Mood and physiological effects of visual stimulation with images of the natural environment in individuals with depressive and anxiety disorders.

BACKGROUND: Nature therapies are gaining attention as non-pharmacological treatments for depressive and anxiety disorders, but research on their effectiveness in patients is limited. This study investigates the mood-improving effects of visual stimulation with natural environmental images in patients with depressive and anxiety disorders. METHODS: We conducted a randomized crossover comparison trial involving 60 right-handed adult participants with depressive or anxiety disorders and receiving outpatient treatment. Visual stimuli of natural environments consisted of green-themed nature images, while the control stimuli featured urban scenes dominated by buildings. The stimulation lasted for 3 min, during which orbital prefrontal brain activity was measured using a 2-channel Near-infrared Spectroscopy (NIRS) system, and heart rate variability was assessed using fingertip accelerated plethysmography. RESULTS: Mood enhancement effects were observed in both the depressive and anxiety disorder groups following visual stimulation with nature images. In the depression group, orbital prefrontal oxygenated hemoglobin concentration significantly increased after visual stimulation with nature images, while there were no significant changes in the anxiety group. However, in the anxiety group, a correlation was found between reduced orbital prefrontal oxygenated hemoglobin in response to nature images and increased mood-enhancement. Furthermore, the severity of depressive symptoms did not significantly affect the intervention effects, whereas heightened anxiety symptoms was associated with a smaller mood enhancement effect. DISCUSSION: Our study demonstrates the benefits of nature image stimulation for patients with depressive and anxiety disorders. Differential orbital prefrontal brain activity impacts notwithstanding, both conditions exhibited mood enhancement, affirming the value of nature image stimulation.

Physiological Effects of Visual Stimulation by a Japanese Low Wooden Table: A Crossover Field Experiment.

The purpose of this study was to evaluate the physiological effects of visual stimulation by a unique Japanese low wooden table on the prefrontal cortex and autonomic nervous activities. A within-participants experiment with 26 male university students was conducted in a Japanese-style room. The visual stimuli were a low wooden table (WT) made of Japanese cypress and a low cloth-covered table (control) for an exposure time of 90 s. Near-infrared spectroscopy was used to measure the prefrontal cortex activity in the left and right prefrontal cortices as an indicator of oxyhemoglobin (oxy-Hb) concentration. Autonomic nervous activity was measured as an indicator of sympathetic (low-frequency/high-frequency component ratio, LF/HF), and parasympathetic (high-frequency components, HF) nervous activities were assessed by heart rate variability. Furthermore, the modified semantic differential method and the Profile of Mood States 2nd edition were used to measure psychological responses. Physiologically, the oxy-Hb concentration in the left prefrontal cortex and ln (LF/HF) were significantly lower during visual exposure to the WT than to the control. Psychologically, more comfortable, relaxed, and natural impressions, as well as improved mood states, were reported during visual stimulation to the WT than to the control. This study demonstrated that viewing a WT led to physiological relaxation and had a positive psychological effect on the participants.

Physiological adjustment effect of visual stimulation by fresh rose flowers on sympathetic nervous activity.

Introduction: As modern societies are often stressful due to urbanization and artificialization, the physiological relaxing effects of natural environments or nature-derived stimuli on humans have attracted attention and scientific data are being accumulated. It is known that there is inter-individual variation in these effects. The study aim was to apply the law of initial values to investigate the physiological adjustment effect of viewing fresh roses on sympathetic nervous activity. Methods: In this crossover study, a total of 214 high school students, office workers, healthcare workers, and elderly people were analyzed. The participants viewed fresh roses in a vase for 4 min. In the control condition, participants did not view any fresh roses during the period. To offset any order effect, participants received visual stimuli in the order of fresh roses then the control (no fresh roses) or the control and then fresh roses. ln (LF/HF) of heart rate variability (HRV) obtained from a-a interval measurements using an acceleration plethysmograph and used as an index of sympathetic nervous activity. The initial value was ln (LF/HF) of HRV during the control viewing (no fresh roses), and the change value was ln(LF/HF) of HRV during visual stimulation by fresh roses minus the control viewing. Results and Discussion: The correlation between the two was assessed by determining Pearson's correlation coefficient r, which was significantly negative. A physiological adjustment effect was observed such that participants with high initial sympathetic nervous activity showed a decrease in activity after visual stimulation with fresh roses, whereas participants with low initial activity showed an increase.

