Why would you assume being gifted with the ability to sense the otherworldly presence of the spirit world? This is a psychic gift and not a mental illness, though I can see why most of the people without this perceptive gift would say otherwise. It's been thought that all young minds are open and perceptive to the spirit world, but gradually shut it off because they believe it to be a product of imagination or insanity due to the adults in their lives saying so. They want to be loved and accepted by their adult peers so they in turn force themselves to believe in what the adult minds do.