Interesting dividing line, I would characterise susceptibility to conspiracy theory alternative lifestyle cult type stuff as a type of mental illness, particularly when it leads to physical harm to a child.
Yes, @Heather37231 , those things may certainly appeal to someone with MH difficulties. But I dont see the two as inevitably related, more of a syllogistic link, ie unusual and dangerous beliefs appeals to a lot of people with MH issues have unusual and dangerous beliefs, but not everyone with unusual beliefs has a MH problem. These things are continuums surely, like anti vaxxers, etc etc.