Relaxation Effect of Nature Sound Exposure on Gambling Disorder Patients: A Crossover Study.

Objective: Gambling disorder (GD) has been associated with economic, social, mental, and physical problems. Alternative leisure activities or stress-relieving activities have been adopted as part of GD treatment. Moreover, it has been proven that activities utilizing the natural environment, such as shinrin-yoku, have a relaxing effect on healthy people. In this study, we examined the physiological and psychological responses of patients with GD to determine whether nature therapy could reduce their stress responses. Design: This study included 22 Japanese male participants who were found to be pathological gamblers, with a South Oaks Gambling Screen score of ≤5. We exposed the participants to the digital nature sounds of insects and city sounds of a scramble intersection. The nature and city sounds were presented in a counterbalanced order. Outcome measures: A two-channel near-infrared spectroscopy system was used to measure the changes in oxyhemoglobin (oxy-Hb) concentrations in the bilateral prefrontal cortex. The heart rate variability was measured to evaluate the autonomic nervous activity. Subjective evaluation was performed using the modified version of the semantic differential method and the Profiles of Mood States, Second Edition (POMS2). Results: The oxy-Hb level in the bilateral prefrontal cortex significantly decreased. No significant difference in the high-frequency (HF) and low-frequency/HF ratio was observed. The subjective evaluation indicated that the participants experienced increased comfort and relaxation and had more natural feelings. Nature sounds significantly decreased the POMS2 negative emotion subscale and total mood disturbance scores and increased the positive emotion subscale scores. Nature-based stimulus exposure induces physiological relaxation and other positive effects among individuals even with GD. Conclusion: Exposure to nature-based sounds induces physiological relaxation and other positive responses among individuals with GD. In patients with GD, nature sounds produce the same relaxation response as in healthy individuals. (Umin.ac.jp under registration number: UMIN000042368).

Seasonal Differences in Physiological Responses to Walking in Urban Parks.

The aim of the current study was to assess seasonal differences in physiological responses to walking in urban parks. In total, 51 Japanese male university students participated in this research. During each season, the participants walked for 15 min in an urban park and a city area, which was used as the control site. Heart-rate variability and heart rate were used as physiological indicators. The mean values of each indicator in a comparison between walking in an urban park and a city area were compared according to each season. In addition, to show the physiological effect of walking in an urban park, differences (between walking in an urban park and walking in a city area) were calculated. Then, differences according to each season were compared. The results showed that the participants had increased parasympathetic nervous system activity in all seasons except summer. Moreover, they had decreased sympathetic nervous system activity in spring and fall and decreased heart rate in all seasons. Compared with walking in urban parks in summer, walking in urban parks in spring, fall, and winter had a greater relaxation effect on parasympathetic and sympathetic nervous system activities; hence, the physiological effects of walking in urban parks vary based on season.

Physiological and Psychological Responses of Viewing a Waterfall Image: A Crossover Study.

Growing interest in the relaxation effect of nature has elicited demands for scientific verification of the various natural elements. This study investigated the physiological and psychological responses of 27 females in their 20 s to viewing a waterfall and urban images (control) presented via a large, high-resolution display for 90 s. High-frequency [HF] for parasympathetic nervous activity and the ratio of low-frequency (LF)/[LF + HF] for sympathetic nervous activity by heart rate variability and heart rate were recorded. Simultaneous changes in oxyhemoglobin concentration in the prefrontal cortex were recorded by near-infrared time-resolved spectroscopy. The modified semantic differential method and Profile of Mood States Second Edition were used to assess the psychological effects on the participants after viewing each image. The results showed that viewing the waterfall image, compared with viewing the urban image, (1) increased sympathetic nervous activity; (2) provided comfortable, relaxed, and natural impressions; (3) improved mood states. In conclusion, visual contact with a waterfall image physiologically activated sympathetic nervous activity and psychologically evoked positive moods and feelings.

