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Nature Experience Reduces Rumination and Subgenual Prefrontal Cortex Activation
Figure 1. The impact of nature experience on self-reported rumination and blood perfusion to the sgPFC. (A) Change in self-reported rumination (postwalk minus prewalk) for participants randomly assigned to take a 90-min walk either in a natural setting or in an urban setting. (B) A time-by-environment interaction in blood perfusion was evident in the sgPFC. F map of significant interactions at a threshold of P < 0.05, FWE corrected for multiple comparisons. (C) Change in blood perfusion (postwalk minus prewalk) for participants randomly assigned to take a 90-min walk either in a natural setting or in an urban setting. Error bars represent SE within subjects: *P < 0.05, ***P < 0.001. Significance More than 50% of people now live in urban areas. By 2050 this proportion will be 70%. Urbanization is associated with increased levels of mental illness, but it’s not yet clear why. Through a controlled experiment, we investigated whether nature experience would influence rumination (repetitive thought focused on negative aspects of the self), a known risk factor for mental illness. Participants who went on a 90-min walk through a natural environment reported lower levels of rumination and showed reduced neural activity in an area of the brain linked to risk for mental illness compared with those who walked through an urban environment. These results suggest that accessible natural areas may be vital for mental health in our rapidly urbanizing world. Abstract Urbanization has many benefits, but it also is associated with increased levels of mental illness, including depression. It has been suggested that decreased nature experience may help to explain the link between urbanization and mental illness. This suggestion is supported by a growing body of correlational and experimental evidence, which raises a further question: what mechanism(s) link decreased nature experience to the development of mental illness? One such mechanism might be the impact of nature exposure on rumination, a maladaptive pattern of self-referential thought that is associated with heightened risk for depression and other mental illnesses. We show in healthy participants that a brief nature experience, a 90-min walk in a natural setting, decreases both self-reported rumination and neural activity in the subgenual prefrontal cortex (sgPFC), whereas a 90-min walk in an urban setting has no such effects on self-reported rumination or neural activity. In other studies, the sgPFC has been associated with a self-focused behavioral withdrawal linked to rumination in both depressed and healthy individuals. This study reveals a pathway by which nature experience may improve mental well-being and suggests that accessible natural areas within urban contexts may be a critical resource for mental health in our rapidly urbanizing world. Related Media Nature May Be Key to Strengthening Our Attention (November 28, 2023) Stanford researchers find mental health prescription: Nature (June 30, 2015)
Read moreSafeguarding Human Health in the Anthropocene Epoch
Figure 1: Services provided by natural systems. Adapted from the Millennium Ecosystem Assessment. Far-reaching changes to the structure and function of the Earth’s natural systems represent a growing threat to human health. And yet, global health has mainly improved as these changes have gathered pace. What is the explanation? As a Commission, we are deeply concerned that the explanation is straightforward and sobering: we have been mortgaging the health of future generations to realise economic and development gains in the present. By unsustainably exploiting nature’s resources, human civilisation has flourished but now risks substantial health effects from the degradation of nature’s life support systems in the future. Health effects from changes to the environment including climatic change, ocean acidification, land degradation, water scarcity, overexploitation of fisheries, and biodiversity loss pose serious challenges to the global health gains of the past several decades and are likely to become increasingly dominant during the second half of this century and beyond. These striking trends are driven by highly inequitable, inefficient, and unsustainable patterns of resource consumption and technological development, together with population growth. We identify three categories of challenges that have to be addressed to maintain and enhance human health in the face of increasingly harmful environmental trends. Firstly, conceptual and empathy failures (imagination challenges), such as an over-reliance on gross domestic product as a measure of human progress, the failure to account for future health and environmental harms over present day gains, and the disproportionate effect of those harms on the poor and those in developing nations. Secondly, knowledge failures (research and information challenges), such as failure to address social and environmental drivers of ill health, a historical scarcity of transdisciplinary research and funding, together with an unwillingness or inability to deal with uncertainty within decision making frameworks. Thirdly, implementation failures (governance challenges), such as how governments and institutions delay recognition and responses to threats, especially when faced with uncertainties, pooled common resources, and time lags between action and effect. Although better evidence is needed to underpin appropriate policies than is available at present, this should not be used as an excuse for inaction. Substantial potential exists to link action to reduce environmental damage with improved health outcomes for nations at all levels of economic development. This Commission identifies opportunities for action by six key constituencies: health professionals, research funders and the academic community, the UN and Bretton Woods bodies, governments, investors and corporate reporting bodies, and civil society organisations. Although better evidence is needed to underpin appropriate policies than is available at present, this should not be used as an excuse for inaction. Substantial potential exists to link action to reduce environmental damage with improved health outcomes for nations at all levels of economic development. This Commission identifies opportunities for action by six key constituencies: health