Tree Therapy? ‘Forest Bathers’ Say It Helps
On a trek through a snowy western mountain range, a forest guide points to a grove of evergreen Japanese red cedar trees, and hikers gather around to take deep breaths.
They call themselves forest bathers, part of a growing movement that believes immersing oneself in nature and in the chemicals plants and trees emit has unexpected medical benefits. The trip is part of their orientation as new employees of a maker of power devices.
“Even if you can’t smell them, they are there,” the guide, Kazuhiro Kouriki, says of phytoncides, or chemicals emitted by some plants to protect themselves from insects and germs. Studies suggest that taking in the air around certain kinds of trees lowers stress and increases focus, Mr. Kouriki says.
The research isn’t definitive, but from Japan to Hollywood, forest bathers swear by the therapeutic effects of trees. Justin Bieber is a fan, posting photos of himself on Instagram enjoying nature. Gwyneth Paltrow recommended it in her newsletter, and some resorts in the U.S. have started to offer forest-bathing programs.
Japan’s government has spent millions of dollars promoting forest bathing, a term translated from the Japanese shinrinyoku, and it funds research into the possible benefits. Some 62 forests and wooded paths have passed a gauntlet of tests to be designated therapeutic by the Forest Therapy Society, a Tokyo-based nonprofit.
Local authorities sometimes organize checkups by medical doctors under a canopy of cedars, while companies send new employees into the woods for a therapeutic stroll ahead of the grinding workload new hires here face.
“At any company, people feel stress and we thought perhaps we could keep our new recruits better and longer if we gave them the opportunity to learn what stress is and how to cope with it,” says Chieko Uchiyama, a personnel manager at TDK-Lambda, the TDK Corp. unit that organized the recent mountain trip.
Scientists studying forest bathing focus on the compounds trees emit. They reason that if swallowing certain plants can have medicinal effects—aspirin, for example, is derived from a substance in willow bark—breathing in the compounds may similarly be therapeutic.
A study published last year by Qing Li of Nippon Medical School in Tokyo had a group of 19 middle-aged men walk through an urban area in Tokyo and, a week later, take a forest walk. The men had higher levels of a fat-burning hormone after the walk in the forest.
Earlier studies, including one published in 2008 in the Journal of Biological Regulators and Homeostatic Agents, analyzed findings of forest bathing from 13 female nurses between ages 25 and 43. It showed exposure to phytoncides increased the activity of antimicrobial proteins released by killer cells of the immune system. That could have implications for research into anticancer proteins, Dr. Li says, although little follow-up has been done. In 2018, he will embark on a multi-year study to measure the effect of forest bathing on high blood pressure and mild depression.
“My goal is to get it listed as therapy, so it can be prescribed,” Dr. Li says.
For his studies, he has struggled to recruit subjects who are willing to travel several hours from Tokyo and have their blood taken after some time in the mountains. Local volunteers take regular walks in the forest or have some exposure, so the results “are not as dramatic,” he says.
Some believe forest bathing was imported to Japan from Europe and adopted by the government in the 1980s, while others trace the practice to Japan’s native Shinto religion, which advocates communing with nature.
In Yoshifumi Miyazaki’s office at the environmental-science department of Chiba University near Tokyo, a photo shows him speaking with the Crown Prince Naruhito and Princess Masako. The heir to the Japanese throne and his wife stopped by the university last year for a presentation on the physiological effects of flowers, forests and trees, in particular the hinoki, a Japanese cypress.
For more than a decade, Dr. Miyazaki has studied measures like heart-rate and cortisol levels to determine whether breathing in compounds from hinoki oil can affect stress. His most recent research looks at how to reduce stress in wheelchair-bound seniors in need of rehabilitation so they can do physical therapy better.
He says he wants to recreate the outdoors for people too old or sick to venture out. “It will be a way to raise the quality of life,” says Dr. Miyazaki, whose business card is printed on a sliver of hinoki.
Back in the mountains, Tsubasa Funanami, a 22-year-old TDK-Lambda new employee, looks up at the 60-foot-tall trees and takes several deep breaths. Before the trip, he had questioned whether there was much point in forest bathing, but now he stares at the cluster of cedars and smiles.
Mr. Kouriki, the guide, then leads the forest bathers to the shore of Lake Nojiri. He pulls out a stethoscope and invites the trekkers to take turns listening to underwater sound. Mr. Funanami places the stethoscope’s chestpiece against a rock submerged in the lake and listens. “I’ve never been there but it sounds like space,” he says. Moments later, seated on a rock and staring out at the lake, he adds: “I feel like time is flowing slower than usual.”