Elizabeth Lines is a health promotion consultant with particular interests in mental health, and health and well-being in later life.
Rates of depression and other stress-related chronic diseases continue to climb, adding to our increasing health care costs. There is urgency everywhere to find ways to cut costs and stem the tide. The facts are:
- Total annual health care spending in Canada is now over $200 billion (CIHI, 2012); in Ontario, health care spending consumes over 40 percent of the provincial budget. Finding ways to contain health care spending is a priority.
- Depression is the leading cause of disability worldwide (WHO, 2012) and a leading contributor to the economic burden of disease.
- Chronic stress is pervasive, and related to depression and the development of chronic disease.
Can nature help? Research findings suggest that natural settings such as parks, wilderness areas, urban green spaces and gardens may be just what the doctor ordered to improve both physical and mental health and reduce the load on our health care system.
For one thing, green space provides an opportunity for physical activity, which contributes directly to physical health and, through biophysiological mechanisms, enhances mental well-being. That much is well established. But there is also a growing collection of evidence suggesting that exposure to natural settings has direct positive effects, independent of physical activity, on reducing stress levels and enhancing mental well-being. The capacity of the natural environment to improve the physical and mental health of the population and reduce health care expenditures is attracting the interest of health practitioners and policy-makers everywhere. Such a prescription for health also empowers citizens to take greater control of their own health and well-being, most often with few costs attached.
The research literature on the relationship of nature to physical and mental health is extensive and growing. This report offers a brief review of recent research examining the impacts of natural environments specifically on mental health and well-being.
Background: Connections to Nature
The idea that nature and healing are linked is an ancient one, as reflected by expressions such as “Communing with nature is good for the soul.” In fact, on the timescale of history, the inherent healing properties of nature have only recently been challenged by the development of Western science and technology, particularly the field of medicine (Abkar, Kamal, Maulan, and Mariapan, 2010). An emphasis on the spiritual and emotional strength available through a close relationship with nature is still embraced by First Nations and aboriginal communities, and retains an intuitive appeal with deep resonance across time and cultures.
A number of theories based on evolution have been offered to elucidate the human connection to nature. Hartig, van den Berg, Hagerhall, Tomalak, et al. (2010) have provided a concise overview of several of these. In general, they attempt to account for what seems to be a universal attraction to and appreciation of natural environments that would favour survival. Key theories include, among others, the Biophilia Hypothesis (Fromm, 1964; Wilson, 1984), the Savannah Theory (Orians, 1980), and the Prospect-Refuge Theory (Appleton, 1975). These all posit an innate basis for our environmental preferences, which then are assumed to serve as a marker for environmental conditions associated with survival.
Complementary to these population-level accounts are theories that operate at the individual level and help to further explain the psycho-physiological mechanisms through which natural environments have their physical and mental benefits. These “restoration and recovery” theories suggest that natural settings that once favoured the physical survival of the species still provide health benefits through processes such as attention restoration and psycho-physiological stress recovery.
Attention Restoration Theory (ART), originally developed in the 1980s (Kaplan and Kaplan, 1989), is often used to account for the positive mental health and well-being effects of nature. The theory holds that “nature provides the particular environmental stimuli to allow restoration from attention fatigue, which occurs during the performance of cognitive tasks that require prolonged maintenance of directed attention” (Bowler, Buyung-Ali, Knight, and Pullin, 2010, p. 2). A psycho-evolutionary theory proposed by Ulrich (1983) is in keeping with ART, suggesting that “nature may allow psychophysiological stress recovery through innate, adaptive responses to attributes of natural environments such as spatial openness, the presence of pattern or structure, and water features” (ibid, p. 2) and that these features promote positive emotions related to safety and survival. Ulrich’s theory is sometimes referred to as the Stress Reduction/Recovery Theory (SRT). These two theoretical orientations have helped to direct much of the research examining the possible mental health and stress-related impacts of nature.