The Mood-Improving Effect of Viewing Images of Nature and Its Neural Substrate.

It has been recently suggested that contact with nature improves mood via reducing the activity of the prefrontal cortex. However, the specific regions within the prefrontal cortex that underlie this effect remain unclear. In this study, we aimed to identify the specific regions involved in the mood-improving effect of viewing images of nature using a 52-channel functional near-infrared spectroscopy (fNIRS). Specifically, we focused on the orbitofrontal cortex (OFC) and dorsolateral prefrontal cortex (dlPFC), two regions associated with affective processing and control. In a randomized controlled crossover experiment, we assigned thirty young adults to view images of nature and built environments for three minutes each in a counterbalanced order. During image viewing, participants wore a fNIRS probe cap and had their oxyhemoglobin (oxy-Hb) measured. Immediately following each image viewing, participants indicated their mood in terms of comfortableness, relaxation, and vigor. Results showed that viewing images of nature significantly increased comfortableness and relaxation but not vigor compared to viewing images of built environments, with a large effect size. Meanwhile, the concentration of oxy-Hb in only the right OFC and none of the other regions significantly decreased while viewing the images of nature compared to built environments, with a medium effect size. We speculate that viewing images of nature improves mood by reducing the activity of or calming the OFC. Since the OFC is hyperactive in patients with depression and anxiety at rest, contact with nature might have therapeutic effects for them.

Association between the Psychological Effects of Viewing Forest Landscapes and Trait Anxiety Level.

The aim of this study was to validate the psychological advantages of viewing forest landscapes. Moreover, the associations between trait anxiety levels and psychological responses were evaluated. A total of 650 university male students (age, 21.7 ± 1.6 years) viewed a scenery in a forested area and an urban area for 15 min. Furthermore, the Profile of Mood States questionnaire and State-Trait Anxiety Inventory were employed for the assessment of the psychological responses and the level of trait anxiety, respectively, of the participants. Results showed that compared with viewing a city area, viewing forest areas increased positive mood state, such as vigor, and decreased negative mood states. Furthermore, trait anxiety level and changes in the psychological responses such as depression-dejection, fatigue, and confusion after viewing forest landscapes were significantly correlated. The participants with high anxiety levels had greater reduction in negative mood state, including confusion, than those with low anxiety levels. In conclusion, viewing forest landscapes induced psychological relaxation, which was more evident in individuals with high anxiety levels.

Correction: Song, C.; Ikei, H.; Park, B.J.; Lee, J.; Kagawa, T.; Miyazaki, Y. Psychological Benefits of Walking through Forest Areas. Int. J. Environ. Res. Public Health 2018, 15, 2804.

The authors wish to add the following corrections to their paper published in the International Journal of Environmental Research and Public Health [1] [...].

Correction: Lee, J. et al. Acute Effects of Exposure to a Traditional Rural Environment on Urban Dwellers: A Crossover Field Study in Terraced Farmland. Int. J. Environ. Res. Public Health 2015, 12, 1874-1893.

The authors wish to add the following corrections to their paper published in the International Journal of Environmental Research and Public Health [...].

Physiological Benefits of Viewing Nature: A Systematic Review of Indoor Experiments.

Contact with nature has been proposed as a solution to achieve physiological relaxation and stress recovery, and a number of scientific verification outcomes have been shown. Compared with studies of the other senses, studies investigating the visual effects of nature have been at the forefront of this research field. A variety of physiological indicators adopted for use in indoor experiments have shown the benefits of viewing nature. In this systematic review, we examined current peer-reviewed articles regarding the physiological effects of visual stimulation from elements or representations of nature in an indoor setting. The articles were analyzed for their stimulation method, physiological measures applied, groups of participants, and outcomes. Thirty-seven articles presenting evidence of the physiological effects of viewing nature were selected. The majority of the studies that used display stimuli, such as photos, 3D images, virtual reality, and videos of natural landscapes, confirmed that viewing natural scenery led to more relaxed body responses than viewing the control. Studies that used real nature stimuli reported that visual contact with flowers, green plants, and wooden materials had positive effects on cerebral and autonomic nervous activities compared with the control. Accumulation of scientific evidence of the physiological relaxation associated with viewing elements of nature would be useful for preventive medicine, specifically nature therapy.

