Abstract: Mental health issues among college students have become a significant challenge in higher education, with the pervasive stigma surrounding mental illness significantly undermining the effectiveness of traditional psychological interventions. Forest therapy, as an innovative approach combining nonpharmacological treatment with contactless intervention, effectively circumvents the interference of stigma associated with illness, demonstrating potential in alleviating psychological stress and promoting physical and mental well-being. This study developed a standardized forest therapy intervention protocol and employed a controlled experimental design. It introduced fractional exhaled nitric oxide (FeNO) as a stress-related biomarker to systematically analyze its stress-relieving mechanisms. Additionally, physiological indicators including peripheral oxygen saturation (SpO₂), heart rate (HR), systolic blood pressure (SBP), and diastolic blood pressure (DBP) were selected, while psychological indicators were validated using the Pittsburgh Sleep Quality Index (PSQI) scale and the tension (TEN), depression (DEP), and fatigue (FAT) dimensions from the Profile of Mood States (POMS) scale (The terms TEN, DEP, and FAT appearing in the following text are all indicators for assessing stress-related negative emotions). Experimental results reveal: (1) DBP significantly improved in all experimental groups, with heart rate trends inversely correlated between low-to-moderate stress and high-stress groups. Stress and depression scores decreased across all groups, with particularly marked improvements in the high-stress group. (2) The effects of forest therapy exhibit stress-level dependence: High-stress individuals achieve physical and mental improvements by suppressing hypothalamic–pituitary–adrenal (HPA) axis hyperactivity and synergizing attention restoration with stress reduction mechanisms; low-to-moderate stress individuals benefit more from cognitive restructuring and parasympathetic optimization. The high-stress group demonstrated a unique response pattern of “depression alleviation+elevated FeNO” suggesting a potential mechanism involving suppression of HPA axis hyperactivity and restoration of nitric oxide (NO) synthesis. This indicates a dual mechanism during stress relief involving both reversal of pathological inhibition and restoration of physiological function. This validates that forest therapy, while improving psychological states, can positively influence bodily functions through specific physiological mechanisms.

Key words: Forest therapy, Psychological stress, College students, FeNO, Stress stratification, Psychophysiological effects, Nonpharmacological intervention