Prescribing Green Dose for College Students' Mental Health: Identifying Thresholds for Green Space Exposure Duration, Frequency, and Cumulative Dose via Smartwatch
College students face increasing mental health challenges, including elevated stress and poor sleep quality. Exposure to natural environments has been associated with psychological and physiological benefits, yet the multidimensional relationships be...
Key Findings
College students face increasing mental health challenges, including elevated stress and poor sleep quality. Exposure to natural environments has been associated with psychological and physiological benefits, yet the multidimensional relationships between green space exposure (GSE) and mental health remain insufficiently understood, particularly regarding exposure duration, frequency, and cumulative weekly exposure. This study examined associations between campus green space exposure and mental health outcomes among college students during a six-week wearable-based observational study using Apple Watch data. 43 healthy students from Shanghai Jiao Tong University participated in repeated assessments across baseline and intervention periods. Distinct exposure dimensions were associated with different mental health outcomes. Single-session exposure durations of approximately 17-35 minutes were associated with sleep-related outcomes. Weekly exposure frequency of approximately 3 sessions per week showed the strongest associations with daytime functioning, while cumulative weekly exposure of approximately 70-120 minutes was associated with emotional outcomes and differences in HRV amplitude patterns. These findings suggest that multidimensional green space exposure may relate differently to specific psychological and physiological outcomes among university students. This study demonstrates the feasibility of using wearable devices to support fine-grained ecological exposure assessment and may help inform future research on green space exposure and mental health in university settings.