Physiological and Psychological Effects of Forest and Urban Sounds Using High-Resolution Sound Sources.

Exposure to natural sounds is known to induce feelings of relaxation; however, only few studies have provided scientific evidence on its physiological effects. This study examined prefrontal cortex and autonomic nervous activities in response to forest sound. A total of 29 female university students (mean age 22.3 ± 2.1 years) were exposed to high-resolution sounds of a forest or city for 60 s, using headphones. Oxyhemoglobin (oxy-Hb) concentrations in the prefrontal cortex were determined by near-infrared spectroscopy. Heart rate, the high-frequency component of heart rate variability (which reflects parasympathetic nervous activity), and the ratio of low-frequency to high-frequency (LF/HF) components (which reflects sympathetic nervous activity) were measured. Subjective evaluation was performed using the modified semantic differential method and profiles of mood states. Exposure to the forest sound resulted in the following significant differences compared with exposure to city sound: decreased oxy-Hb concentrations in the right prefrontal cortex; decreased ln(LF/HF); decreased heart rate; improved feelings described as "comfortable,'' "relaxed," and "natural"; and improved mood states. The findings of this study demonstrated that forest-derived auditory stimulation induced physiological and psychological relaxation effects.

Effects of Walking in a Forest on Young Women.

The effects of forest activities on health promotion have received increasing attention. The aim of this study was to evaluate the physiological and psychological effects of brief walks in forests on young women. The experiments were conducted in 6 forests (test) and 6 city areas (control). Overall, 12 participants in each area (60 participants in total, mean age: 21.0 ± 1.3 years) were instructed to walk in a forest and a city area for approximately 15 min; simultaneously, their heart rate variability, heart rate, blood pressure, and pulse rate were measured to quantify their physiological responses to walking. The modified semantic differential method, Profile of Mood States (POMS), and the State⁻Trait Anxiety Inventory (STAI) were used to determine their psychological responses. Walking in a forest was associated with significantly higher parasympathetic nervous activity and lower sympathetic nervous activity and heart rate. In addition, scores for the comfortable, relaxed, and natural parameters and vigor subscale of POMS were significantly higher, whereas scores for negative feelings, such as tension⁻anxiety, depression⁻dejection, anger⁻hostility, fatigue, and confusion, were significantly lower, as were the total mood disturbance of POMS and the anxiety dimension of the STAI. The subjective evaluations were generally in accordance with the physiological responses. A brief walk in a forest resulted in physiological and psychological relaxation effects in young women.

Combined Effect of Walking and Forest Environment on Salivary Cortisol Concentration.

We investigated the effects of walking in a forest environment on salivary cortisol concentrations. Seventy-four young male participants walked for 15 min in forested and urban environments, and saliva was collected before and after walking. Our previous study reported salivary cortisol concentrations after walking only. This study was aimed at clarifying the combined effects of walking and environment by comparing post-walking data with pre-walking data. Walking in a forest environment decreased mean cortisol concentration from 9.70 to 8.37 nmol/L, whereas walking in an urban environment barely changed mean cortisol concentration, from 10.28 to 10.01 nmol/L. Two-way repeated analysis of variance revealed a significant interaction effect between the environment and walking (p < 0.001) in addition to the main effects of each (p < 0.001 and p = 0.001, for walking and environment, respectively). For further analysis, the proportion of participants who exhibited decreased cortisol after forest-walking was compared with the previously reported proportion of participants who exhibited decreased cortisol after viewing forest landscapes. Although the proportion of positive responders was slightly higher after walking (69%) than it was after viewing (60%), this difference was not statistically significant (p = 0.093). The present study revealed a significant combined effect of walking and the environment on cortisol concentrations.

