In a recent paper in the Quarterly Journal of Economics, Filipe Campante and David Yanagizawa-Drott look at the affect of religion on economic growth and happiness. They look at observance of Ramadan fasting and exploit variation in the length of daily fasting due to the interaction of the Islamic calendar and a country's latitude. They find that longer Ramadan fasting has a negative effect on output growth in Muslim countries, but that longer Ramadan fasting increases subjective well-being. In other words, some religious practices may make the individual feel better, but may be bad for the overall economy.
For me, this paper raises several interesting questions for economists. First, do all religious practices have this effect? For example, Sabbath or Holy day observance. Second, can religion positively affect both economic growth and happiness? Third, might there be differences amongst religions - with some having no effect, others negative-positive, others negative-negative or positive-positive?