As earlier noted, this “natural” relationship between nature and health effects has received increasing research attention in recent years. If nature is indeed the best medicine, the repercussions could do wonders for the health of the natural environment and the population, as well as the overburdened health care system. But what is the evidence? Settings/contexts under study have ranged from the simple viewing of nature, through being in nature, to engaging in various physical pursuits in natural environments. A variety of terms such as nature, natural environments, natural settings and green space are often used interchangeably in the literature. In practice, much of the research has been conducted in urban green spaces such as city parks and green campuses; a preponderance of research participants have been university students; most measures are self-reports or physiological measures; and most of the studies are designed as pre-/post-intervention measurements recording immediate and long-term outcomes.
Viewing Nature Has Positive Effects
Results from a number of studies support the idea that both physical healing and stress recovery are facilitated by viewing a natural scene. Maller, Townsend, Pryor, Brown and St. Leger (2005) describe several such studies that range across populations and settings. For example, Ulrich (1984) found that hospital patients who could view the outdoors through a window recover from surgery faster than those with restricted views; that students who watched a stressful film recovered faster in a natural setting (Ulrich, 1991); and that prisoners with a view of nature show stress symptoms less frequently (Moore, 1981). The ability to view a natural scene may also enhance attention and improve job satisfaction (Kaplan and Kaplan, 1989). Maller, Townsend, St. Leger, et al. (2008) also refer to studies that indicate mood is improved by viewing nature. They note that simple observation is itself an activity and one that appears to offer restorative impacts (pp. 10–11).
Viewing nature is positive for health, particularly in terms of recovering from stress, improving concentration and productivity, and improving the psychological state, particularly of people in confined circumstances such as prisons, hospitals, and high-rise apartments/high-density living (ibid, p. 11).
Abkar et al. (2010) provide a similar review of the evidence and stress the implications for urban planners and architects, particularly those working on institutional buildings for confined populations.
Being in Nature
Parks provide an increasingly important opportunity for experiencing the natural environment, since 80 percent of Canadians now live in urban settings. In terms of daily life as well as research settings, the experience of being in nature is often being in a park. Godbey (2009) cites both self-report and biological data (e.g., cortisol levels) as evidence that spending time in urban parks is related to decreased stress. Bowler et al. (2010), in a systematic review of studies comparing effects on well-being after exposure to a natural environment (e.g., a park, a green campus) compared with a synthetic environment (e.g., a gymnasium) concluded that the natural environment may promote direct, positive benefits independent of activity (a walk or a run). The predominant types of outcomes measured included emotions, attention, and biological markers (such as those for cardiovascular, endocrine or immune function). The analysis found evidence of “beneficial changes on feelings of energy, anxiety, anger, fatigue and sadness” (p. 6) associated with the natural environment. The majority of study participants were college students and active adults, usually men.
De Vries, Verheij, Groenewegen and Spreeuwenberg (2003), using a large health data set and environmental data in Netherlands, found evidence that living in proximity to green space is positively related to self-reported health, including indicators of mental health (de Vries et al., 2003; van den Berg, 2010). Findings from a questionnaire completed by over 900 residents of several Swedish towns and cities suggest that levels of stress were inversely related to the amount of time spent in urban open green spaces (Grahn and Stigsdotter, 2003). Furthermore, the amount of time spent in green spaces was greater if green spaces were close by. Of interest, too, was that having immediate access to a yard or garden was also related to lower stress levels.
A Swedish study of the rehabilitative impact of nature on crisis response found that the simple experience of being in nature was most rehabilitative for those experiencing the highest levels of stress. Walking in nature also had a positive effect, though the difference was not as great. For those experiencing low-to-moderate stress levels, social interactions in the natural setting contributed more to stress reduction (Ottoson and Grahn, 2008).
The results of this study also suggest that the cumulative positive effects of the natural environment may promote greater resilience in the face of life crises. Similar results found by Grahn and Stigsdotter (2003) applied regardless of sex, socioeconomic level or age. “Our results suggest that nature functions as a type of remedy, aid, resource or catalyst. If people in crisis have many nature experiences, they tend to experience an improved state of health” (Ottosson and Grahn, 2008, p. 66).
Nature Has Positive Impacts on Attention
A number of studies across populations and settings have disclosed positive influences of nature on attention (Kuo and Faber Taylor, 2004). “‘Nature’ experienced in a wider variety of forms — including wilderness backpacking, gardening, viewing slides of nature, restoring prairie ecosystems, and simply having trees and grass outside one’s apartment building — has been linked to superior attention, effectiveness, and effectiveness-related outcomes” (p. 1580). Some findings suggest that the benefits to attention of walking in parks are greatest for those with the greatest deficits. Along with attention improvements, walking in nature as opposed to an urban setting reduced anger, improved positive affect, and reduced blood pressure (Hartig, Evans, Jamner, et al., 2003).