Psychological Benefits of Walking through Forest Areas.

This study aimed to clarify the psychological benefits of brief walks through forest areas. In addition, we aimed to examine the associations between psychological responses and trait anxiety levels. Five-hundred-and-eighty-five participants (mean age, 21.7 ± 1.6 years) were instructed to walk predetermined courses through forest (test) and city (control) areas for 15 min. The Profile of Mood State (POMS) questionnaire and State-Trait Anxiety Inventory were used to assess participants' psychological responses and trait anxiety levels, respectively. The results revealed that walking through forest areas decreased the negative moods of "depression-dejection", "tension-anxiety", "anger-hostility", "fatigue", and "confusion" and improved the participants' positive mood of "vigor" compared with walking through city areas. Furthermore, a significant correlation was found between participants' trait anxiety levels and their changes in the subscale of "depression-dejection" of POMS after walking through forest areas. A more effective reduction in the feeling of "depression-dejection" after walking through forest areas was observed for participants with high trait anxiety levels than for those with normal and low trait anxiety levels. This study showed the psychological benefits of walking through forest areas and identified a significant correlation between psychological responses to walking through forests and trait anxiety levels.

Physiological Effects of Viewing Bonsai in Elderly Patients Undergoing Rehabilitation.

The benefits of various nature-derived stimuli that can be used for stress relief and relaxation has recently gained immense attention; however, there are very few studies about their influence on elderly patients. The present study aims to present the effects of viewing bonsai on autonomic nervous activity, prefrontal cortex activity, and subjective assessment findings of psychological relaxation in elderly patients undergoing rehabilitation. Fourteen participants aged 64⁻91 years (mean age ± standard deviation, 78.6 ± 9.6 years) participated in this study. Miniature potted 10-year-old Japanese cypress bonsai trees were used as visual stimuli. Participants viewed the bonsai for 1 min, and the control comprised of no experimental stimulus. Physiological effects on autonomic nervous activity were assessed by measuring the heart rate variability (HRV) and pulse rate. The effects on prefrontal cortex activity were determined using near-infrared spectroscopy, which involved assessment of oxyhemoglobin concentrations in the left and right prefrontal cortices. Subjective evaluations were achieved by the modified semantic differential method. Viewing bonsai resulted in a significant increase in parasympathetic nervous activity, a significant decrease in sympathetic nervous activity, and a significant increase in the perceptions of feeling "comfortable" and "relaxed." In conclusion, our findings indicated that viewing bonsai induces physiological and psychological relaxation.

Forest Walking Affects Autonomic Nervous Activity: A Population-Based Study.

The present study aimed to evaluate the effect of walking in forest environments on autonomic nervous activity with special reference to its distribution characteristics. Heart rate variability (HRV) of 485 male participants while walking for ~15 min in a forest and an urban area was analyzed. The experimental sites were 57 forests and 57 urban areas across Japan. Parasympathetic and sympathetic indicators [lnHF and ln(LF/HF), respectively] of HRV were calculated based on ~15-min heart rate recordings. Skewness and kurtosis of the distributions of lnHF and ln(LF/HF) were almost the same between the two environments, although the means and medians of the indicators differed significantly. Percentages of positive responders [presenting an increase in lnHF or a decrease in ln(LF/HF) in forest environments] were 65.2 and 67.0%, respectively. The percentage of lnHF was significantly smaller than our previous results on HRV during the viewing of urban or forest landscapes, whereas the percentage of ln(LF/HF) was not significantly different. The results suggest that walking in a forest environment has a different effect on autonomic nervous activity than viewing a forest landscape.

Physiological Effects of Touching the Wood of Hinoki Cypress (Chamaecyparis obtusa) with the Soles of the Feet.

