Many stressors of urban life are increasingly driving humans to seek some form of stress relief [1
]. In modern urbanized societies, acute and chronic stress and insufficient recovery from stress are well known as increasing problems and causes for long-term effects on health [2
]. Stress is an important public health interest that is related to mental health problems, such as burnout syndrome, as well as cardiovascular, gastroenterological, immunological and neurological diseases [4
]. This suggests that stress control is a vital issue in maintaining good health and preventing stress-related diseases in urbanized societies. Natural environments, including urban parks and natural, secondary, artificial man-made forests are generally associated with stronger positive health effects as compared to urban environments [5
]. For instance, natural scenes bring higher tranquility and a reduced feeling of danger compared to urban scenes [6
], while outdoor recreation in a “green” environment has been shown to relieve stress among urban inhabitants [7
]; hence, evidence to date seems to indicate the positive health effect of a natural setting.
Several studies conducted in different countries have also reported that natural environments provide better emotional, physiological, restorative effects [9
] and work performance [13
] than urban environments. These positive effects are shown, for example, in lowered blood pressure, muscle tension and skin conductance and increased brain activity in the alpha frequency band: a change to positively-toned self-reported emotions and a recovery of attention-demanding cognitive performances after stress situations [14
]. Furthermore, being outdoors seems to have revitalizing (positively-toned, energized state) effects [18
]. Ulrich [19
] reported that surgical patients assigned to rooms with windows overlooking natural scenery with trees had shorter postoperative hospital stays, received fewer negative comments in nurses’ notes and took fewer potent analgesics than those in similar rooms with windows facing a brick wall. Mitchell and Popham [20
] reported a link between the amount of green space in residential areas and mortality in a population study conducted in the U.K. They found that a health gap derived from economic disparity was smaller for those living near green places. Based on the analysis of distance between residences and green space and the amount of green space, Maas et al.
] reported that more green space brought better perceived general health. Conversely, from a preventive perspective, Roe and Aspinall [22
] mentioned that rural walks benefited affective and cognitive restoration, especially in the poor mental health group, and highlighted the potential for green space as a method of preventing mental disorders.
The project on the therapeutic effects of forests was launched in 2004 as part of scientific and practical investigations into the health effects of forests in Japan [23
]. In Japan, forests cover 68.2% of the total land area [24
]. Walking in forests is a common recreational activity in Japan and is believed to promote both physical and mental health by breathing in fresh air and substances released from trees, as well as exercise and/or other healing factors associated with the forest environment [25
]. Recent Japanese studies reported lower concentrations of cortisol, blood pressure and pulse rates, decreased sympathetic nerve activity (as measured by the low frequency/high frequency (LF/HF) component of heart-rate variability (HRV), enhanced parasympathetic nerve activity (as measured by the HF component of HRV) and higher levels of natural killer (NK) cell activity (a typical index of human immune function) in the human body when subjects walked or sat in a forest environment, as opposed to when they walked or sat in an urban environment [8
With regard to the psychological responses in Japanese forest environments, the Multiple Mood Scale-Short Form (MSS) [29
] showed higher scores for friendliness and well-being, and the MMS score of depression and State-Trait Anxiety Inventory (STAI) State Scale [31
] scores were lower on days spent walking in the forest compared with the control day, especially among individuals who felt chronic mental stress [12
]. Here, the reason why forests give us a health benefit can explain Miyazaki’s Nature Therapy Theory that human psychological and physiological functions have evolved to adapt to the forest environment. Therefore, forest stimulation easily facilitates psychological and physiological relaxation [32
In a continuation of the Therapeutic Effects of Forests project, the present study was intended to investigate the well-being effects of short-term forest walking and viewing (“forest bathing”). Thus, the present study contributes to the issue by using walking and viewing in a reversed order compared to many previous studies [23
]. One earlier study using walking and viewing, in that order, reported only physiological results, showing that, e.g., pulse rate and diastolic blood pressure were lower in the forest area than in the city area [28
]. The hypothesis in our study is that both environment (forest vs.
urban) and activity (walking and viewing) would influence psychological outcomes.
An additional aim was to enhance basic research using several psychological methods. Emotional responses were previously measured by the Profile of Mood States (POMS) (e.g., [23
]), MMS (e.g., [29
]), STAI (e.g., [12
]) and Zuckerman Inventory of Personal Reactions (ZIPERS) (e.g., [36
]). However, other emotional measures have been seldom used. To date, restorative outcome scales have been used mainly in studies of favorite places [37
]. Moreover, vitality is a new concept, which is related to restoration, but believed to be a distinct concept [18
]; for which further studies comparing urban and natural settings are required. Moreover, the combination of the psychological measures in our study is novel in that an earlier study using Restorative Outcome Scale (ROS) and Subjective Vitality Scale (SVS) had the Positive and Negative Affect Schedule (PANAS), but not POMS, as an emotional measure (and used viewing before walking) [34
]. A recent study with only viewing used POMS, but not other psychological measures [38
]. We believe that many-sided descriptions of emotional and restorative responses might help environmental planning and management professionals develop and measure the qualities of a comfortable forest environment appropriate for forest bathing in the future.
In this study, we investigated the emotional, restorative and revitalizing effects of short-term walking and viewing in forest and downtown areas.
Initially, the hypothesis in our study that both environment and activity would influence psychological effects could be supported, because significant interaction terms between the environment and activity were confirmed regarding the POMS indexes, ROS and SVS.
Although the subjects were once introduced to the walking course before the experiment, no statistical differences between the two experimental groups in any of the ten scales were found before the experiment. However, feelings of vigor and positive effects, as well as feelings of subjective recovery and vitality were stronger in the forest environment (after the combined effect of walking and viewing) than in the urban environment (the same timing as forest environments).
The limitations of the present study include the fact that it was focused on the psychological effects just after the experiment, excluding potential long-term effects. This remains a topic for future studies. The experiments were carried out in flat, bright and well-managed forest areas. However, the psychological effects of forest settings may depend on the state of vegetation in the forest, as well as forest management and care. Comparisons between different kinds of forests are thus warranted in future studies. Furthermore, studies comparing different kinds of urban areas are also warranted. Methodologically, the scales of restorative outcomes and subjective vitality seemed to record somewhat similar phenomena. This applied even more so after the respondents had been exposed to the experimental manipulation (a forest or urban setting; the correlations were lower before the experiment). We need further studies to confirm whether this is due to the respondents’ positive attitude toward the experiment, to some true experimental effects or to convergence between the concepts of restoration and vitality.
In summary, compared to the urban control, this study clarified the following psychological recovery effects derived from a short stay in the forest environment:
Forest bathing improved mood;
Forest bathing heightened positive affect;
Forest bathing induced a feeling of subjective restoration;
Forest bathing induced a feeling of subjective vitality.