Potential preventive effects of forest bathing/Shinrin-yoku on depressive symptoms: a narrative review of mechanistic evidence.

Depression affects more than 280 million people worldwide and remains a major public health challenge, with limited universally effective preventive strategies. Non-pharmacological interventions have gained increasing attention as complements or alternatives to pharmacotherapy. Shinrin-yoku (forest bathing), a Japanese health practice involving immersion in forest environments, has been reported to relieve stress, enhance immune function, and improve mood. This review synthesizes current evidence on the potential preventive effects of forest bathing on depressive symptoms and examines the mechanistic pathways underlying these effects. A structured search of major scientific databases identified studies investigating psychological responses, neuroendocrine and autonomic regulation, immune-inflammatory markers, and related physiological parameters. Across diverse populations, forest bathing consistently reduced negative mood states, improved vigor, and showed beneficial effects on anxiety, depressive symptoms, sleep quality, and stress biomarkers. Mechanistic evidence suggests that forest bathing may modulate the psycho-neuro-endocrino-immune network through improved sleep, reduced stress hormone levels, enhanced parasympathetic activation, and increases in circulating serotonin, oxytocin, and insulin-like growth factor-1, alongside reduced inflammatory markers. While existing findings are promising, most studies involve small samples, short-term interventions, and limited clinical populations. Future large-scale, controlled studies are needed to confirm long-term effects and to clarify whether forest bathing can contribute to prevention or adjunctive management of depressive symptoms.