We clarified the physiological effects of tactile stimulation of the soles of the feet with the wood of the Hinoki cypress (Chamaecyparis obtusa) based on measurements of prefrontal cortex and autonomic nervous activities. Nineteen female university-attending students (age: 21.2 ± 0.3 years) were included. Oxy-hemoglobin (oxy-Hb) concentrations in the prefrontal cortex were determined by using near-infrared time-resolved spectroscopy. The high frequency (HF) indicating parasympathetic nervous activity and the ratio of low frequency (LF)/HF indicating sympathetic nervous activity were measured using heart rate variability. To evaluate the psychological effects caused by contact with the materials, the modified semantic differential method was used. The soles of the participants' feet were touched to a 600 × 600-mm plate made of Hinoki, which was finished in non-coating and brushing for 90 s. A marble plate served as the control. Next, subjective evaluation tests were administered to the participants. Compared with touching marble, touching Hinoki significantly (1) decreased the oxy-Hb concentrations in the left and right prefrontal cortices, which indicates decreased prefrontal cortex activity, (2) increased ln(HF), which indicates increased parasympathetic nervous activity, (3) decreased ln(LF/HF) ratio, which indicates decreased sympathetic nervous activity. Additionally, (4) according to subjective evaluations, the participants perceived themselves as being more "comfortable," "relaxed," "natural," "warm," "uneven," "dry," and "soft" after touching Hinoki. Thus, our cumulative findings indicate that touching Hinoki with the soles of the feet induces physiological relaxation.

Physiological Effects of Visual Stimulation with Forest Imagery.

This study was aimed to clarify the physiological effects of visual stimulation using forest imagery on activity of the brain and autonomic nervous system. Seventeen female university students (mean age, 21.1 ± 1.0 years) participated in the study. As an indicator of brain activity, oxyhemoglobin (oxy-Hb) concentrations were measured in the left and right prefrontal cortex using near-infrared time-resolved spectroscopy. Heart rate variability (HRV) was used as an indicator of autonomic nervous activity. The high-frequency (HF) component of HRV, which reflected parasympathetic nervous activity, and the ratio of low-frequency (LF) and high-frequency components (LF/HF), which reflected sympathetic nervous activity, were measured. Forest and city (control) images were used as visual stimuli using a large plasma display window. After sitting at rest viewing a gray background for 60 s, participants viewed two images for 90 s. During rest and visual stimulation, HRV and oxy-Hb concentration in the prefrontal cortex were continuously measured. Immediately thereafter, subjective evaluation of feelings was performed using a modified semantic differential (SD) method. The results showed that visual stimulation with forest imagery induced (1) a significant decrease in oxy-Hb concentrations in the right prefrontal cortex and (2) a significant increase in perceptions of feeling "comfortable," "relaxed," and "natural."

Physiological effects of viewing fresh red roses.

OBJECTIVES: The present study aimed to clarify the effects of viewing fresh roses on prefrontal cortex activity, autonomic nervous activity and subjective assessments of psychological relaxation. DESIGN: A crossover design, in which each experimental group crosses over from one treatment to another, was used. SETTING AND INTERVENTIONS: A total of 15 female university students (mean age 21.7±1.1years) viewed fresh roses for 3min; the control consisted of no experimental stimulus. MAIN OUTCOME MEASURES: Physiological effects on prefrontal cortex activity were determined by near-infrared time-resolved spectroscopy, which was assessed by measuring oxyhemoglobin (oxy-Hb) concentration in the left and right prefrontal cortex; effects on autonomic nervous activity were assessed by measuring heart rate variability (HRV) and heart rate. Modified semantic differential method and Profile of Mood States were used to determine subjective evaluations. RESULTS: Viewing roses induced: 1) a significant decrease in oxy-Hb concentrations in the right prefrontal cortex; 2) a marginally significant decrease in ln[LF/(LF+HF)] of HRV, which is associated with sympathetic nervous activity; 3) a significant increase in perceptions of feeling 'comfortable,' 'relaxed,' and 'natural;' and 4) a significant improvement in mood state. CONCLUSIONS: These findings indicate that visual stimulation with roses induces physiological and psychological relaxation.