Two Minutes of Fear

It's sad and frightening watching paranoia running amok. Even if it's just for a moment or two. What do you say to a person who's convinced that others are out to taunt him? It's unlikely that any words will change the thought process. The person has already spent too many hours arriving at this point of suspicion. Too many hours spent processing in lonely thoughts, what is viewed and interpreted as intentional slights and attacks. What if the next time he doesn't snap out of it by your changing of the subject? How do you respond to that when you're the person that the paranoia is revealed to?