Trends in research related to "Shinrin-yoku" (taking in the forest atmosphere or forest bathing) in Japan

The effect of cognitive behavior therapy-based "forest therapy" program on blood pressure, salivary cortisol level, and quality of life in elderly hypertensive patients

OBJECTIVE

This article aimed to develop the "forest therapy" program, which is a cognitive behavior therapy (CBT)-based intervention program using forest environment, and investigate its effects on blood pressure (BP), salivary cortisol, and quality of life (QoL) measures in patients with hypertension.

METHODS

A total of 56 men and women were enrolled for this study, being referred from local health centers in Republic of Korea, from April to October 2009. They were conveniently assigned to either "forest" group participating in the forest therapy program or control group doing self-monitoring of BP. Measurements of salivary cortisol level and QoL were done at initial visits and at 8-week final visits.

RESULTS

Both groups did not differ significantly in baseline clinical characteristics. The BP change at week 4 and week 8 did not differ between the two groups. Salivary cortisol level reduction was significantly larger and QoL measures improved significantly more in the forest group at week 8 compared with the control group.

CONCLUSIONS

The forest therapy program did not induce prolonged systolic blood pressure (SBP) reduction. However, considering the significant decrease in cortisol level and improvement in QoL measures, this may be a useful model of community hypertension management program.

[Psychological relaxation effect of forest therapy: results of field experiments in 19 forests in Japan involving 228 participants]

OBJECTIVES

In the present study, we aimed to clarify the psychological effects of shinrin-yoku (taking in the atmosphere of the forest) by conducting field experiments.

METHODS

The experiments were conducted in 19 forested and urban areas in Japan during the 2007-2010 period. Twelve male students participated at each of the 19 areas (a total of 228 persons). Subjective ratings of "comfortable-uncomfortable", "soothing-stimulating", and "natural-artificial" feelings were conducted after each of the participants had viewed the scenery for 15 min in the forested and urban areas. A postviewing questionnaire on "stressed-refreshed" feelings was also administered and the Profile of Mood State (POMS) questionnaire was employed to assess six aspects of mood before and after viewing the sceneries.

RESULTS

The forest environments were perceived as significantly more "comfortable", "soothing", and "natural" than the urban environments after viewing the sceneries. The score for "refreshed feeling" was also significantly higher in the forested areas. The score for the "vigor" subscale of POMS was significantly higher after viewing the scenery in the forested areas, whereas the scores for negative feelings such as "tension-anxiety", "depression-dejection", "anger-hostility", "fatigue", and "confusion" significantly decreased.

CONCLUSION

Collectively, these results suggest that the forest environments have significant beneficial and relaxing effects on human's moods compared with the urban environments.

[Preventive medical effects of nature therapy]

Five million years has passed since a subset of primates recognizably became human. Because we have already spent more than 99.99% of our evolutionary history in natural environments, it is thought that we are essentially adaptive to nature. However, we live in a society 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 Japan. As a result, these subjects sitting in natural surroundings showed decreases in the following physiological indices compared with the 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 shows that stressful states can be relieved by forest therapy. It should also be noted that parasympathetic nerve activity increased by 55.0%, indicating a relaxed state. The results of walking experiments were also similar. Li et al. demonstrated that immune functions are enhanced by forest therapy. Middle-aged employees volunteered to participate in these experiments. NK (natural killer cells) activity, as an indicator of immune function, increased by 56% on the second day and returned to normal levels. A significant increase of 23% was maintained for 1 month even after these subjects returned to urban life, clearly illustrating the preventive medical effects of nature therapy. We expect nature therapy to play an increasingly important role in preventive medicine in the future.

