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

Summary & key facts

Researchers reviewed many studies to see if 'forest bathing'—spending time in a forest and breathing the air—changes levels of cortisol, a hormone people use to measure short-term stress. They looked through almost 1,000 papers, included 22 studies in the review and 8 in a pooled analysis. Most studies found that cortisol went down after people spent time in forests compared with urban groups or compared with their own levels before the visit. The pooled results showed small but statistically reliable reductions in saliva cortisol for forest groups, but the effects were short-term, the available data were limited, and expectations or placebo effects may have helped produce some of the change.

Key facts:

• The authors searched major medical and science databases and screened about 971 articles to find relevant studies on forest bathing and cortisol.
• They included 22 studies in the full review and combined results from 8 studies in a quantitative meta-analysis.
• Most studies reported that cortisol levels were lower after people spent time in a forest compared with control or urban groups, or that individuals’ cortisol fell after a forest visit.
• When the researchers pooled saliva measurements, people in forest groups had about 0.08 micrograms per deciliter lower cortisol than urban groups before the visit, and about 0.05 micrograms per deciliter lower after the visit; these differences were statistically significant.
• The review says the cortisol changes appear to be short-term and that expected effects (sometimes called placebo effects) could be an important part of the result.
• The authors recommend more research because there were only a limited number of high-quality studies available, so we should be cautious about strong conclusions.

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