In most countries, religious people tend to be happier and less depressed, and it's often suggested that religion somehow provides a happiness boost and protects against depression.
Maybe, so the thought process goes, religious belief alone is enough to perk people up, but even if it doesn't then participating in religious gatherings, and the social support that goes with it - well surely that's got to help.
It's an attractive idea, but the problem is that it's really difficult to unpick cause and effect. Maybe it's simply that depressed people stop being religious. That's certainly what a study that came out last year suggested.