professionals, research funders and the academic community, the UN and Bretton Woods bodies, governments, investors and corporate reporting bodies, and civil society organisations. Depreciation of natural capital and nature’s subsidy should be accounted for so that economy and nature are not falsely separated. Policies should balance social progress, environmental sustainability, and the economy. To support a world population of 9–10 billion people or more, resilient food and agricultural systems are needed to address both undernutrition and overnutrition, reduce waste, diversify diets, and minimise environmental damage. Meeting the need for modern family planning can improve health in the short term—eg, from reduced maternal mortality and reduced pressures on the environment and on infrastructure. Planetary health offers an unprecedented opportunity for advocacy of global and national reforms of taxes and subsidies for many sectors of the economy, including energy, agriculture, water, fisheries, and health. Regional trade treaties should act to further incorporate the protection of health in the near and long term. Several essential steps need to be taken to transform the economy to support planetary health. These steps include a reduction of waste through the creation of products that are more durable and require less energy and materials to manufacture than those often produced at present; the incentivisation of recycling, reuse, and repair; and the substitution of hazardous materials with safer alternatives. Despite present limitations, the Sustainable Development Goals provide a great opportunity to integrate health and sustainability through the judicious selection of relevant indicators relevant to human wellbeing, the enabling infrastructure for development, and the supporting natural systems, together with the need for strong governance. The landscape, ecosystems, and the biodiversity they contain can be managed to protect natural systems, and indirectly, reduce human disease risk. Intact and restored ecosystems can contribute to resilience (see panel 1 for glossary of terms used in this report), for example, through improved coastal protection (eg, through wave attenuation) and the ability of floodplains and greening of river catchments to protect from river flooding events by diverting and holding excess water. The growth in urban populations emphasises the importance of policies to improve health and the urban environment, such as through reduced air pollution, increased physical activity, provision of green space, and urban planning to prevent sprawl and decrease the magnitude of urban heat islands. Transdisciplinary research activities and capacity need substantial and urgent expansion. Present research limitations should not delay action. In situations where technology and knowledge can deliver win–win solutions and co-benefits, rapid scale-up can be achieved if researchers move ahead and assess the implementation of potential solutions. Recent scientific investments towards understanding non-linear state shifts in ecosystems are very important, but in the absence of improved understanding and predictability of such changes, efforts to improve resilience for human health and adaptation strategies remain a priority. The creation of integrated surveillance systems that collect rigorous health, socioeconomic, and environmental data for defined populations over long time periods can provide early detection of emerging disease outbreaks or changes in nutrition and non-communicable disease burden. The improvement of risk communication to policy makers and the public and the support of policy makers to make evidence-informed decisions can be helped by an increased capacity to do systematic reviews and the provision of rigorous policy briefs. Health professionals have an essential role in the achievement of planetary health: working across sectors to integrate policies that advance health and environmental sustainability, tackling health inequities, reducing the environmental impacts of health systems, and increasing the resilience of health systems and populations to environmental change. Humanity can be stewarded successfully through the 21st century by addressing the unacceptable inequities in health and wealth within the environmental limits of the Earth, but this will require the generation of new knowledge, implementation of wise policies, decisive action, and inspirational leadership.
Read moreThe Benefits of Nature Experience: Improved Affect and Cognition
Figure 2. Affective impact of nature experience. Difference scores are used to compare performance from before the walk to performance afterward (negative values indicate a decrease after the walk, while positive values indicate an increase). Each panel depicts these difference scores for the urban and nature groups separately on one of the four affective measures: (A) anxiety, (B) rumination, (C) negative affect, and (D) positive affect. Error bars depict standard error (SE) values. Highlights Nature experience produced clear benefits for affect (e.g., decrease in anxiety and rumination). Nature experience produced some benefits for cognition (complex working memory span task). Supports the idea that exposure to natural greenspace can improve affect and cognition. This study investigated the impact of nature experience on affect and cognition. We randomly assigned sixty participants to a 50-min walk in either a natural or an urban environment in and around Stanford, California. Before and after their walk, participants completed a series of psychological assessments of affective and cognitive functioning. Compared to the urban walk, the nature walk resulted in affective benefits (decreased anxiety, rumination, and negative affect, and preservation of positive affect) as well as cognitive benefits (increased working memory performance). This study extends previous research by demonstrating additional benefits of nature experience on affect and cognition through assessments of anxiety, rumination, and a complex measure of working memory (operation span task). These findings further our understanding of the influence of relatively brief nature experiences on affect and cognition, and help to lay the foundation for future research on the mechanisms underlying these effects. Related Media Nature May Be Key to Strengthening Our Attention (November 28, 2023)
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