‘Kashf’ is not some kind of sickness rather it is a portion of one of the quality perfection in a human being. When a person is able to concentrate completely without any distraction sometimes certain things are revealed to him. We don’t understand how you understood ‘Kashf’ to be a sickness.
There is a possibility that those people who are afflicted with mental problems, due to their immense concentration on something, are also able to see stuff that is not usually seen. So, ‘Kashf’ could also happened to mentally retarded people as it happens to sane pious people. Maybe this is what you are trying to say.