I spend a bit of time on atheist blogs, and something that comes up fairly often is equating religion with mental illness. And that is not ok.
I’m an atheist. I do not believe in any gods, or any higher power. We’re alone in this world, and only humanity can make humanity any better. No-one’s going to reach out a miraculous hand and heal me, or anyone else. I rely on the best science has to offer me in order to be well.
I believe religion is a delusion. It’s not grounded in logic, or science, or reality. But that doesn’t mean that religious people are mentally ill. Many people hold delusional ideas about the world without being mentally ill – it’s simply a process of social and cultural pressures that perpetuate false ideas.
Religion is a choice – you can choose to leave it at any time. There are complex social pressures that make it difficult, but it is possible, however difficult for some, to walk away from it. Mental illness does not have that element of choice. I cannot choose to not be mentally ill, no matter how much I wish I could.
Religion has a cure – deconversion. On leaving the church, you can let the old ideas go and make room for new ones. Mental illness does not have that luxury. There is no cure for what ails many of us. There is remission, which may even be permanent. There is management, learning to live with the hand you’ve been dealt. But there is no cure.
Comparing religion to mental illness hurts the mentally ill. We are made less by trying to include a group that is fundamentally different from us.
Drop Bear Exterminator 
I am Christian, but one of my closest friends is Atheist We don’t let our different beliefs come between us. 🙂
Anyway, I just wanted to say thanks for this post. I agree that religion is not a mental illness. And I agree that calling religion mental illness hurts people who are actually mentally ill.
My personal little opinion here is that religion itself isn’t a mental illness (for many of the very good reasons you describe) but the people that let it define their life – what most would call “fundies” or “zealots” – display a lot of the symptoms of various mental illnesses. Some of the more evangelical christians I’ve known can appear downright schizophrenic at times, up to and including visual and auditory hallucinations but normally stopping at the whole “redefining what happens in reality to fit their own worldview” part. And anything that can cause that as a result of being part of a societal group is harmful by definition.
So no, hyper-religious people are not mentally ill. But a lot of them have worked their minds into a delusional state that mimics it pretty well.
I’ve experienced the hallucinations of evangelical religion, and I believe that has more to do with the hyper-emotional state induced at evangelical events than any disorder of the mind. Mass hysteria is a crappy term, but it describes what happens in ‘revival meetings’ pretty accurately.