Theism is literally childish

[Whateverist]

Theism is a form of superstition more than mental illness, though it does feature heavily in the mental illness of religious individuals, to my knowledge.

I've always thought this too, that believers suffering through mental illness so often feel that their suffering is God's punishment.  It can result in a lot of obsessive rumination on what one has done to disappoint God and so on.  But I doubt if it is universally an extra burden.  There might even be a few who get comfort from their belief at such times, but if there are we never hear from them here.