The Huffington Post has an interesting piece on how getting down and dirty with nature in, for example, a vegetable garden can keep us emotionally healthy.
The microbes in dirt, apparently, affect the same neurons that are stimulated by Prozac. A British study from a couple of years ago found that lung cancer patients exposed to the common, safe microbe Mycobacterium vaccae reported an increased quality of life, including a brighter mood.
According to the research, just rooting around in a vegetable garden or eating veggies picked from that garden would achieve the Prozac-like effect. And if you don’t have a vegetable patch, you can always try getting your hands dirty on your windowsill.