MD, PhD, FMedSci, FRSB, FRCP, FRCPEd
Shinrin-yoku means “taking in the forest atmosphere” or “forest bathing.” It was developed in Japan during the 1980s and has, according to its proponents, become a cornerstone of preventive health care and healing in Japanese medicine. Researchers primarily in Japan and South Korea have established a robust body of scientific literature on the health benefits of spending time under the canopy of a living forest… there have been many scientific studies that are demonstrating the mechanisms behind the healing effects of simply being in wild and natural areas. (some of this research is available here). For example, many trees give off organic compounds that support our “NK” (natural killer) cells that are part of our immune system’s way of fighting cancer.

The claimed benefits of Shinrin-yoku are remarkable:

  • Boosted immune system functioning, with an increase in the count of the body’s Natural Killer (NK) cells.
  • Reduced blood pressure
  • Reduced stress
  • Improved mood
  • Increased ability to focus, even in children with ADHD
  • Accelerated recovery from surgery or illness
  • Increased energy level
  • Improved sleep
  • Deeper and clearer intuition
  • Increased flow of energy
  • Increased capacity to communicate with the land and its species
  • Increased flow of eros/life force
  • Deepening of friendships
  • Overall increase in sense of happiness

But is any of this really true?

The aim of this state-of-the-art review was to summarise empirical research conducted on the physiological and psychological effects of Shinrin-Yoku. Research published from 2007 to 2017 was considered. A total of 64 studies met the inclusion criteria. According to the authors, they show that health benefits associated with the immersion in nature continue to be currently researched. Longitudinal research, conducted worldwide, is needed to produce new evidence of the relationships associated with Shinrin-Yoku and clinical therapeutic effects. Nature therapy as a health-promotion method and potential universal health model is implicated for the reduction of reported modern-day “stress-state” and “technostress.”

Odd?

Yes!

A look at the primary studies reveals that they are usually small and of poor quality.

Perhaps a brand new  review aimed more specifically at evaluating preventive or therapeutic effects of Shinrin-Yoku on blood pressure can tell us more. The authors considered all published, randomized, controlled trials, cohort studies, and comparative studies that evaluated the effects of the forest environment on changes in systolic blood pressure. Twenty trials involving 732 participants were reviewed. Systolic and diastolic blood pressure of patients submitted to the forest environment was significantly lower than that of controls. The authors concluded that this systematic review shows a significant effect of Shinrin-yoku on reduction of blood pressure.

I find this paper odd as well:

  • it lacks important methodological detail;
  • the authors included not just controlled clinical trials but all sorts of ‘studies’;
  • there is no assessment of the methodological rigor of the primary trials (from what I could see, they were mostly too poor to draw any conclusions from them).

What does all of this mean?

I have no problems in assuming that relaxation in a forest is beneficial in many ways and a nice experience.

But why call this a therapy?

It is relaxation!

Why make so many unsubstantiated claims?

And why study it in such obviously flawed ways?

All this does, I fear, is giving science a bad name.

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