How Gardening Positively Impacts Your Mental Health

Lauren Stables

Have you ever wondered why we often yearn to be outside in our garden, even if it is just to pull a few weeds? How would you describe your mood when you're working in the soil? I would describe myself in my garden as focused, at ease and relaxed—it is easy to lose track of time! Believe it or not, there is some fascinating evidence that shows that interacting with soil in your garden has powerful mental health benefits. Scientists have discovered a strain of bacteria in soil, Mycobacterium vaccae, that could be responsible for the effects we feel after a day out in the garden. 

You see, this isn't a specific bacterium only found in a certain garden in a certain remote location that we would be lucky to find. This bacterium is a nonpathogenic species of the Mycobacteriaceae family of bacteria that naturally lives in all soils, which means if you have non-sterilized soil in your garden, it is probably lingering there too! This strain of bacteria is especially powerful when we interact with it because it has the power to trigger the release of serotonin in the brain. Effects of the brain releasing serotonin range from elevated mood to a decrease in anxiety. 

In addition to the release of serotonin, Mycobacterium vaccae has also been documented to increase and improve cognitive function. So while your hands are busy working to benefit the soil, the soil is busy benefiting you!

In the past 10 years there have been several individuals who have explored the link between Mycobacterium vaccae and its effects on the brain, including Dr. Mary O’ Brien from Royal Marsden Hospital in London, Dr. Chris Lowry of Bristol University, and a dedicated research team at Sage College in Troy, New York.

Dr. Mary O’ Brien explored the benefits of the bacteria while working as an oncologist, through experimental treatments with lung cancer patients. She discovered that when she inoculated the patients with the bacteria, they had a broad spectrum of positive responses. She observed that after the treatment patients had a lower occurrence of some cancer symptoms, but also had an increase in emotional health and cognitive function—overall decreasing the emotional toll of the painful disease.

Colonies of M. vaccae grown on agar.  Credit: Laura Rosa Brunet, UCL

Dr. Chris Lowry of Bristol University was impressed by these findings in Dr. O’Brien’s published paper. He went on to expand the research by focusing on the link between Mycobacterium vaccae and serotonin production, which he explored through stress-inducing tests with mice. Some of the experiments that stood out included injecting the mice with the bacteria before putting them through a behavioral stress test that included swimming. He noticed that not only were the mice less stressed during the test and after, but that they didn’t seem to mind even the swim. He measured the stress response and the serotonin release of those mice by testing their cytokine levels. Cytokine is a part of the chain reaction that produces that powerful chemical serotonin. He discovered that the mice injected with the bacterium prior to the behavioral stress test had higher cytokine levels than the control group.

The researchers at Sage College in Troy, New York, wanted to focus their efforts on the impact Mycobacterium vaccae has on cognitive function. This team also turned to mice to test their theories, choosing the iconic experiment of placing a mouse in a maze. The research team compared the cognitive performance of a control group of mice versus those who had ingested Mycobacterium vaccae. The mice that ingested the bacterium were observed completing the maze twice as fast as those in the control group. They were also observed demonstrating half as many behaviors associated with anxiety as those in the control group. After the experiment concluded, the bacterium was removed from the mice’s diets; however, the mice who initially ingested the bacterium continued to perform better than the control group for up to three weeks.

I invite you to explore the expanding research of soil and its health benefits on us, as the areas highlighted in this blog are just the tip of the iceberg. Imagine how this type of research might affect gardening communities and how it might support those seeking garden programs for their own communities, schools and places of worship in a world that often says “Prove it.” Turns out the proof was in the soil and under our fingernails the whole time.

Resources

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Schlanger, Z. (2017, May 30). Dirt has a microbiome, and it may double as an antidepressant. Retrieved January 08, 2018, from https://qz.com/993258/dirt-has-a-microbiome-and-it-may-double-as-an-antidepressant/

University of Bristol. (2007, April 10). Getting Dirty May Lift Your Mood. ScienceDaily. Retrieved December 7, 2017 from www.sciencedaily.com/releases/2007/04/070402102001.htm

“Getting Dirty May Lift Your Mood.” Bristol University: Medical News Today. 2007-04-05.

“Dirt exposure ‘boosts happiness,'” BBC News, 2007-04-01.