I've always wondered why I felt so much better after digging in the garden. I'd always assumed that it was simply because I was getting out and doing something I loved. But it seems that there are other explanations out there.
http://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/antidepressant-microbes-soil.htm
http://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/antidepressant-microbes-soil.htm