If/when a person is not in control of their own mind such as those who have been ‘programmed’ as in what happens to those in cults, that is a mental illness. Mental illnesses may be cured, particularly this type, as people can be ‘deprogrammed’. This is the type of mental illness that happens to those who are religious. Also, the term ‘religion’ has been associated with too narrow a view. In reality, religion is simply irrational belief. That can take many forms; not just as with organized religion or cults. Virtually anything can become as a religion to some people. It is what causes a negative change in an otherwise normal mind that actually constitutes ‘religion’/irrational belief. That could be a component part of religion (or several parts), such as belief in a synthesized ideological concept, like the idea of a soul, Hell, an afterlife, a God/gods, a Devil, or even Evil. Evil does not exist in nature or the natural world, it is an invention made real by belief in it.