Forest Bathing: Making a splash in preventative health

by Mary Hall on February 22, 2013

If you’ve ever been on a long wilderness trip, you know what it feels like by the end of the first week. Miles from civilization and seven days from your last hot shower, your thoughts may periodically (or obsessively) turn to bathing.  It’s easy to imagine steam rising from a bathtub just beyond the next hill . . . your favorite soap, a towel, and freshly laundered jeans dangling from a tree nearby.  Alas, this particular style of forest bathing is hard to come by.

Fortunately, a simpler style is widely available and gaining increasing attention from researchers in preventative health.

It may not get you clean, but “forest bathing” (or Shinrin-yoku, as it’s called in Japan) offers an impressive array of health benefits.  Chief among them is its ability to reduce stress.  As little as twenty minutes of “taking in the forest atmosphere” (in other words, simply being in the woods . . . ) has been shown to significantly lower levels of cortisol in the bloodstream. Some researchers have gone so far as to suggest that regular forest bathing may offer protection against cancer, depression, and dementia as well.

We’ll focus on the most compelling evidence, which is that a brief stroll in the forest . . . in some cases, merely gazing at a forest . . . can significantly lower your level of cortisol.

What’s cortisol?   It’s the primary hormone your body produces when you’re under stress.  Cortisol is often referred to as the “fight-or-flight” hormone–for good reason.  Imagine you’re one of the earliest humans on earth.  You’re wandering around a meadow blithely swatting at insects while you gather nuts and berries.  Suddenly, you hear hoof beats and notice a wild boar charging at you!  The instant you see the boar . . . before you consciously recognize the danger . . .  your adrenal glands are releasing stress hormones into your bloodstream.  Two of these hormones, adrenaline and cortisol, prepare you to either (a) fight the wild boar or (b) run from it.    Adrenaline boosts your breathing rate, heart rate, and blood pressure.  Cortisol boosts your blood sugar. All of this gives you energy.  Now you can run!!!!!

While you’re running . . . cortisol is prolonging these immediately helpful effects while suppressing longer term body functions.  For example, cortisol alters your immune system and suppresses your digestive system, reproductive system, and growth processes.

Fast forward to today. Instead of a boar, you’ve got a deadline for a blog bearing down on you.  Before you can tackle that stressor, you have to navigate rush hour traffic while a family member turns up the volume on the radio so he can hear it comfortably above the high-pitched screeching your car has just starting to emit.  As the number of stressors climbs, a well-meaning-yet-primitive part of your brain has been signaling your faithful adrenal glands to release stress hormones so that you can either (a) fight the wild blog, your son, and the car, or (b) flee from them.

Chances are you’ll neither fight nor flee.  If your natural disposition is fairly laid back, your cortisol levels will return to normal once the stressors are removed (in this case, parked the car, finished your blog, and settled into your easy chair).  If you’re more sensitive to stress or you find it difficult to relax, your cortisol levels may stay elevated far after the stressors are removed.   In this case, cortisol is not doing you any good.  In fact, it’s probably harming you.

According to experts at the Mayo Clinic, overexposure to cortisol and other stress hormones puts you at increased risk for a number of health problems, including:

  • Heart disease,
  • Sleep disorders,
  • Digestive problems,
  • Memory impairment,
  • Depression, and
  • Obesity

Photo by Derek Gavey on Flickr


In her article, Take Two Hours of Pine Forest and Call Me in the Morning, Florence Williams describes Japan’s enthusiasm for research on forest-bathing .  The Japanese government has funded more than $4 million in forest-bathing research since 2004.  As a result, Japanese scientists are leading world efforts to discover how green spaces affect us on a molecular level.  At this time, Japan has 48 Forest Therapy trails officially designated for “forest bathing”; within the next 10 years, 52 more trails will be added.  In small lodges along these trails, the study of forest-bathing continues.

One of the most comprehensive studies of forest-bathing involved experiments with 280 participants in 24 forests across Japan.  Participants took turns viewing or walking in both forest areas and city areas.  Each session was limited to approximately 15 minutes.  At baseline, and before and after each session, researchers measured each participant’s cortisol level, blood pressure, and heart rate.  The results indicated that forest landscapes significantly lowered cortisol levels, heart rates, and blood pressure –whether the participants walked within these settings or simply viewed them. Earlier research had shown that stress indicators were lowered somewhat by simply viewing images of forest landscapes while indoors.

How can a forest have such a profound effect on our stress levels?  Japanese researchers believe we’re actually designed to live in forests and other natural areas. Humans lived in forest environments for almost 5 million years. We’ve been living in cities for less than two thousand years.

Japan is not alone in recognizing the health benefits of natural environments.  In 2009, researchers at the University of Illinois found children with attention deficit hyperactivity disorder (ADHD) concentrated better after a 20-minute walk in a natural area (compared to a similar walk in an urban setting). They concluded that “doses of nature” might serve as a safe, inexpensive, and widely accessible tool for managing ADHD symptoms.

“Thousands of tired, nerve-shaken, over-civilized people are beginning to find out that going to the mountains is going home; that wildness is a necessity; and that mountain parks and reservations are useful  . . . as fountains of life.”

—John Muir, from Our National Parks, published in 1901

As public health researchers continue to explore the importance of natural areas, our world is becoming increasingly urbanized.  In 2010, the percentage of people living in urban areas was nearly 70% for Japan and more than 80% for the U.S.   It’s estimated that all of the world’s population may be living in urban areas within the next 50 years.

If that estimate stresses you out, here’s what you can do to make yourself feel better:  First, go out and take a small walk in the woods.  Second, do what you can to to preserve natural areas. Third, continue walking in the areas you’ve helped to preserve.


Park BJ, Tsunetsugu Y, Kasetani T, Kagawa T, Miyazaki Y. 2010. The physiological effects of Shinrin-yoku (taking in the forest atmosphere or forest bathing): evidence from field experiments in 24 forests across Japan. Environ Health Prev Med. 15(1):18-26. doi: 10.1007/s12199-009-0086-9.

Talyor AF, Kuo FE. 2009. Children With Attention Deficits Concentrate Better After Walk in the Park.  Journal of Attention Disorders; 12(5) 402-409. doi: 10.1177/1087054708323000

Williams, F. December 2012. Take Two Hours of Pine Forest and Call Me in the Morning . Outside Magazine.