GxE.

Here's a fascinating article about a possible link between a specific gene set and the tendency toward post-traumatic depression. The article goes on to describe a new field of science which examines the "interplay between particular genes and environment", known as GxE. Brilliant stuff. It's about time science began to fully assimilate the fact that there's more to the story than just a string of isolated circumstances.

Thanks to Katherine for this one.