It takes a wise or a professional person to do that. It is not easy to talk to someone who is in that condition cos you do not know the amount of damage it has caused him or her.
The best way is to put yourself in their shoes, and let them know that you clearly feel the same way. And also do all you can to make them feel safe where they are. Assure them of their safety first and then provide safety measures that they can use as a guide in the nearest future.