Religion as a mental illness

[brewer]

I agree. Look at different societies and human killing, i.e. head hunting.

I disagree that they are interchangeable.  Mental illness is from chemical imbalances that may be congenital, aging, disease or a variety of other causes affecting the physiology of the body.  Delusions, on the other hand, are simply mental interpretations and these can vary from culture to culture.  There can be a combination of both, but delusions are a 'belief system' whereas mentally ill is a malfunctioning body.

I'm not sure what you consider not interchangeable. Not all mental illnesses in our society are necessarily the result of neurochemical imbalances. Please see my response to Cephus. Then we can continue the discussion if you like.