Sitting in Nature for Just 20 Minutes Per Day Cuts Stress Hormone Levels

Feeling as if we have come into contact with nature for at least 20 minutes could lower levels of stress hormones, according to scientists.

The authors of a study published in the journal Frontiers in Psychology wanted to answer whether experiencing nature, or taking what is dubbed as a "nature pill," would lower the levels of chemicals in the body associated with stress.

The researchers recruited 36 people who lived in cities, and asked them to spend time in an outdoor space that made them feel like they were interacting with nature three times a week for at least 10 minutes. They did this for a total of eight weeks. The participants were free to choose when and where this happened. Four times during the study, the subjects gave samples of their saliva before and after their nature experience.

Participants were asked to not engage in activities that could make them stressed while taking their nature pills, including going out at night, exercising, using their phones, having conversations, or reading.

Levels of cortisol in the participants' saliva dropped by 21.3 percent per hour on average after they had a nature experience.

The effect was most pronounced for stints outdoors of between 20 to 30 minutes. At that point, the participants still benefited but at a slower rate. Activity didn't seem to make a difference to cortisol levels.

A 28 percent per hour drop in the alpha-amylase enzyme was also noted in those who were least active and sat down, or sat and did a little walking.

The benefits of interacting with nature are already promoted by organizations like the Mood Walks program in Canada and the Nature Sacred program in the U.S. Meanwhile, The American Heart Association recommends getting outdoors to relieve stress and anxiety.

The researchers hope their study will help healthcare to accurately prescribe nature pills as a preventative measure and treatment for mental disorders.

Dr. MaryCarol Hunter, lead author of the study and associate professor at the University of Michigan, commented: "We know that spending time in nature reduces stress, but until now it was unclear how much is enough, how often to do it, or even what kind of nature experience will benefit us.

"Our study shows that for the greatest payoff, in terms of efficiently lowering levels of the stress hormone cortisol, you should spend 20 to 30 minutes sitting or walking in a place that provides you with a sense of nature."

Allowing the participants to choose when and where they took a nature pill helped the team to pinpoint the optimal time spent in the outdoors and in a way that could fit into modern life, said Hunter.

"Healthcare practitioners can use our results as an evidence-based rule of thumb on what to put in a nature-pill prescription," she said.