Is religion a "controlled psychosis?" Scientist and author, Robert Sapolsky, takes on the matter in a fascinating essay/speech called "Belief and Biology." From the essay:
What I've just been considering is the superstructure of religion--the big building blocks: there are multiple deities, there is but one god and he is Allah, "I am who I am," any version of this--is an awful lot like schizotypalism. Who is it that invented the notion that virgins can give birth? Who is it who first came in with the extremely psychiatrically suspect report about hearing a voice in a burning bush? In most of the cases we don't know much about the psychiatric status of these folks. In the more recent historical cases, we certainly do, and schizotypalism is at the heart of non Western and Westernized large theological systems.
Now the second chunk of neuropsychiatry and religion I want to talk about is one that shifts to a different scale of what religion is about. Certainly a big chunk of religion is these big theological bits of superstructure that you build your whole belief system on. But what religion very often really is about is the daily behaviors. The daily rituals. Insofar as the devil is in the details, god is in the details too. It's in that realm where we can get insight into the roots of this aspect of religiosity: another neuropsychiatric disorder.
Full piece here.