Interest in the restorative impacts of natural settings on attention has driven study into the potential benefit of exposure to natural environments for children with attention deficits (ADD/ADHD), and researchers have attempted to delineate the type of natural setting most conducive to improvement. For example, in their 2008 study, Faber Taylor and Kuo compared the impacts on attention behaviours of children with ADHD who were taken on guided walks in three different outdoor areas: a park setting, a downtown area and a residential area. The extent of positive experience (as measured by parents’ perceptions) and degree of improvements in attention behaviours were greater after the park experience.
Green Exercise and Mental Health
Given evidence that both physical activity and natural environments can promote positive psychological states, some scientists have studied whether exposure to a natural environment while exercising leads to greater mental health benefits than activity done elsewhere.
To investigate the potentially synergistic benefits of combining a natural setting with physical exercise, Pretty, Peacock, Sellens and Griffin (2005) compared the effects on study subjects of viewing photographs of nature settings or urban scenes projected onto a wall while running on a treadmill. There were two versions of each setting: pleasant and unpleasant. There was also a control group not exposed to an image while running. The image of the pleasant urban setting actually included urban green space within it. In the end, the pleasant images of both rural and urban settings had positive impacts on self-esteem beyond the effects of exercise alone, indicating a synergistic effect. The effects on mood were also positive, though not as consistent.
Roe and Aspinall (2011) compared the restorative benefits of walking in rural and urban settings for adults with either good or poor mental health and found that restorative benefits, based on cognitive and affective measures, were generally greater for both groups in the rural setting. Also, similar to the findings of Ottosson and Grahn (2008), those with poorer mental health showed the greatest gains.
In a systematic review of 11 studies comparing the effects of activity (walking or running) in an outdoor natural versus indoor environment, Thompson Coon, Boddy, Stein, et al. (2011) found that many of the self-report findings suggested greater improvements to mental well-being (moods, feelings) from outdoor than indoor activity. Benefits included “greater feelings of revitalization and positive engagement, decreases in tension, confusion, anger, and depression, and increased energy.… Participants reported greater enjoyment and satisfaction with outdoor activity and declared a greater intent to repeat the activity at a later date” (p. 1761). However, the authors caution that these measures were taken following single episodes of exercise, with unknown effects on adherence; moreover, methodologies tended to be weak and varied, making it difficult to compare results and interpret findings. Participants again were usually young adults, with an average age of 25 years.
Analyzing existing population data (n = 1,890 persons aged 16 and older) from a 2008 Scottish Health Survey, Mitchell (2012) examined frequency of use of natural settings for (unspecified) physical activity in relation to outcomes on two measures, one of mental health and one of well-being. He concludes that regular physical activity in natural settings does offer more protection against poor mental health than activity in other settings, but the association was not as clear with mental well-being. Of the natural environments specified, woodlands and parks appeared to be the most beneficial to mental health, with regular users experiencing about half the risk of poor mental health than non-users. The findings also point to the possibility that being active in a natural environment even once a week might be sufficient for positive benefits.
While the Mitchell findings suggest physical activity in nature on a once-a-week basis could bring benefits, an analysis of data from 10 studies measuring the impact of green exercise on self-esteem and mood indicated that large benefits could be achieved with very little time investment. In fact, the largest gains were observed within the first five minutes of activity. Taken together, these studies represented a range of population characteristics, and of exercise intensity and duration. The greatest self-esteem improvements occurred in the young and in those with mental illness (Barton and Pretty, 2010); men showed greater mood improvement than did women.
The potential positive effects of physical activity on depression are quite well established, but less is known about the impacts of exercise context for this population. Robertson, Robertson, Jepson and Maxwell (2012) present a systematic review and meta-analysis of eight randomized controlled trials in which participants representing a range of ages, settings and severity of depression participated in a walking intervention outdoors, indoors or in combination. Of interest, outdoor walking interventions showed positive effects for women with postpartum depression (Armstrong and Edwards, 2003, 2004); another showed similar benefits for older women who were overweight, depressed, or both (Gusi, Reyes, Gonzalez-Guerrero, et al., 2008).
