but, trying to set the issue up as religion v mental health is also missing the point.
i actually think that scientology makes a kind of deep observation in it's cynicism about the relationship between religion and mental health: religion is dangerous precisely because it exploits those of poor mental health. it's a control mechanism, after all. the difference is that the christian church has evolved from an instrument of conquest, as it certainly was, into a capitalist institution that seeks to use it's control to exploit the vulnerable into raising capital, while the muslim church remains an instrument of conquest for an elite in the arabian peninsula, who continue to spread the ideology in order to dominate resources.
that's what you can't separate: religion and mental health. religion requires a disaffected population, or disaffected members of a population, in order to thrive. and, those disaffected members of the population seek out religion as an escape from reality.
http://www.cbc.ca/news/canada/montreal/quebec-flint-couillard-muslisms-1.4173300