Getting Dirty May Lift Your Mood

http://www.sciencedaily.com/releases/2007/04/070402102001.htm

Bacteria found in the soil activated a group of neurons that produce the brain chemical serotonin.

Treatment of mice with a 'friendly' bacteria, normally found in the soil, altered their behavior in a way similar to that produced by antidepressant drugs, reports research published in the latest issue of Neuroscience.