Recent research indicates that people who spend at least two hours a week in nature are more likely to report good health and high levels of wellbeing than those who spent no time in nature \cite{White_2019}. Furthermore, these findings were consistent across a variety of demographic variables including sex, age-group, occupational social grade, presence of chronic illness and whether or not individuals met physical activity guidelines. Prior research had indicated that spending time in nature over a 2-week period boosts hedonic as well as eudaimonic wellbeing \cite{howell2014}, and that effect sizes are larger (ds from .37 to .63) than those reported for other positive psychology interventions (ds from .20 to .34) \cite{Bolier_2013}. Exposure to nature can lead to transcendent emotions \cite{Bethelmy_2019}, peak experience \cite{1964} and psychological flow \cite{Csikszentmihalyi_2014}. Interestingly, transcendent emotions - including compassion, gratitude and awe - foster healthy social relationships \cite{Stellar_2017} and such relationships are facilitated by spending time in nature \cite{Mayer_2008,Richardson_2016}. Research also reports that exposure to nature is associated with stress reduction \cite{Hansmann_2007,Ulrich_1991}, feelings of restoration \cite{White_2013,Wyles_2017}, subjective wellbeing \cite{Johansson_2011,LUCK_2011,White_2017}, and improved cognitive functioning \cite{Berman_2008,Berto_2005}.

Human beings have a strong, innate affiliation with the biological world, a phenomenon captured by the ‘biophilia hypothesis’. The related ‘topophilia hypothesis’ emphasises emphasises affiliation with the local environment (‘place’) and a role for cultural experience \cite{Beery_2015,s2012}. The word topophilia combines topos (place) with philia (love) and was first used by the poet W.H. Auden in 1947. Unfortunately, the experience of topophilia is increasingly being replaced by the experience of 'tierratrauma' (acute trauma associated with rapid and devastating change to a loved place) and 'solastalgia' (chronic place-based distress)  \cite{albrecht2019}.

The biophilia and topophilia hypotheses provide a foundation on which to understand the distress, pain or sickness associated with environmental degradation of home or territory. Glenn Albrecht, an Australian environmental philosopher coined the term ‘solastalgia’ after reflecting on the environmental impacts of open cut coal mining and pollution of local power stations on the residents of the Upper Hunter Region of NSW in Australia. He writes that ‘solastalgia’ reflects a “specific form of melancholia connected to a lack of solace and intense desolation” associated with place-based distress \cite{albrecht2005a}. Psychiatric disorders are also expected to arise from the direct and indirect effects of climate-related disasters through disruption to food supply and damage to community wellbeing \cite{Berry_2009,Hayes_2018}. In fact, the number of people experiencing psychological trauma following a disaster exceeds those with physical injury by 40–1 \cite{j2007}, and weather related disasters have increased by 44% since the year 2000 \cite{Watts_2018}. Critically, there is now strong evidence to conclude that we humans are contributing to such change, a phenomenon known as anthropogeneic climate change. Research reporting on ratings of peer-reviewed climate-science and self-ratings by climate change scientists themselves has indicated that there is 97% endorsement of humans contribution to the warming climate \cite{Cook_2013,Cook_2016}. Unfortunately, this finding remains under appreciated in a brave new world of alternative facts and disinformation \cite{Lewandowsky_2013,Lewandowsky_2017}.

In our original GENIAL model \cite{Kemp_2017}, we described an important role for positive social ties and community on health and wellbeing. Interestingly, others \cite{Beery_2015,Nurse_2010} have argued that the boundaries of ‘community’ should be extended to the environment including soil, water, plants and animals, in order to facilitate love and respect, and a commitment to environmental sustainability. Feelings of guilt, shame, fear, emotional discomfort and solastalgia have been associated with motivation to engage in environmental sustainability behaviours \cite{Albrecht_2007,DICKERSON_1992,Kaiser_2008,Malott_2010}. Others have proposed an ‘aesthetics of elsewhere’, which involves encouraging a double aesthetic judgment of ‘here’ and ‘elsewhere’ to induce an aesthetic melancholia to influence consumption decisions \cite{maskit2011}. Researchers have begun to investigate the positive psychology of sustainability \cite{Corral_Verdugo_2014,Corral_Verdugo_2012,obrien2016}, a strategy that may help to foster what has been described as sustainable wellbeing \cite{Kjell_2011}. In a study on 606 undergraduate students in Mexico \cite{fraijo-sing2011}, researchers reported that pro-ecological, altruistic, frugal and equitable behaviors reflect the sustainably-oriented person, and that these behaviours have positive psychological consequences. Prior research had shown that individuals engaging in pro-ecological behaviours – such as resource conservation – report greater happiness \cite{Brown_2005}, that altruism leads to greater long-term happiness \cite{ja1995}, and that frugality predicts greater psychological wellbeing, satisfaction and motivation \cite{Brown_2005}. More equitable individuals however, are reported to be less happy due to the ‘negative hedonic impact of inequality in society’ as climate change exacerbates existing inequities \cite{Hayes_2018}.

