“Effects of Public Green Space on Acute Psychophysiological Stress Response: A Systematic Review and Meta-Analysis of the Experimental and Quasi-Experimental Evidence”, 2019-09-09 (; backlinks):
Contact with nature is widely considered to ameliorate psychological stress, but the empirical support for a causal link is limited. We conducted a systematic review to synthesize and critically assess the evidence.
6 electronic databases were searched. 20-six studies evaluated the difference between the effect of natural environments and that of a suitable control on the acute psychophysiological stress response. 18 studies were rated as being of moderate quality, 4 studies of low quality, and 4 studies of high quality.
Meta-analyses indicated that seated relaxation (g = 0.5, p = 0.06) and walking (g = 0.3, p = 0.02) in natural environments enhanced heart rate variability more than the same activities in control conditions. Cortisol concentration measures were inconsistent.
While intuitively and theoretically sound, the empirical support for acute stress-reducing effects of immersion in natural environments is tentative due to small sample sizes and methodological weaknesses in the studies. We provide guidelines for future research.