Purpose   The purpose of this study was to determine the relaxing effects of a hospital rooftop forest on healthcare workers and to assess the influence of trait anxiety. Methods   Sixteen male workers (aged 37.1±10.6years, mean±SD) and 56 female workers (aged 43.5±11.2years) participated in this study. Females were divided into 32low-to medium-anxiety and high-anxiety groups according to their trait anxiety as per the State Trait Anxiety Inventory-Form JYZ (STAI-Form JYZ). The experimental site was a rooftop forest, which covered an area of 122 m2, on the fourth storey of a health service facility. An outdoor car park area of 170m2, near the same facility, was used as a control. All participants were assessed individually at 3 sites: pre-room, rooftop forest, and outdoor car park area. Participants sat still in a wheelchair and viewed the scenery for 5minutes in each experimental area. The subjective effect was analyzed using the state anxiety as per the STAI-Form JYZ and the Profile of Mood States (POMS). The data between the rooftop forest and the control was compared within each participant. The participants were also divided into sex- and age-matched groups: A and B. Group A moved to the rooftop forest from the pre-room and group B first moved to the control area to eliminate the order effect. Results and Discussion   After viewing the rooftop forest, the mean values of state anxiety as per the STAY-Form JYZ showed a significant (p<0.01) decrease to 34.6±8.1 (43.4±8.4for control) in males and to 36.3±10.2 (45.8±8.8) in females. In low- to medium-anxiety females, state anxiety significantly (p<0.01) decreased to a“very low”anxiety state (“low” for control), and in high-anxiety females, it significantly (p<0.01) decreased to a “low” anxiety state (“intermediate” for control). As per the T-score of POMS, in males, “Fatigue” significantly (p<0.01) decreased to 39.0±7.5 (41.1±7.0) and “Vigor” significantly (p<0.01) increased to 43.3±10.4 (37.9±8.1). In females, “Tension-Anxiety” significantly (p<0.01) decreased to 39.7±7.7 (43.7±8.8), “Depression-Dejection” significantly (p<0.01) decreased to 43.5±6.3 (45.4±7.6), “Fatigue” significantly (p<0.01) decreased to 40.7±7.3 (43.6±8.5), and “Vigor” significantly (p<0.01) increased to 46.2±10.8 (38.9±8.0). After viewing the rooftop forest, the “iceberg profile” observed in the visual pattern of low- to medium-anxiety females indicated positive feelings. The “negative wing” indicating negative feelings observed in high-anxiety females in the pre-room disappeared after viewing the rooftop forest. Conclusion   We demonstrated that a short exposure to a rooftop forest environment induces a significant subjective relaxation effect in healthcare workers and that this effect is influenced by individual trait anxiety.

  The human species have existed for 6-7 million years. Because over 99.99% of our evolutionary history has been spent in natural environments, it is considered that we are adaptive to nature1). However, we now live in a society that is characterized by urbanization and artificiality, despite our physiological functions still being adapted to nature.   We conducted experiments involving 420 subjects at 35 different forests throughout Japan2). Participants in natural surroundings showed the following physiological decreases compared with those in an urban control group: 12.4% decrease in cortisol level, 7.0% decrease in sympathetic nervous activity, 1.4% decrease in systolic blood pressure, and 5.8% decrease in heart rate. This suggests that stressful states can be relieved by forest therapy. In addition, parasympathetic nervous activity was enhanced by 55.0%, indicating a relaxed state. The results of similar experiments that involved walking in forests were equivalent. Li et al. demonstrated that immune function was enhanced by forest therapy in middle-aged employees who volunteered to participate in these experiments. Natural killer cell activity, an indicator of immune function, was enhanced by 56% on the second day and returned to normal levels. A significant increase of 23% was maintained for 1 month even after returning to urban life, clearly illustrating the preventive benefits of forest therapy3).   In conclusion, forest therapy had preventive benefits and facilitated physiological relaxation and immune recovery4) (Figure 1).