Changes in Psychological and Cognitive Outcomes after Green versus Suburban Walking: A Pilot Crossover Study

How Does Nature Exposure Affect Adults With Symptoms of Mental Illness? A Meta-Analysis

Existing research on the effects of nature exposure on the mental health of adults indicates that spending time in nature reduces depressive symptoms and stress, increases quality of life and mood and improves mental health. This meta-analysis aimed to answer the question: what are the effects of nature exposure on the social, mental and physical health of adults with symptoms of mental illness? The meta-analysis included all studies relevant to the study research questions which collected quantitative data on nature exposure using validated instruments for at least two time points on each participant and which were published between 1990 and 2020. Regarding the impact of nature exposure on adults with symptoms of mental illness, analyses showed significant, moderate effect sizes for all studies and smaller, but significant, effect sizes for studies with control groups Analyses also yielded critical information regarding the effect size of the type of nature dosage, nature setting, nature-based activity, key mental health outcomes and other factors. These findings from the present study results have important implications regarding the potential benefits of nature exposure for adults and its role in healthcare.

Current methodologies of greenspace exposure and mental health research-a scoping review

Introduction

Greenspaces can provide an important resource for human mental health. A growing body of literature investigates the interaction and the influence of diverse greenspace exposures. In order to gain a comprehensive understanding of the complex connection between greenspace and mental health, a variety of perspectives and methodological combinations are needed. The aim of this review is to assess the current methodologies researching greenspace and mental health.

Methods

A scoping review was conducted. Four electronic databases (Pubmed, Embase, PsycInfo, Web of Science) were searched for relevant studies. A wide range of greenspace and mental health keywords were included to provide a comprehensive representation of the body of research. Relevant information on publication characteristics, types of greenspaces, mental health outcomes, and measurements of greenspace exposure and mental health was extracted and assessed.

Results

338 studies were included. The included studies encompassed a multitude of methods, as well as outcomes for both greenspace and mental health. 28 combinations were found between seven categories each for greenspace and mental health assessment. Some pairings such as geoinformation systems for greenspace assessment and questionnaires investigating mental health were used much more frequently than others, implying possible research gaps. Furthermore, we identified problems and inconsistences in reporting of greenspace types and mental health outcomes.

Discussion

The identified methodological variety is a potential for researching the complex connections between greenspace and mental health. Commonly used combinations can provide important insights. However, future research needs to emphasize other perspectives in order to understand how to create living environments with mental health benefits. For this purpose, interdisciplinary research is necessary.

Do Mental Health Changes in Nature Co-occur with Changes in Heartrate Variability and Executive Functioning? A Systematic Review

PURPOSE OF REVIEW

Given the global burden of mental health issues, new solutions are needed to promote mental health. Nature exposure represents a promising option to promote mental health, but the mechanisms are poorly understood. Recent frameworks have argued that changes in mental health in nature are caused by activity changes in the vagus nerve, which connects the heart and the brain, and that these changes also improve executive functioning (EF) abilities. This suggests that changes in mental health symptomology in nature should be accompanied by changes in vagus nerve activity, as well as changes in executive functioning. Yet, little work has systematically examined co-variation of these outcomes in empirical studies. The present manuscript systematically examines whether changes in mental health in nature are accompanied by changes in vagus nerve activity (approximated by heartrate variability) and changes in executive functioning.

RECENT FINDINGS

There is compelling evidence that spending time in nature can increase heartrate variability, improve mental health, and improve executive functioning. However, despite strong theoretical claims that these three outcomes should be linked after spending time in nature settings, few studies directly examine such co-occurrence. The study systematically examines whether studies that considered both mental health and executive functioning (n = 6) showed co-occurring effects in response to nature exposure. Similarly, the study also considers if studies examining mental health and heartrate variability (n = 6) showed similarly directional effects following nature exposure. This systematic review concludes with discussion about the limited number of studies (n =1) that include all three measures. We find mixed results of co-occurrence with these variables, suggesting that the relationship between these three constructs in nature may be more nuanced than current theory suggests. Perhaps more importantly, our results demonstrate that there is very little existing work linking changes in mental health to changes in EF and vagal tone. We conclude with justification for why it may be beneficial for researchers to include all three metrics as well as guidance on how to do so.

