Exploring the effects of short-term forest bathing on anxious medical undergraduates' stressful emotions using near-infrared functional brain imaging and facial expression technology

BACKGROUND: Enrolled medical undergraduates face high exam competition and stress, reducing life quality, well‐being, learning abilities and health; supporting their exam stress management is critical. This study used a 2‐h forest bathing intervention to alleviate their exam‐related stress. METHODS: One week prior to the intervention, 160 students were recruited via university bulletin boards; eligibility screening, defined by a State‐Trait Anxiety Inventory‐State score >40, was administered 1 day before the 2‐h sensory exposure. Ultimately, 60 final‐examination‐preparing medical undergraduates (male:female = 7:53) were randomly assigned to two groups (n = 30 per group). Analyses focused on oxygenated hemoglobin (oxy‐Hb) levels in the prefrontal cortex (PFC), physiological functions, and psychological changes under specific tasks. RESULTS: Forest environments characterized by lower noise levels, and higher negative air ion concentrations‐with a comfort index of 0.971‐1.368 (vs. 2.221‐3.647 in urban areas) and negative oxygen ion concentrations of 1,000‐1,200 ions/cm3 (vs. 400‐500 ions/cm3 in urban areas). For the PFC region, forest group had significantly greater oxy‐Hb reduction during the Trier Social Stress Test (TSST) [t(29) = 3.038, p = 0.005]. At the channel‐specific level, forest group had decreased oxy‐Hb in the left PFC and bilateral Frontopolar Area during the TSST, while the urban group exhibited increased oxy‐Hb in the right PFC during the MT. No between‐group oxy‐Hb differences were observed in the Stroop task or rumination task. Forest group showed lower heart rate [F(1,57) = 4.227, p = 0.044], salivary cortisol [F(1,57) = 4.590, p = 0.036], higher Nature Connection Scale [F(1,57) = 4.822, p = 0.032], Digit Span Backward Test [F(1,57) = 6.164, p = 0.016], Montreal Cognitive Assessment scores [F(1,57) = 12.040, p < 0.001], lower Rumination‐Reflection Questionnaire [F(1,57) = 11.318, p = 0.001]/Perceived Stress Scale scores [F(1,57) = 6.076, p = 0.017], 56.7% positive facial expressions (U = 263.000, n = 60, p = 0.002), and elevated positive affect [Profile of Mood States: F(1,57) = 17.063, p < 0.001]. CONCLUSION: Short‐term forest bathing reduces physiological stress markers, enhances nature connectedness/positive emotions, alleviates stress via modified cerebral blood flow, and improves memory and reduce cognitive fatigue to a certain extent. As a low‐cost, easy‐to‐implement strategy, it is may recommended for enrolled medical undergraduates' mental health curricula to build sustainable stress management.