"I think mentally ill people have enough trouble in their minds without having the Devil and God in there" - psychiatric nurse in relation to Peter Sutcliffe, the Yorkshire Ripper.
THE ARGUMENT
If religion is a mental illness then it needs stopping. You may say it is up to the professionals to decide if any follower needs professional psychological help but nobody can escape noticing that religious faith is functionally insane if not an actual mental illness. We know sane people who say the most insane things.
Suppose for the purpose of argument it is a mental illness.
That demands that it be treated by outspokenness in the hope that the person will grow out of it. People think we want them medicated or hospitalised. We want some to get that treatment but for most a straight-taking is enough. Be careful to listen. Mental illness and being to blame for what you do for the religion are compatible. This combination describes most religious people.
If you care about people then admit that if religion is not a mental illness it remains true that it harms the mental health of innocent people and even bad people.
You have no right to blame mental illness for the religious aspects of a person's mental illness. You cannot know exactly what the illness is doing but that does not give you the right to protect religion by simply just absolving it. The person in front of you is what matters not the religion.
_____________________
The evidence that religion is good for you is too open to interpretation and why is there not more and better evidence?
1 Most religion has not been good for animals or people - eg widow burnings, animal sacrifice etc
2 Any group that brings people together will report better mental health for the participants - religion is not necessary
3 Religion is a faith community but studies ignore the effects of faith
4 It is reasonable to hold that beliefs such as that God uses evil to fix you, that his son died for your sins so you murdered him and that family ties will not exist in Heaven are damaging. If they are not then that is strange but it does not change the fact that the beliefs are as good as trying to harm.
5 It is not just about people in a religious community - what negative effects hit people who are not members? For example, religion imposes its beliefs on society and schools and governments. If a belief contains reasonable danger and we have seen examples in a way it does not matter if it is imposed or not. It is bad. Bad belief posing as good is a way of imposing. Good beliefs do not need imposing. Religion imposes a duty on critics and those outside its fold not to admit or see that the doctrines have a power to harm or degrade. That is why we must rebel.
6 The evidence in favour of religious benefit is never that strong and there is a lot of grey so good today means bad tomorrow.
If religion becomes classified as a mental illness by the World Health Organisation (WHO) it will be the more extreme and dysfunctional forms of devotion that will end up on the list. In 2019, religious fanaticism nearly made it on. What is holding it back is that few want to be helped with their disorder. It is complicated when they have children. Pragmatism is needed before the classification can happen and we are not there yet.
Some argue that mental illness creates religion in the first place. That does not necessarily mean you are unwell in the head if you believe. But you are in an unsafe position. Some say you are.
Many say that it depends - if religious faith is too devout and starts ignoring important facts then it is a disorder. For example, some Christians and Muslims read violent nasty scripture texts as speaking only of peace - that needs to be seen for what it is: a form of psychosis. It is excellent and infallible evidence of mental illness unless they are being dishonest.
If sincere religion is not a mental illness, does that matter if it attracts people with mental illness? Certainly it does matter! Only a bad thing can draw in disturbed people.