A systematic review of the anxiety-alleviation benefits of exposure to the natural environment

Research suggests that exposure to natural environments can be beneficial for health, such as reducing physical illness and improving mood and cognitive ability. The potential benefits of nature have come into focus at a time when mental health issues are growing globally. Here, we have selected 24 studies from four databases for meta-analysis to explore the effects of exposure to the natural environment on the anxiety of the human body and summarize the influencing factors on the anxiety relief effect. A random-effect meta-analysis of anxiety state changes before and after exposure to natural environment shows that natural exposure effectively alleviated human anxiety (SMD -1.28, 95% CI: -1.65 to -0.92). The overall quality of the included papers, assessed using the PEDro scale, is considered to vary considerably, but most of the papers are rated between 4 and 7 which is considered fair or good. In addition, we have also investigated the potential moderators of anxiety-relieving effects of the nature. Our results shows that the age and exposure time of the subjects are related to the effect of anxiety relief. The results of the subgroup analysis of moderators prove that compared with the middle-aged people (SMD -0.63, 95% CI: -1.13 to -0.12), young people (SMD -1.50, 95% CI: -1.90 to -1.10) get better anxiety alleviation effect in the natural environment. In terms of exposure time, compared with 0.5-2 h (SMD -0.18, 95% CI: -0.59 to -0.23) and >2 h (SMD -0.84, 95% CI: -1.40 to -0.27) exposure periods, subjects get the maximum anxiety relief benefit when they spent <0.5 h (SMD -1.60, 95% CI: -1.93 to -1.27) in the natural environment. However, the quality of the included studies varies greatly and there is a significant heterogeneity in the meta-analysis. Study location, natural environment type and other moderator factors have no obvious correlation with anxiety-alleviation effect of the nature. A higher quality and more comprehensive study needs to be carried out to find out more moderators about the effects of the natural environment on anxiety alleviation. Further experimental studies should also be conducted to determine the mechanism by which natural exposure reduces anxiety so as to provide strong support for the construction and improvement of healthy natural environment.

Residential green space improves cognitive performances in primary schoolchildren independent of traffic-related air pollution exposure

BACKGROUND

Cognitive performances of schoolchildren have been adversely associated with both recent and chronic exposure to ambient air pollution at the residence. In addition, growing evidence indicates that exposure to green space is associated with a wide range of health benefits. Therefore, we aimed to investigate if surrounding green space at the residence improves cognitive performance of primary schoolchildren while taking into account air pollution exposure.

METHODS

Cognitive performance tests were administered repeatedly to a total of 307 primary schoolchildren aged 9-12y, living in Flanders, Belgium (2012-2014). These tests covered three cognitive domains: attention (Stroop and Continuous Performance Tests), short-term memory (Digit Span Forward and Backward Tests), and visual information processing speed (Digit-Symbol and Pattern Comparison Tests). Green space exposure was estimated within several radii around their current residence (50 m to 2000 m), using a aerial photo-derived high-resolution (1 m²) land cover map. Furthermore, air pollution exposure to PM_2.5 and NO₂ during the year before examination was modelled for the child's residence using a spatial-temporal interpolation method.

RESULTS

An improvement of the children's attention was found with more residential green space exposure independent of traffic-related air pollution. For an interquartile range increment (21%) of green space within 100 m of the residence, a significantly lower mean reaction time was observed independent of NO₂ for both the sustained-selective (-9.74 ms, 95% CI: -16.6 to -2.9 ms, p = 0.006) and the selective attention outcomes (-65.90 ms, 95% CI: -117.0 to -14.8 ms, p = 0.01). Moreover, green space exposure within a large radius (2000 m) around the residence was significantly associated with a better performance in short-term memory (Digit-Span Forward Test) and a higher visual information processing speed (Pattern Comparison Test), taking into account traffic-related exposure. However, all associations were attenuated after taking into account long-term residential PM_2.5 exposure.

CONCLUSIONS

Our panel study showed that exposure to residential surrounding green space was associated with better cognitive performances at 9-12 years of age, taking into account traffic-related air pollution exposure. These findings support the necessity to build attractive green spaces in the residential environment to promote healthy cognitive development in children.

The effects of forest bathing on psychological well-being: A systematic review and meta-analysis

Globally, around half (55%) of the population live in fast-paced urban settings where many people find it challenging to manage their stress and respond to crises with a positive mindset. This resulted in prolonged distress where anxiety and fatigue caused physical and mental health concerns. Nature walks involving immersive exposure in the forest, and green spaces have been posited to offer physiological and psychological benefits. Therefore, in this systematic review, we evaluated the effects of forest bathing on psychological and physiological outcomes. We searched four English and five non-English databases (Chinese and Korean) for peer-reviewed studies published between January 2000 and March 2021. This review adhered to the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-analysis Statement 2020. The primary outcomes explored in this review were mainly psychological, including anxiety, depression, mood and quality of life. The secondary outcomes were physiological outcomes such as blood pressure and heart rate. We conducted a meta-analysis on each outcome using the random-effects model. Heterogeneity was assessed by the I² statistic. Thirty-six articles (21 in English, 3 in Chinese and 12 in Korean) with 3554 participants were included in this review. Our meta-analysis suggested that forest bathing can significantly reduce symptoms of depression and anxiety. However, we did not observe as many benefits in physiological outcomes. Against the background of the negative effects of urbanization on mental well-being, this review highlighted the potential therapeutic role of forests in the contemporary world, lending further evidence-based support for forest conservation.

