my reply is nowhere as detailed as the previous i tend to remember the the quote 'the mystic and the madman are swimming in the same sea its the mystic who can came back at will. 'i suffere chronic depression with bouts of severe episodes on top i have also heard voices been deluded and dissociative states whilst severely depressed i have also many years of practicing meditation zen and other forms.i have never had an enlightenment experience ,-states of calm and peace along with turmoil ,i now no longer do it but i may do so in the future.I know many people who practise meditation who to my observation appear to be slightly off the wall. i know one person who has done zen for many years who i would now say has episodic psychotic episodes ,would he have had them with or without zen thats impossible to answer,it strikes me that vulnerable people who are seeking when doing meditation can allow unconcious material through and disturb their mental states i imagine these people need people who have learnt from these experiences and come out the other side to guide them along the road .there is a line of thought also that people can become possessed by both good and bad entities whilst in altered states -not sure about that but who knows?