Stowe Boyd picks up on some very interesting research that suggests that people's happiness is related to the happiness of their friends, their friends' friends, and their friends' friends' friends. Specifically the report includes this:

we found that each additional happy friend increases a person's probability of being happy by about 9%. For comparison, having an extra $5,000 in income (in 1984 dollars) increased the probability of being happy by about 2%.

I suspect the converse is true too. People stuck in networks of unhappy people will tend to be unhappier, which inevitably leads to their friends being slightly unhappier in return. I've seen this effect in organisations where people who are unhappy with their workplace tend to band together to share their unhappy experiences. When this group is in the majority then they may have the chance to change the organisation's behaviour. However when they are in the minority, implying that the majority of the organisation are happy, then it becomes a difficult environment for them which increases their unhappiness, a spiral of despair that can bring the whole group down. That can be very damaging to the individuals, their otherwise happier peers and to the organisation itself. I wonder if this research indicates that these spirals can be unwound by the happy network reaching out to the unhappy one?