Psychological benefits of outdoor physical activity in natural versus urban environments: A systematic review and meta-analysis of experimental studies

The impact of environmental context on the psychological benefits derived from physical activity has attracted research attention in recent years. Previous reviews have compared effects of indoor versus outdoor exercise. This review compares the effects of physical activity undertaken in outdoor green natural environments versus outdoor urban environments on psychological health outcomes in adult general populations. An electronic literature search identified 24 experimental studies meeting the inclusion criteria. Results were analysed via narrative synthesis (n = 24) and meta-analysis (n = 9) of effect on six outcomes. Narrative synthesis found in favour of the natural environment for anxiety, anger/hostility, energy, affect and positive engagement. Post-intervention effect sizes suggested duration and social context as potential moderators. The meta-analyses revealed large or moderate effects in favour of the natural environment for anxiety, fatigue, positive affect and vigour, and a small effect for depression. Results were subject to high risk of bias and heterogeneity. Physical activity undertaken outdoors in natural environments is more beneficial for a range of psychological outcomes compared with urban environments. The various effect sizes evident in the meta-analyses may be explained by differing mechanisms through which psychological gains are experienced during physical activity in nature.

Women Emotional, Cognitive and Physiological Modes of Coping with Daily Urban Environments: A Pilot Study

Studies on the effect of urban environments on human risk to health and well-being tend to focus on either physiological or cognitive and emotional effects. For each of these effects, several indicators have been proposed. They are determined either by a physiological-emotional theory or by a cognitive theory of direct attention. However, the interrelationships between these indices have not been thoroughly investigated in environmental contexts. Recently, a neuro-visceral model that incorporates all three aspects has been proposed. The present article focuses on understanding the mechanism of coping with urban environments. More specifically, we analyze the interrelations among nine of the more commonly used indices that represent the physiological, emotional and cognitive aspects of coping with urban environments. The data were collected in the following four environments: home, park, city center and residential area. The participants were 72 healthy, middle-class mothers with either high school or postgraduate education. They wherein their fertile age (20-35) with average Body Mass Index (BMI) of 22.2 and S.D. of 0.8 (48 Arab Muslims and 24 Jewish). They were recruited in a snowball method. Path analysis and principal component analysis are used in order to identify the interrelations among the physiological, cognitive and emotional indices and the directions of these interrelations. According to the findings, the Autonomic Nervous System (ANS), as measured by Heart Rate Variability (HRV) and primarily the parasympathetic tone (High frequency-HF) is the pivotal mechanism that modulates emotional and cognitive responses to environmental nuisances. The ANS response precedes and may trigger the emotional and the cognitive responses, which are only partially interrelated. It appears that the autonomic balance measured by Standard Deviation of NN interval (SDNN) and HF, the cognitive index of restoration and the emotional indices of discomfort and relaxation are closely interrelated. These seemingly disparate operands work together to form a comprehensive underlying network that apparently causes stress and risk to health in urban environments while restoring health in green environments.

Cognitive-Emotional Benefits of Weekly Exposure to Nature: A Taiwanese Study on Young Adults

Empirical evidence of nature’s benefits to cognitive and emotional well-being is emerging. In this study, 48 Taiwanese young adults (24 indoors and 24 outdoors in urban greenspace) completed four weekly 45 min exposure sessions. The study explores whether the outdoor group surpasses the indoor group in cognitive and emotional well-being and nature connectedness. There were no significant differences for the indoor group across different measurements of rumination and connectedness to nature. However, the outdoor group displayed a significant reduction in rumination post-test compared to the one week prior and the first session. Similarly, for sessions two, three, and four and one month post-test, the outdoor group’s connectedness to nature was significantly higher than pre-test. Specific autobiographical memory was enhanced while overgeneral autobiographic memory was reduced during the third and fourth sessions, though these changes were not sustained at one-month follow-up. Surprisingly, both groups yielded similar results in decreased depression, anxiety, and stress. A significantly higher number of outdoor group participants had employed nature exposure for coping with stress or emotions after the program. We discuss the implications of this for counseling services for young adults and highlight future research possibilities, including formulating a nature-exposure protocol and a program evaluation for consolidating evidence-based nature prescription.

