- Happy people tend to be at the centre of large groups of other happy people
- Your happiness is related to the happiness of people you may not even know who are up to three degrees removed from you (such as your friend's friend's friend)
- Happiness ripples through social networks, spreading like a contagious disease
- You don't have to be friends with people just like you.
Source: BMJ 2008;337:a2338
Dr Ann Robinson, BMJ Group