Sometime ago I posted some commentary about this study by Doctor Nicholas Christakis and Doctor James Fowler, who used network analysis to aid understanding of obesity. I also posted some commentary on this study on using network analysis to aid the understanding smoking behaviour. Both studies were published in the New England Journal of Medicine. This time Doctors Christakis and Fowler have published a study on happiness in the January 2009 edition of the British Medical Journal, or BMJ for short.

The study design is a longitudinal social network analysis of 4,739 individuals followed from 1983 to 2003. Interestingly happiness, or unhappiness, extends to three degrees. That is to say if you are happy your friend’s friends are also likely to be happy. Unfortunately the reverse also applies! I found this finding of most interest:

'Longitudinal statistical models suggest that clusters of happiness result from the spread of happiness and not just a tendency for people to associate with similar individuals. A friend who lives within a mile (about 1.6 km) and who becomes happy increases the probability that a person is happy by 25% (95% confidence interval 1% to 57%)'.

The study also shows evidence of Dunbar’s theory in action. Professor Dunbar has showed that we have circles of 5, 15, 35, 80 and 150 people, which correspond to our family, our close friends, our colleagues and acquaintances, our club and business affiliations, and finally our village or neighbourhood. Not surprisingly happiness and unhappiness correlate closely with these numbers – at least in this study.

Take a look at the article - its well worth a read. Make sure you have a look at the network diagrams, which are good examples of how to lay out longitudinal data.

If only happiness were as contagious as Ebola I reckon I could solve the world’s woes! Once again it seems networks matter.

Regards Graham