In a study of 19 participants with major depressive disorder (MDD), improvements were observed in both short-term memory capacity and in affect following a 50-minute nature walk versus an urban walk (Berman, Kross, Krpan, et al., 2012). There were again indications that these participants benefited more from the nature-walk intervention than did a healthy population in an earlier study. That is, those with significant deficits/needs seemed to gain the most. Results point to nature walks as an inexpensive and generally accessible adjunct to the treatment regimens currently in use for MDD.
Although the preponderance of findings pointing to nature’s positive effects on mental health is impossible to ignore, additional research is needed. The question of the frequency, duration and intensity of exposure required for benefit is in need of ongoing rigorous study, with close attention to subgroups of the population. Moreover, little is known of the long-term effects of exposure to or activity in nature, especially in relation to details of the exposure itself. Too, the social factors that often accompany experiences in natural settings are important to consider as mitigating circumstances related to outcomes. The big question is: What are the essential requirements for, and the limits of, green healing?
Increasingly, the promise of green healing is being carried into practice, even as research continues. Green exercise, when conducted as a therapeutic intervention for depression or anxiety, is but one component of a growing field termed green care. Green care includes a number of possible interventions, such as animal-assisted therapies, horticultural therapy and ecotherapy (Sempik, Hine, and Wilcox [eds.], 2010). For example, Discovery Quest is a well-known walking and nature therapy program in England that has shown positive results (Hine, Wood, Barton, and Pretty, 2011).
Within the field of green care, recent work on the benefits of gardens and of particular garden designs for people with Alzheimer disease and dementia is showing great promise: Findings suggest a decrease in negative behaviours. Those who engage in gardening activities may demonstrate improved confidence and social skills. Contact with nature has also been shown to reduce agitation and improve sleep and hormonal balance. These results, representing the outcomes of several studies, are summarized on the University of Washington’s Green Cities: Good Health website.
The concept of ecotherapy is in itself an exciting development, as it represents a commitment to the health of the population and the environment, and so has the potential to unite the environmental movement with health and health promotion interests. Ecotherapy can be defined as:
…an umbrella term for all nature-based methods aimed at the re-establishment of human and ecosystem reciprocal well-being; a transdisciplinary and ecosystemic approach aimed at the collaborative enhancement of physical, psychological and social health for people, communities and ecosystems. These outcomes are achieved through the development of a close personal and collective relationship with the natural ecosystem. (Sempik et al., 2010, p. 44)
Ecotherapy is one example of the ways in which the growing evidence base supporting the value of natural settings for well-being is likely to prompt greater ecological awareness and environmental care (Hartig, Kaiser, and Bowler, 2001), creating synergies between environmental, physical and psychological health.
The truth is, day-to-day life is increasingly distant from natural settings. According to 2011 census data, more than 86 percent of Ontarians live in urban areas. Meanwhile, the natural environment continues to be degraded or eliminated by advancing urban and suburban sprawl, commercial/industrial land use and climate change; natural settings are disappearing. The challenges are great. But, perhaps the mounting evidence that a “dose” of nature is good for health will contribute to the preservation and maintenance of the natural environment, as well as directly improve quality of life and reduce the health care burden.
There are indications that this is beginning to happen. Some governments are developing national nature strategies in an attempt to improve the physical and mental health of their populations, reduce the strain on health care budgets, and support efforts to maintain natural spaces. Thus, for example, we see the Natural England program, a government initiative to protect and improve England’s natural environment and encourage people to enjoy and get involved in their surroundings, operating in conjunction with Walk England, and the Nordic countries’ Environmental Action Plan 2005–2008 and the Outdoor Life and Mental Health project (2006).
Many research questions and practical challenges remain, including the ongoing need to motivate the population to action (Berman et al., 2012). But despite existing gaps and weaknesses in the knowledge base, the evidence is in: Green is good for our health, body and mind alike.
