… many researchers have found that religious people are happier. Indeed, a common finding is that religiosity is among the closest correlates of life satisfaction, at least as strong as income. Why that might be true remains a matter of some controversy (like almost everything else about religion). However, to our surprise, the linkage between religion and life satisfaction seems to be virtually identical in form to the linkage between religion and good neighborliness:

• As with good neighborliness, the correlation between religiosity and life satisfaction is powerful and robust. It remains strong even when we hold constant the same long list of other factors that might have made the correlation spurious. Other things being equal, the difference in happiness between a non-churchgoer and a weekly churchgoer is slightly larger than the difference between someone who earns $10,000 a year and his demographic twin who earns $100,000 a year.
• As with good neighborliness, religious people are more satisfied with their lives mostly because they build religious social networks, thus reinforcing a strong sense of religious identity. A person who attends church regularly but has no close friends there is actually unhappier than her demographic twin who doesn’t attend church at all.
• As with good neighborliness, religious friends remain very important, even when we compare people with equal numbers of friends overall, and in that sense religious friendship seems supercharged. Moreover, as with good neighborliness, the effects of religious social networks do not depend on maintaining a religiously homogeneous social environment; on the contrary, people whose closest friends are all from the same religion are, other things being equal, less happy than those whose friends are diverse.
• As with good neighborliness, theological and denominational differences appear to have virtually nothing to do with the linkage between life satisfaction in religiosity.
• As with good neighborliness, comparing changes in religiosity and in life satisfaction in our 2006 and 2007 interviews suggest that the correlation might be causal. People who become more religious become happier.

In short, as with good neighborliness, the religious age in life satisfaction has less to do with faith itself than with communities of faith. For happiness as for neighborliness, praying together seems to be better than either bowling together or praying alone.

American Grace: How Religion Divides and Unites Us by Robert D. Putnam and David E. Campbell (Simon & Schuster, 2010), pp.490-492