Those of us who are obsessed gardeners can give a million reasons why we choose to be in the garden instead of almost anywhere else: the feel of the warm sun on our shoulders, the smell of digging into fresh soil, the satisfaction that comes from harvesting a salad or bouquet from our very own yard. But it seems that there may be a biochemical reason for our "addiction" as well.

Researchers at the University of Bristol and University College London found that a beneficial soil bacteria, Mycobacterium vaccae, activated a group of neurons that produce serotonin. Serotonin is a chemical that produces feelings of calm and happiness, and is produced by several foods and activities, including chocolate and aerobic exercise. Low levels of serotonin are often the suspected culprit in clinical depression.

In the study, which has been published in the latest issue of Neuroscience, mice who were treated with Mycobacterium vaccae altered their behavior much in the same way as mice who are treated with antidepressant drugs.

Again, science is proving what we already suspected: that the time we spend in our garden contributes more than just a pretty landscape and fresh produce for the table. It gives us an improved outlook on life, thanks to regular exercise that comes from digging, weeding, and mowing; the mood-lifting benefits of spending time in the fresh air and sunshine; and a happier disposition thanks to one of the many millions of denizens that inhabit our soil.

Photo by anitapatterson.