Discovery Quest Community Project is an award-winning walking and nature therapy program, running since 2006 in Norfolk, England, for community members experiencing serious mental illness. Although led by mental health practitioners, nature-focused partner organizations provide environmental and conservation opportunities. Participants meet weekly over a 6-month period and experience the challenges and exhilaration of exploring their natural environment during their 10–16 km walk (6–10-miles) each session. A University of Essex evaluation concluded that most participants completing the program had improved self-esteem, communication skills and overall psychological well-being (Hine, Wood, Barton & Pretty, March 2011). An eight-page information booklet (in .PDF format) is available on the website, detailing the program elements.
Mind, a national mental health charity in the UK, has called for a green agenda for mental health (Ecotherapy, 2007; available on Mind’s Ecotherapy Web page). Through a grants program called Ecominds, it has funded a range of 130 environmental projects across England to promote an ecotherapeutic approach to mental health and well-being. Projects include, for example, walking groups, habitat restoration, and horticultural and agricultural activities. Details and contacts for individual project sites are available on the website.
Nature Clubs for Families Tool Kit: Do It Yourself! Do It Now!
Available for download at www.childrenandnature.org.
As the title suggests, this toolkit from the Children & Nature Network is designed to help groups of adults with children connect with nature, and with each other. The kit contains ideas, tips, examples of flyers and record-keeping forms. The site also contains links to related resources.
University of Essex Green Exercise Website
This site presents the green-exercise research and evaluation agenda at the University of Essex, a leader in the field. This university is where the concept of “green care” was introduced — essentially, the therapeutic application of green exercise and other nature-based interventions such as Wilderness Therapy and Care Farming.
Green Care: A Conceptual Framework
A Report of the Working Group on the Health Benefits of Green Care
COST 866, Green Care in Agriculture, April 2010, 119 pages
This comprehensive yet concise report is produced by the European Cooperation in Science and Technology (COST) network. It helps to frame the concept of green care in relation to a number of existing social and psychological constructs, therapeutic theories and applied approaches to mental health and well-being. While green care does include a range of nature-based activities, the reader is reminded that “everything that is green is not ‘green care’.”
Therapeutic Nature Design for Dementia Care
Dr. Garuth Chalfont of Sheffield, England, specializes in the field of therapeutic nature design as a landscape architect, writer and presenter and has produced a number of books and guides to assist others in “how to establish a therapeutic program of nature-based activity for people with dementia living in nursing and residential-care settings or attending day support facilities.” He offers the term dementia green care to describe the work, intended to improve the quality of life of people living with dementia or distressed behaviours by helping them to connect to the natural world. Several publications are available as downloads (.PDF format) from this site, including their Project Booklet and Design Guide, key outcomes of a Therapeutic Dementia Care Research and Design Project, funded by the NHS.
Walk England is a social enterprise responsible for a number of walking projects across England, including Walk London, Walk4life, and the Green Exercise Project. See Downloads at the foot of the home page for a growing array of useful tools, including a series of how-to guides such as “How to Organize a Walking Event” and “How to Lead a Walk.”
Green Exercise is a joint project of conservation and mental health charities, along with the Walk England projects . It is operating in three areas of England: Doncaster, Hastings and Norwich. Aimed at those who are at increased risk for mental health problems, the project includes walking and the opportunity to participate in conservation activities. The site links to the projects and describes the activities at each.
Abkar, M., Kamal, M.S., Maulan, S., & Mariapan, M. (2010). Influences of viewing nature through windows. Australian Journal of Basic and Applied Sciences, 4(10), 5346–5351.
Appleton, J. (1975). The Experience of Landscape. Wiley, London. Cited in Hartig, et al. (2010).
Armstrong, K., & Edwards, H. (2003). The effects of exercise and social support on mothers reporting depressive symptoms: A pilot randomized controlled trial. International Journal of Mental Health Nursing, 12, 130–138. Cited in Robertson, et al. (2012). doi:1046/j.1440-0979.2003.00229.x
Armstrong, K., & Edwards, H. (2004). The effectiveness of a pram-walking exercise programme in reducing depressive symptomatology for postnatal women. International Journal of Nursing Practice, 10(100), 177–194. Cited in Robertson, et al. (2012). doi:1111/j.1440-172X.2004.00478.x
Barton, J., & Pretty, J. (2010). What is the best dose of nature and green exercise for improving mental health? A multi-study analysis. Environmental Science and Technology, 44, 3947–3955.
