the Framingham Heart Study data. However,
the question still remains to what extent apparent
contagion of happiness to second degrees of separation
could in fact be accounted for by individuals not included
in the Framingham study. The original cohort consisted of
only two-thirds of the individuals of the town between the
ages of 30 and 62.(2) This means that there will be a
sizeable number of socially influential individuals not
included in the social network; whose impact may be being
mistaken for the impact of individuals at a second degree
of separation.

There is enough data within the Framingham heart study to
control for this effect. By only analysing those
individuals 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restricted to the happiness of those individual’s who do
not cite non-heart study individuals as part of their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 individuals, of one degree of separation,
that were not included in the original analysis.

(1) James H Fowler and Nicholas A Christakis, Dynamic
spread of happiness in a large social network: longitudinal
analysis over 20 years in the Framingham Heart Study, BMJ
2008; 337: a233
(2)http://www.framinghamheartstudy.org/participants/origina
l.html

Competing interests:
None declared

Competing interests: No competing interests

27 December 2008
Jonathan A. Mellon
student
St Anne's College, Oxford University, OX2 6HS