Nature-based outdoor activities for mental and physical health: Systematic review and meta-analysis

Mental health problems are associated with lower quality of life, increased unscheduled care, high economic and social cost, and increased mortality. Nature-based interventions (NBIs) that support people to engage with nature in a structured way are asset-based solutions to improve mental health for community based adults. However, it is unclear which NBIs are most effective, or what format and dose is most efficacious. We systematically reviewed the controlled and uncontrolled evidence for outdoor NBIs. The protocol was registered at PROSPERO (CRD42020163103). Studies that included adults (aged ≥18 years) in community-based settings with or without mental and/or physical health problems were eligible for inclusion. Eligible interventions were structured outdoor activities in green and/or blue space for health and wellbeing. We searched ASSIA, CENTRAL, Embase, Greenfile, MEDLINE, PsycINFO, and Web of Science in October 2019; the search was updated in September 2020. We screened 14,321 records and included 50 studies. Sixteen studies were randomised controlled trials (RCTs); 18 were controlled studies; and 16 were uncontrolled before and after studies. Risk of bias for RCTs was low to moderate; and moderate to high for controlled and uncontrolled studies. Random effects meta-analysis of RCTs showed that NBIs were effective for improving depressive mood -0.64 (95% CI: 1.05 to -0.23), reducing anxiety -0.94 (95% CI: 0.94 to -0.01), improving positive affect 0.95 (95% CI: 0.59 to 1.31), and reducing negative affect -0.52 (95% CI: 0.77 to -0.26). Results from controlled and uncontrolled studies largely reflected findings from RCTs. There was less evidence that NBIs improved physical health. The most effective interventions were offered for between 8 and 12 weeks, and the optimal dose ranged from 20 to 90 min. NBIs, specifically gardening, green exercise and nature-based therapy, are effective for improving mental health outcomes in adults, including those with pre-existing mental health problems.

Impact of Exposure to Natural and Built Environments on Positive and Negative Affect: A Systematic Review and Meta-Analysis

There is increasing evidence that the natural environment provides substantial benefits to human emotional well-being. The current study synthesized this body of research using the meta-analysis and assessed the positive and negative effects of exposure to both the natural and built environments. We searched four databases and 20 studies were included in the review. The meta-analysis results showed the most convincing evidence that exposure to the natural environment could increase positive affect (standardized mean difference, SMD = 0.61, 95% CI 0.41, 0.81) and decreased negative affect (SMD = -0.47, 95% CI -0.71, -0.24). However, there was extreme heterogeneity between the studies, and the risk of bias was high. According to the subgroup analysis, study region, study design, mean age of the sample, sample size, and type of natural and built environment were found to be important factors during exposure to the natural environment. The implications of these findings for the existing theory and research are discussed. These findings will help convince the health professionals and policymakers to encourage the residents to increase their time spent in the natural environment. These findings of this systematic review also suggested that the creation, maintenance, and enhancement of accessible greenspaces or existing natural environments may form part of a multidimensional approach to increasing emotional well-being of the local populations.

There's no place like home? The psychological, physiological, and cognitive effects of short visits to outdoor urban environments compared to staying in the indoor home environment, a field experiment on women from two ethnic groups

BACKGROUND

The home environment is regarded as a safe, comfortable environment, however, home can also be a stressful place. Compared to staying in the indoor home environment, the effects of short visits to outdoor urban environments on short-term psychological, physiological and cognitive responses were not studied previously.

AIM

To evaluate whether visits to different urban and ethnic environments, in comparison to staying in the home indoor environment, leads to short-term changes in psychological, physiological and cognitive responses and whether these responses are independent of ethnicity.

METHODS

The participants, 20-35 year-old healthy women (N = 72, 48 Arab and 24 Jewish), started the experiment at their home and visited six different outdoor urban environments in predominantly ethnic Arab or Jewish cities, in Israel. First they visited intra-ethnic city and afterward inter-ethnic city environments. In each city they first visited an urban park and afterward, in a random order, a residential neighborhood and the city center. In each environment (including home) the following measures were used to evaluate psychological, physiological and cognitive effects: mood (measured as positive and negative emotions, cheerfulness, relaxed, natural and discomfort feelings), autonomic nervous system balance (assessed using heart rate variability (HRV)) and working memory (measured by a backwards digit-span task). Several potential mediators were measured: carbon monoxide (CO), heat, noise, social aspects, and the self-perceived restoration scale.

