Effects of forest bathing (shinrin-yoku) on levels of cortisol as a stress biomarker: a systematic review and meta-analysis

Summary & key facts

This review looked at studies that measured cortisol (a stress hormone) after people visited forests, a practice called forest bathing or shinrin-yoku. The authors found that people in forest groups had lower salivary cortisol than people in urban groups, both before and after the visits. The reviewers say the change is a short-term effect and that placebo or expectation effects might matter. They also say more research is needed because only a small number of studies were available.

Key facts:

• The review screened 971 articles and included 22 studies in the systematic review and 8 studies in the meta-analysis.
• The meta-analysis reported salivary cortisol was lower in forest groups than urban groups before the intervention: mean difference (MD) = -0.08 μg/dl (95% CI -0.11 to -0.05); p < 0.01; I² = 46%.
• After the intervention, salivary cortisol was also lower in forest groups: MD = -0.05 μg/dl (95% CI -0.06 to -0.04); p < 0.01; I² = 88%.
• In all but two of the included studies, cortisol levels were significantly lower after the forest intervention compared with control or compared to pre-intervention levels in the forest groups.
• The authors noted that anticipated placebo effects (people expecting to feel better) could play an important role in the observed cortisol changes.
• The paper concludes that forest bathing can influence cortisol levels in the short term, but it calls for further research because the available data are limited.

Topics

Acupuncture Treatment Research Studies Biofield Effects and Biophysics Stress Responses and Cortisol

Categories

Health Sciences Medicine Physiology

Tags

Alternative medicine Bathing Biochemistry Biology Biomarker Cochrane Library Internal medicine Medicine MEDLINE Meta-analysis Pathology Placebo