Berman, M.G., Kross, E., Krpan, K.M., Askren, M.K., Burson, A., Deldin, P.J., Kaplan, S., Sherdell, L., Gotlib, I.H., & Jonides, J. (2012). Interacting with nature improves cognition and affect for individuals with depression. Journal of Affective Disorders, doi:10.1016/j.jad.2012.03.012
Bowler, D.E., Buyung-Ali, L.M., Knight, T.M., & Pullin, A.S. (2010). A systematic review of evidence for the added benefits to health of exposure to natural environments. BMC Public Health, 10(10), 456, www.biomedcentral.com
Canadian Institute for Health Information (CIHI). (2012). Canada’s Health Care Spending Growth Slows, www.cihi.ca
Chalfont, G.E., & Rodiek, S. (2005). Building Edge: An Ecological Approach to Research and Design of Environments for People with Dementia. Alzheimer's Care Today, 6(4), 341.
de Vries, S., Verheij, R., Groenewegen, H., & Spreeuwenberg, P. (2003). Natural environments—healthy environments? An exploratory analysis of the relationship between green space and health. Environment and Planning, 35(10), 1717–1731.
Faber Taylor, A. & Kuo, F.E. (2008). Children with attention deficits concentrate better after walk in the park. Journal of Attention Disorders Online First, 2008 (August 25), doi:10.1177/1087054708323000
Fromm, E. (1964). The Heart of Man. Harper and Row, New York. Cited in Hartig, et al. (2010).
Godbey, G. (May 2009). Outdoor Recreation, Health, and Wellness: Understanding and Enhancing the Relationship. Discussion paper prepared for the Outdoor Resources Review Group, Resources for the future background study, RFF DP 09-21, www.rff.org
Grahn, P., & Stigsdotter, U.A. (2003). Landscape planning and stress. Urban Forestry and Urban Greening, 2, 1–18.
Gusi, N., Reyes, M.C., Gonzalez-Guerrero, J.L., Herrera, E., & Garcia, J.M. (2008). Cost-utility of a walking programme for moderately depressed, obese, or overweight elderly women in primary care: A randomised controlled trial. BMC Public Health, 8(88), 231, doi:10.1186/1471-2458-8-231 Cited in Robertson, et al. (2012).
Hartig, T., Kaiser, F.G., & Bowler, P.A. (2001). Psychological restoration in nature as a positive motivation for ecological behavior. Environment and Behavior, 33(4), 590–607.
Hartig, T., Evans, G.W., Jamner, L.D., Davis, D.S., & Garling, T. (2003). Tracking restoration in natural and urban field settings. Journal of Environmental Psychology, 23, 109–123.
Hartig, T., van den Berg, A.D., Hagerhall, M., Tomalak, M., Bauer, N., Hansmann, R., Ojala, A., Syngollitou, E., Carrus, G., van Herzele, A., Bell, S., Camilleri Podesta, M.T., & Waaseth, G. (2010). Chapter 5 in: Nilsson Kl, Sangster, M., Gallis, C., Hartig, T., De Vries, Sl, Seeland, K. & Schipperijn, J., Forest, Trees and Human Health. Dordrecht: Springer Science Business and Media.
Hine, R., Wood, C., Barton, J., & Pretty, J. (2011, March). The mental health and well-being effects of a walking and outdoor activity based therapy project. A report for Discovery Quest and Julian Housing. Interdisciplinary Centre for Environment and Society (ICES), University of Essex.
Kaplan, R., & Kaplan, S. (1989). The Experience of Nature: A Psychological Perspective. Cambridge University Press, Cambridge. Cited in Hartig, et al. (2010).
Kuo, F., & Faber Taylor, A. (2004). A potential natural treatment for attention-deficit/hyperactivity disorder: Evidence from a national study. American Journal of Public Health, 94(9): 1580–1586.
Maller, C., Townsend, M., Pryor, A., Brown, P., & St. Leger, L. (2005). Healthy nature, healthy people: ‘Contact with nature’ as an upstream health promotion intervention for populations. Health Promotion International, 21(1), 45–54, doi:10.1093/heapro/dai032
Maller, C., Townsend, M., St. Leger, L., Henderson-Wilson, C., Pryor, A., Prosser, L., & Moore, M. (2008). Healthy parks, healthy people: the health benefits of contact with nature in a park context. Melbourne, Australia: Deakin University and Parks Victoria.
