There is no evidence cited in the article suggest that religious belief is responsible for the effects. What you've quoted by Fotuhi is a belief that religious belief has those effects. Research has shown, however, that religious activities and "spirituality" have an effect. Koenig, one of the co-authors suggests that "people doing the types of things like religious people do -- socializing, doing similarly complex cognitive tasks, would have similar benefits." And that does seem to be the case, both with socializing, and with meditation (which arguably serves a function similar to prayer and/or "reading the bible").