I have written a few posts on the relationship between religion and mental illness. A recent case illustrates that religion is, in fact, a mental illness and that it is only the sheer number of people who have been brainwashed that prevent it from being classified as such.
If only one person believed that he was immortal and that he had an invisible friend with infinite magic powers, then that person would clearly be suffering from a delusional form of insanity. Yet, if many people believe the same thing and call it religion, then they are not insane.
Obviously, the only difference between the two scenarios is the sheer number of potential mental patients. Why should that make a difference? Well, aside from the logistical difficulties of treating all these people as patients in need of institutionalization, the obvious reason is that they constitute a physical threat to the rest of us. In short, their implicit threat of the use of physical force (bullying) is the only reason they are running the asylum rather than in it.
The case of Elizabeth Smart's kidnapper proves my point. The crimes he committed occurred eight years ago now, but his case has yet to go to trial. Why? Because he declared himself the founder of a new religion and was institutionalized for insanity.
The manner in which the authorities treated him shows that they know this sort of thing is a form of insanity--as long as we aren't talking about the founders of their own religion.
The case also illustrates how modern notions of mental health can be misused by the religious to persecute members of competing religions just as they were used in the former Soviet Union to persecute those who didn't believe in the state religion: communism.
Whether or not a person's thoughts and notions constitute "insanity" depends on his religion. If he is a member of the majority religion, then he is sane. But, the same ideas espoused by a member of a religious minority will result in his classification as mentally ill.
This is yet more proof that, deep down, the religious know their beliefs are delusions. Other signs that they know this are 1. their disproportionate anger at and intolerance of dissenters, and 2. their need for frequent group reinforcement--because if "everybody" believes, then it can't be crazy. (As I mentioned before, this is the real reason they insist on organized school prayer and other government endorsement of their beliefs.)