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

## TL;DR

A 2-hour forest bathing session helps reduce stress and improve mental well-being in anxious medical students.

## Contribution

This study demonstrates the effectiveness of short-term forest bathing in reducing stress in medical undergraduates using brain imaging and facial expression analysis.

## Key findings

- Forest bathing significantly reduced physiological stress markers like heart rate and cortisol.
- Participants showed increased positive emotions and improved cognitive performance after the intervention.
- Forest bathing led to decreased oxy-Hb in the prefrontal cortex during stress-inducing tasks.

## Abstract

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.

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.

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].

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.