Since ancient times, people have benefited from taking walks in the forest. In 1982, the Japanese Ministry of Agriculture, Forestry, and Fisheries came up with the technical term "shinrin-yoku," which translates to "forest bathing."
Experts say that forest bathing involves more than just walking through a natural environment. They define it as "making contact with the forest's atmosphere and taking in all of its associated sensations."
Most supporters of shinrin-yoku bring up the practice's ability to lower stress levels as its leading benefit. Some of them have also looked for other ways that it affects human health.
A 2017 study by Seoul National University indicated that forest therapy is a new and effective method for alleviating depression in adults. Other researchers investigated the potential application of the practice in preventing lung ailments and heart disease. (Related: 13 Lifestyle habits to practice if you want to live longer.)
Forest bathing is one of the ways that people benefit from the presence and proximity of green spaces. In recent years, researchers have been paying more attention to the psychological impacts of greenery.
For example, a 2011 study by the University of Exeter compared the mental effects of physical exercise in natural environments and similar workouts in indoor locations. They found that exercising in natural surroundings benefits the mental health of participants.
The Exeter study and other similar research showed that nature may have a positive effect on human mental well-being.
In their recent study, the Italian researchers sought to expand the details of how forest bathing affects stress levels. The University of Parma researcher Michelle Antonelli served as the author of the study.
Antonelli's team collected relevant studies for review and meta-analysis. They used cortisol levels to measure the stress of participants in the experiments.
Cortisol levels increase during stressful periods. The steroid hormone appears in saliva or serum, making it easy to measure its levels and evaluate the psychological stress of an individual at any time.
Starting with almost 1,000 articles, the researchers narrowed their targets down to 22 for the systematic review and eight for the meta-analysis. They released their findings in the scientific journal International Journal of Biometeorology.
In their meta-analysis, the Italian researchers set forest bathing as staying in a forest and absorbing its air for a specific amount of time. Applicable activities included walking, resting, and observing the environment.
Several studies used a control group that did not partake in forest bathing. Other experiments compared shinrin-yoku and other physical activity, like walking in an urban environment as opposed to a natural one.
The results showed that almost all of the studies reported a health benefit. Excepting two studies, they found considerably lower cortisol levels in forest bathers compared to their counterparts in the control or comparison groups.
Further, the Italian researchers spotted an anticipatory effect of forest bathing. Right before they began their session, participants already displayed reductions in cortisol levels.
In one evaluated study, the cortisol levels of participants went down as soon as they learned that they were going to the forest.
"Forest bathing is considered an anti-stress practice, and planning to visit a forest seems to positively influence cortisol levels, even before physically interacting with it,” Antonelli and his colleagues reported. “Therefore, watching a forest, and possibly even the sole mental visualization of a forest, may have a role in triggering anticipated placebo effects.”
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