[Effect of forest therapy on the human psycho-neuro-endocrino-immune network]

Traditional thinking considered the nervous system, endocrine system and immune system to be independent of each other. However, it is now widely accepted that these systems interact through the psycho-neuro-endocrino-immune network. The nervous system affects the endocrine and immune systems by releasing neurotransmitters through the hypothalamus in the hypothalamic-pituitary portal circulation. The endocrine system affects the nervous and immune systems by secreting hormones and the immune system feeds back to the nervous and endocrine systems via cytokines. Forest therapy reduces sympathetic nervous activity, increases parasympathetic nervous activity, and regulates the balance of autonomic nerves. As a result, forest therapy decreases blood pressure and heart rate and has a relaxing effect. Forest therapy affects psychological responses via the brain and nervous system thereby decreasing the scores for anxiety, depression, anger, fatigue, and confusion, and increasing the score for vigor in the POMS test. Forest therapy acts on the endocrine system to reduce stress hormone levels such as urinary adrenaline, urinary noradrenaline, salivary cortisol, and blood cortisol levels and shows a relaxing effect. Forest therapy also acts directly and indirectly on the immune system to promote NK activity by increasing the number of NK cells and intracellular levels of anticancer proteins such as perforin, granulysin and granzymes. Taken together, forest therapy brings various effects on human health via the psycho-neuro-endocrino-immune network.

[Subjective relaxing effect of a hospital's rooftop forest on elderly patients requiring care]

OBJECTIVES

To clarify the relaxing effects of a 5-min stay in a hospital's rooftop forest on elderly patients requiring care.

METHODS

This was a within-subject, cross-sectional study. The participants were 30 elderly female patients requiring help in walking, aged 81.2±6.4 (mean±SD). A simplified emotional 7-point rating scale from -3 to 3 for 5 pairs of emotions, which was derived from the two-question Whooley Depression Screen, was used as a subjective indicator. The experimental areas were the rooftop forest that covered an area of 122 m(2) on the rooftop of a four-story health service facility and an outdoor car park area (as the control area). The participants were instructed to sit still in a wheelchair and view the scenery for 5 min in each experimental area and were then assessed. Data from the participants during exposure to the rooftop forest were compared with those during exposure to the control area. First, 15 participants moved to the rooftop forest from the preroom, and the other 15 moved to the outdoor car park area, and then they moved to the other site to eliminate any order effect.

RESULTS

In the rooftop forest, the mean scores of the simplified emotional rating were 1.70 (1.17 for control) for "hopeful", 1.70 (1.17) for "interest in doing things", 1.53 (1.10) for "enjoyment", 1.67 (1.17) for "calm", and 2.03 (1.30) for "secure". The scores were all significantly higher than those in the control (p<0.01).

CONCLUSION

It was demonstrated that a visit to the rooftop forest induced a significant subjective relaxing effect in elderly female patients requiring care.

Effect of forest bathing on physiological and psychological responses in young Japanese male subjects

OBJECTIVE

To provide scientific evidence supporting the efficacy of forest bathing as a natural therapy by investigating its physiological benefits using biological indicators in outdoor settings.

STUDY DESIGN

Within-group comparisons were used to examine psychological and physiological responses to exposure to real forest and urban environments.

METHODS

Young Japanese male adults participated in a 3-day, 2-night field experiment. Physiological responses as well as self-reported psychological responses to forest and urban environmental stimuli were measured in real settings. The results of each indicator were compared against each environmental stimulus.

RESULTS

Heart rate variability analysis indicated that the forest environment significantly increased parasympathetic nervous activity and significantly suppressed sympathetic activity of participants compared with the urban environment. Salivary cortisol level and pulse rate decreased markedly in the forest setting compared with the urban setting. In psychological tests, forest bathing significantly increased scores of positive feelings and significantly decreased scores of negative feelings after stimuli compared with the urban stimuli.

CONCLUSION

Physiological data from this field experiment provide important scientific evidence on the health benefits of forest bathing. The results support the concept that forest bathing has positive effects on physical and mental health, indicating that it can be effective for health promotion. Despite the small sample size in this study, a very clear tendency towards positive physiological and psychological outcomes in forests was observed.