Original ResearchPsychological effects of forest environments on healthy adults: Shinrin-yoku (forest-air bathing, walking) as a possible method of stress reduction
Introduction
Maintaining mental health is one of the main issues related to disease prevention in developed countries,1, 2 with poor mental health often associated with the occurrence and risk of certain diseases.3, 4, 5, 6, 7 For this purpose, various stress management and relaxation techniques have been proposed.8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 In Japan, shinrin-yoku (staying and/or walking in forests in order to promote physiological and psychological health by breathing in the volatile substances released by trees) was first proposed in the 1980s and has since become a recognized relaxation activity.19, 20 Since forests occupy 64% of the land in Japan,21 participation in shinrin-yoku is easily accessible. According to a public opinion poll conducted in Japan in 2003, 25.6% of respondents had participated in shinrin-yoku in the previous year.22 Furthermore, 56.8% of respondents expressed a desire to spend future holidays in rural and/or mountainous forested areas, and of these, 66.6% expressed an interest in shinrin-yoku for health promotion,22 indicating the popularity of shinrin-yoku in Japan. Moreover, shinrin-yoku is possible in forest environments anywhere in the world.
It is known that natural environments have various beneficial effects on human health. Indeed, most European health resorts catering for rehabilitation and optimization of health conditions are located in natural environments.23 In its guidelines, the Japanese Ministry of Health, Labour and Welfare recommends regular interaction with the natural environment.2 Natural environments are considered to be ‘therapeutic landscapes’24, i.e. places, settings, situations, locales and milieus associated with treatment and healing and the maintenance of health and wellbeing, the concept of which was developed in the 1990s.24, 25, 26 This wide concept includes both physical environments and psychological environments such as humanistic landscapes (e.g. a sense of place).24, 25 Communal gardens for elderly people are one example of a therapeutic landscape related to the green environment.27
However, due to the scarcity of studies on the benefits of green environments28, 29 and shinrin-yoku, the above effects have not yet been clarified and no guidelines exist regarding what effects can be expected and how they can be maximized. Recent studies have revealed the acute psychological and physiological effects of a few hours of shinrin-yoku. For example, natural killer cell activity and immunoglobulin levels were shown to increase,20 while systolic blood pressure and noradrenaline and cortisol levels were shown to decrease.30 Furthermore, negative emotions have been shown to decrease and positive emotions increase after participation in Shinrin-yoku.31 In addition, research aimed at finding a cure for diabetes has shown that walking in a forest is more effective at decreasing blood glucose levels than other activities such as exercise on a cycle ergometer or treadmill, or underwater exercise.19
Most of the above studies were conducted with specific subsets of up to 20 healthy participants, usually students. Since the acute effects of shinrin-yoku in a large healthy population and the factors related to these effects remain unknown, knowledge from existing studies cannot be directly applied to research in the field of public health. Therefore, the aims of the present study were: (1) to examine the acute psychological effects of shinrin-yoku in a large number of participants; and (2) to identify the factors related to these effects.
Section snippets
Study location and participants
The Ethics Committee of Kyoto University approved the study protocol, and written informed consent was obtained from all volunteers. This survey was conducted in Tokyo University Forest, Chiba, Japan.32 Participants were healthy male and female volunteers aged 20 years or over who visited the forest over 4 days in November and December 2004, and who agreed to participate. Participants were required to complete a self-administered questionnaire on two occasions whilst at the forest [once on
Outcome measures
As there are few authorized questionnaires that can be used to measure participants’ momentary emotions, the following were employed: (1) the Multiple Mood Scale-Short Form 33, 34 (MMS-SF); and (2) State-Trait Anxiety Inventory A-State Scale35, 36 (STAI-S; scores range from 20 to 80). The STAI-S is used for measurements of anxiety, while the MMS, which was developed for use in Japan, is used to measure eight momentary emotions, each of which is scored using five four-point items (1=do not feel
Statistical analysis
SPSS 10.0J for Windows was used for all statistical analyses. First, two-way analysis of variance (ANOVA) was conducted using the environment (E; the forest vs. control) and time of completion of each survey (T; the first survey vs. the second survey on each day). Since conditions on the control day (i.e. degree of exercise,45, 46 subjective feelings and objective activities) varied among participants, the effect on participants’ emotions on the control day was considered using stratified
Results
In total, 541 people agreed to participate in the survey. Of these, 498 (244 males, 254 females; mean age±SD: 56.2±10.6 years) people were included in the analyses. The mean duration of stay in the forest was 2 h 20 min±51 min, and the mean distance walked was 5.7±1.7 km. Regarding levels of enjoyment of walking in forests, 475 participants (95.4%) responded that they ‘like’ doing so, 20 (4.0%) chose ‘no preference’, and none of the participants responded that they ‘dislike’ walking in forests.
The
Discussion
This study revealed that acute emotions are improved by participation in shinrin-yoku. Some cohort studies have reported that hostility, depression and anxiety are related to the risk of coronary heart diseases (CHD).37, 38, 39, 40, 41 Moreover, while a positive emotional style has been shown to decrease the risk of common colds,42 an absence of positive wellbeing has been related to mortality.43 In this study, hostility and depression scores decreased significantly as a result of participation
Acknowledgements
The authors thank the staff of Tokyo University Forest, Chiba, the Forest Instructor Association, Chiba, Dr. Takahide Kagawa of the Forestry and Forest Products Research Institute and Mr. Ken Okumura of the University of Tsukuba for their co-operation in collecting data. This study was supported by the Society for the Study of Forest Therapy, Japan.
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