Mitchell, R. (2012). Is physical activity in natural environments better for mental health than physical activity in other environments? Social Science & Medicine, doi:10.1016/j.socscimed.2012.04.012
Mooney, P., & Nicell. P.L. (1992). The importance of exterior environment for Alzheimer residents: Effective care and risk management. Healthcare Management Forum 5(2), 23–29. Cited in Wolf & Flora (2010).
Moore, E.O. (1981). A prison environment’s effect on health care service demands. Journal of Environmental Systems, 11, 17–34. Cited in Maller, et al. (2005).
Orians, G.H. (1980). Habitat selection: General theory and applications to human behavior. In: Lockard, J.S. (ed.). The Evolution of Human Social Behavior. Elsevier, New York, pp. 49–66. Cited in Hartig, et al. (2010).
Ottosson, J., & Grahn, P. (2008). The role of natural settings in crisis rehabilitation: How does the level of crisis influence the response to experiences of nature with regard to measures of rehabilitation? Landscape Research, 33(1), 51–70.
Pretty, J., Peacock, J., Sellens, M., Griffin, M. (2005). The mental and physical health outcomes of green exercise. International Journal of Environmental Health Research, 15(5), 319–337.
Rappe, E. (2005). The Influence of a Green Environment and Horticultural Activities on the Subjective Well-Being of the Elderly Living in Long-Term Care. University of Helsinki, Department of Applied Biology. Cited in Wolf & Flora (2010).
Robertson, R., Robertson, A., Jepson, R., Maxwell, M. (2012). Walking for depression or depressive symptoms: A systematic review and meta-analysis. Mental Health and Physical Activity, 5, 66-75, doi:10.1016/j.mhpa.2012.03.002
Roe, J., & Aspinall, P. (2011). The restorative benefits of walking in urban and rural settings in adults with good and poor mental health. Health and Place, 17, 103–113.
Sempik, J., Hine, R., & Wilcox, D. (eds.). (2010). Green Care: A Conceptual Framework, A Report of the Working Group on the Health Benefits of Green Care. COST Action 866, Green Care in Agriculture, Loughborough: Centre for Child and Family Research, Loughborough University.
Thompson Coon, J., Boddy, K., Stein, K., Whear, R., Barton, J., & Depledge, M.H. (2011). Does participating in physical activity in outdoor natural environments have a greater effect on physical and mental well-being than physical activity indoors? A systematic review. Environmental Science and Technology, 45, 1761–1772.
Ulrich, R.S. (1983). Aesthetic and affective response to natural environment. In: Altman, I., & Wohlwill, J.F. (eds.). Behavior and the Natural Environment. Plenum, New York, pp. 85–125. Cited in Hartig, et al. (2010).
Ulrich, R. S. (1984). View through a window may influence recovery from surgery. Science, 224, 420–421. Cited in Maller, et al. (2005).
Ulrich, R. S., Simons, R. F., Losito, B. D., Fiorito, E., Miles, M. A., & Zelson, M. (1991b). Stress recovery during exposure to natural and urban environments. Journal of Environmental Psychology, 11, 231–248. Cited in Maller, et al. (2005).
Ulrich, R.S. (2002). Health benefits of gardens in hospitals. In: Plants for People, Proceedings of the International Exhibition Floriade. Cited in Wolf & Flora (2010).
Wolf, K.L., & Flora, K. (2010). Mental health and function: A literature review. In: Green Cities: Good Health. College of the Environment, University of Washington, http://depts.washington.edu/hhwb/Thm_Mental.html
van den Berg, A., Maas, J., Verheij, R.A., & Groenewegen, P.P. (2010). Green space as a buffer between stressful life events and health. Social Science & Medicine, 70(8), 1203–1210.
Wilson, E.O. (1984). Biophilia: The Human Bond with Other Species. Cambridge, MA: Harvard University Press. Cited in Hartig, et al. (2010).
World Health Organization (WHO). (2012, October). Depression. Fact Sheet No. 369.