RESULTS

Compared to staying in the indoor home environment, short visits to outdoor urban environments, specifically intra and inter-ethnic parks, were associated with beneficial psychological, physiological, and cognitive responses, and the strongest effects were found for the intra-ethnic park. The results for the other urban environments were different between Jewish and Arab women. The self-perceived restoration, social aspects and reduced CO, heat and noise exposures during the visits did not explain the observed changes between the outdoor environments and home.

CONCLUSIONS

Visits to urban parks compared to staying in the home environment had beneficial short-term changes in psychological, physiological, and cognitive responses, regardless of ethnicity. The changes could not be attributed to the investigated mediators. Women should be encouraged to go outdoors and specifically visit parks to improve their psychological and physiological health.

Study of active neighborhoods in Detroit (StAND): study protocol for a natural experiment evaluating the health benefits of ecological restoration of parks

BACKGROUND

Individuals living in deprived inner cities have disproportionately high rates of cancers, Type 2 diabetes and obesity, which have stress- and physical inactivity-related etiologies. This study aims to quantify effects of ecological park restoration on physical activity, stress and cardio-metabolic health outcomes.

METHODS

The Study of Active Neighborhoods in Detroit is a quasi-experimental, longitudinal panel natural experiment with two conditions (restored park intervention (INT) and control (CNT)) and annual measurements at baseline and 3-years post-restoration. Individuals (sampled within 500 m of an INT/CNT park) serve as the unit of analysis. Restoration (n = 4 parks) involves replacing non-native plants and turf with native plants; creating trails; posting signage; and leading community stewardship events. The CNT condition (n = 5) is an unmaintained park, matched to INT based on specified neighborhood conditions. Recruitment involves several avenues, with a retention goal of 450 participants. Park measures include plant/avian diversity; usage of the park (SOPARC); signs of care; auditory environment recordings; and visual greenness using 360 imagery. Health outcomes include device-based physical activity behavior (primary outcome); salivary cortisol (secondary outcome); and several downstream health outcomes. Exposure to the INT will be assessed through visual contact time and time spent in the park using GPS data. Changes in health outcomes between years and INT versus CNT will be tested using generalized linear (mixed) models.

DISCUSSION

Our study will examine whether restored urban greenspaces increase physical activity and lower stress, with public health planning implications, where small changes in neighborhood greenspaces may have large health benefits in low-income neighborhoods.

STUDY REGISTRATION

Registration: OSF Preregistration registered March 31, 2020. Accessible from https://osf.io/surx7.

Affective Outcomes of Group versus Lone Green Exercise Participation

'Green exercise' (being physically active within a natural environment) research has examined the influence of environmental setting on health and wellbeing-related exercise outcomes. However, it is not known whether social exercise settings influence green exercise-associated changes in mood, self-esteem, and connection to nature. This study directly compared outcomes of participating in green exercise alone compared to in a group. Using repeated measures, counterbalanced and randomized-crossover design, participants (n = 40) completed two 3 km runs around sports fields. These fields had a relatively flat grass terrain, predominant view of trees, and open grassland. On one occasion participants ran alone and on the other they ran in a group of 4-5 participants. Questionnaire measures of mood, self-esteem, and connection to nature were completed immediately pre- and post-run. Across all of the measures, two-way mixed ANOVAs found that there were statistically significant effects for time but not for time-by-condition interactions. The simplest interpretation of this finding is that social setting does not influence individuals' attainment of the psychological outcomes of green exercise participation. However, we discuss the possibility that more complex processes might underpin this finding.

Walking Green: Developing an Evidence Base for Nature Prescriptions

Although the health benefits of exercise and exposure to nature are well established, most evidence of their interaction comes from acute observations of single sessions of activity. However, documenting improved health outcomes requires ongoing interventions, measurement of multiple outcomes, and longitudinal analyses. We conducted a pilot study to guide the development of a protocol for future longitudinal studies that would assess multiple physiological and psychological outcomes. Herein, we report psychological outcomes measured from thirty-eight participants before and after three conditions: a 50 min walk on a forest path, a 50 min walk along a busy road, and a period of activities of daily living. Changes in positive and negative affect, anxiety, perceived stress, and working memory are reported. We benchmark these results to existing studies that used similar protocols and also identify elements of the protocol that might impair recruitment or retention of subjects in longer-term studies. Linear mixed-models regression revealed that walking improved psychological state when compared to activities of daily living, regardless of walk environment (p < 0.05). Comparison of mean differences showed that forest walks yielded the largest and most consistent improvements in psychological state. Thus, despite a protocol that required a 3.5 h time commitment per laboratory visit, the beneficial effects of walking and exposure to a forested environment were observed.