This is a quick theory. We’ve confirmed that Miles was born on the island, and we see him looking at himself as a baby. I believe that he may have gone too close to himself, or he may get closer in the near future.
Remember what happened in the Orchid Out-take video at the 2007 Comic-Con? If you don’t you can watch the video here:
What that video establishes is that future versions or people/bunnies shouldn’t touch or get too close to past versions of people/bunnies. We don’t know what would happen. Perhaps the future version would die, perhaps the universe would explode. I think that the I believe that he got too close to himself and therefore screwed up his brain and let him talk to dead people. That’s that.