Bad moods are contagious and can spread through friends and family across hundreds of miles, according to new research.

How grumpy people feel can be influenced not only by the state of mind of those closest to us, but also by friends of friends that we have never met like ripples from "pebbles thrown into a pond" , claim scientists.

http://www.telegraph.co.uk/news/newstopics/howaboutthat/4031530/Moods-spread-like-ripples-through-friends-say-scientists.html