Different studies show wildly different results on whether walking in the woods lowers stress hormones—sometimes it does, sometimes it doesn’t—and that’s probably because things like how long you stay, what time of year, or even what you expect to happen are messing with the results.

A meta-analysis of all available randomized controlled trials on forest bathing and cortisol, with subgroup analyses by duration (<30 min, 30–60 min, >60 min), season (spring/summer vs. fall/winter), forest type (coniferous vs. deciduous), participant age group (young, middle-aged, elderly), and baseline stress levels, using meta-regression to quantify the contribution of each unmeasured factor to heterogeneity (I² = 88%).

A multi-site observational study across 15 different forest types and seasons, measuring cortisol in participants before and after a standardized 60-minute forest walk, while recording participant demographics, prior nature exposure, and self-reported expectations, to test whether variation in cortisol response correlates with these factors.

A randomized trial where participants are assigned to either a real forest walk or a simulated forest environment (e.g., indoor VR forest with audio), with half of each group told the activity will 'significantly reduce stress' and half told it has 'no known effect', to isolate the impact of placebo expectations on cortisol response.

A retrospective analysis comparing individuals who showed large cortisol reductions after forest bathing (top 25%) with those showing no change or increases (bottom 25%), examining differences in prior nature exposure, season of visit, forest type, and baseline psychological traits.

A pilot study at one forest site measuring cortisol in 30 participants across four different seasons, with each participant visiting at different times of day and under varying weather conditions, to assess whether within-person cortisol variation correlates with environmental factors.