Horticultural therapists starting a new program may want to bring scientific evidence to the table to convince skeptical decision makers. Fortunately an increasing number of researchers around the world have been trying to prove how and why nature, physical exercise and gardening are good for the brain. Here are a few recent examples (beware, access to the original studies often require a fee). For more scientific studies, you can turn to Google Scholar, using pertinent keywords and setting the search for recent publications. There is even a handy alert feature that will help you track new research.
In the UK, allotment gardeners are in a good mood
Allotment gardens are the equivalent of community gardens in the US. This 2015 study out of the University of Westminster and the University of Essex compared 36 allotment gardeners before and after they spent time in their garden with 133 non-gardeners. The results are in: allotment gardeners had a significantly better self-esteem, total mood disturbance and general health than the non-gardening control group. Hence the researchers’ conclusion that “Allotment gardening can play a key role in promoting mental well-being and could be used as a preventive health measure.”
Physical activity boosts cognitive functions
This mainstream article points to several interesting studies linking exercise and improved cognitive abilities. One study out of Canada found that “Exercise triggers the production of a protein called brain-derived neurotrophic factor, or BDNF, which helps support the growth of existing brain cells and the development of new ones. With age, BDNF levels fall; this decline is one reason brain function deteriorates in the elderly. Certain types of exercise, namely aerobic, are thought to counteract these age-related drops in BDNF and can restore young levels of BDNF in the age brain.” Another study conducted by the University of Kansas Alzheimer’s Disease Center also concluded that exercise, such as a brisk walk for 20-25 minutes several times a week, could lead to cognitive improvements. While gardening is not an aerobic activity, the news is heartening.
The friendly soil bacteria
Back in 2007, there was much talk about a study that showed that the bacteria Mycobacterium vaccae, commonly found in soil, altered behavior of mice in a way similar to the effect produced by antidepressant drugs. Chris Lowry, the lead researcher on the study, then from Bristol University and now from the University of Colorado, Boulder, wrote “These studies help us understand how the body communicates with the brain and why a healthy immune system is important for maintaining mental health. They also leave us wondering if we shouldn’t all be spending more time playing in the dirt.” In 2013, two other researchers established that mice treated with Mycobacterium vaccae were able to run a maze faster than a control group, with decreased anxiety-related behavior. What are researchers waiting for to do studies on humans?
Our brain on nature
This beautifully written National Geographic article quotes several researchers who are convinced that nature’s main effect on the human brain is to lower stress. One set of studies found that urban folks who live near green space are better off in all kinds of ways. After mapping where 10 000 city dwellers had lived over 18 years, British researchers were able to state that those living near green space reported less mental distress. The same result was found in the Netherlands (people living within a half mile of green space were less prone to 15 diseases including depression, anxiety, heart disease, diabetes and asthma) and in Canada (out of 31,000 inhabitants of Toronto, those who lived on blocks with more trees “showed a boost in heart and metabolic health equivalent to what one would experience from a $20,000 gain in income”).