"Circumstances predict religiousness," he said. "Difficult circumstances lead more strongly to people being religious. And in religious societies and in difficult circumstances, religious people are happier than nonreligious people. But in nonreligious societies or more benign societies where many people's needs are met, religious people aren't happier -- everyone's happier."This should settle the discussion on religiousness and happiness. Irreligious people has a harder time in religious countries, but if irreligious people are the majority, then everyone's better off. The map in this post (which I think is from the Gallup poll this study is based on) is also pretty self-explanatory.
ScienceDaily Aug. 8, 2011