Others have proposed the concept of ‘sustainable happiness’ \cite{2016}, defined as “happiness that contributes to individual, community, and/or global well-being without exploiting other people, the environment, or future generations”\cite{obrien2010} thus differentiating it from phrases typically used in positive psychology such as “sustaining happiness” or “sustainable increases in happiness” \cite{s2007}. More recently, a structural model of the relationships between character strengths, virtues and sustainable behaviours has been presented such that all 24 character strengths \cite{p2004} are associated with all four sustainable behaviours (i.e. altruistic, frugal, equitable and pro-ecological behaviours) \cite{Corral_Verdugo_2015}. This body of work provides a useful foundation on which psychological scientists may advocate a role for their discipline in addressing environmental challenges, because pro-environmental behaviours also provide opportunities to promote happiness and build resources for resilience, in addition to much-needed environmental benefits \cite{Clayton_2016,fraijo-sing2011,Corral_Verdugo_2012}. The grave threat of anthropogenic climate change may also inspire a variety of positive feelings such as altruism, compassion, optimism as well as a sense of purpose “as people band together to salvage, rebuild, and console amongst the chaos and loss of a changing climate” \cite{Hayes_2018}, feelings that reflecting ‘active hope’ \cite{c2012}.

While the emerging positive psychology of sustainability \cite{Corral_Verdugo_2015,Kjell_2011,Corral_Verdugo_2012,obrien2016} provides a clear link between individual and environmental wellbeing, it is also notable that the vast majority of people do not engage in pro-environmental behaviours, a result of helpless and low self-efficacy \cite{Salomon_2017}. The difficulty in comprehending problems associated with climate change, and the intangibility and invisibility of such change may also lead individuals to sit on their hands and do nothing, a phenomenon known as ‘Giddens Paradox’ \cite{a2009}. Recent qualitative research \cite{langen2017} has investigated the psychological processes that foster these pro-environmental behaviours. Findings were interpreted in the context of ‘salutogenesis’ \cite{ANTONOVSKY_1996}, which emphasises a role for a ‘sense of coherence’ for managing and overcoming stress. This ‘sense of coherence’ reflect feelings of confidence that stimuli in the (internal and external) environment are comprehensible, manageable and meaningful. The researchers reported that grassroots activists relied on values and attitudes, emphasising that the problems are so vast that limits are imposed on knowledge (i.e. comprehensibility), arguing that emotions are a key mediator between the appraisal of a situation and motivation to take action. A sense of personal responsibility for change was associated with an improved perceived quality of life, attributable to empowerment and social cohesion, which provides a sense of meaning and purpose in life. Concrete and collective action was also observed to enhance positive emotions and mastery experiences subsequently enhancing beliefs about self-efficacy (i.e. manageability) \cite{langen2017}.

In summary, exposure to nature provides a host of benefits that have direct impacts on wellbeing - over and above the beneficial impacts of outdoor physical activity \cite{Franco_2017,Capaldi_2015,Bowler_2010} - and may even promote commitment to pro-environmental behaviours. We have observed emerging research interest in the concepts of sustainable happiness and wellbeing, directly linking positive psychology to concepts relating to sustainability and pro-environmental behaviours.

The GENIAL framework illustrates common pathways to ill-health and ill-being versus health and wellbeing. The evidence-base for these pathways - including a key regulatory role for vagal function - have been described previously \cite{Kemp_2017,Kemp2017,ah2018}. While our original GENIAL model highlighted the importance of positive social ties for individual health and wellbeing \cite{Kemp_2017}, our updated model (see Fig \ref{div-162276})  provides an important update to our original GENIAL model, emphasising individual, community and environmental contributors to personal wellbeing. In doing so, our model characterises the relationships between individuals, communities and their environments, as well as the impacts of sociostructural factors and their impact on the health and wellbeing of the individual. Key features of the individual, community and environmental domains are now briefly described with a particular focus on vagal function.

Individual wellbeing is promoted through positive psychological experiences and positive health behaviours. Meta-analyses have demonstrated that positive psychological interventions (PPIs) are effective for people with or without diagnosed disorders \cite{Bolier_2013,Hendriks_2019,Chakhssi_2018,Sin_2009,White_2019a}, with effect sizes ranging from small to large. Meta-analyses have further demonstrated the effectiveness of specific positive psychological interventions (PPIs) on increasing SWB, PWB, optimism, positive affect and life satisfaction, including the practicing of gratitude \cite{Davis_2016}, the ‘best possible self’ intervention \cite{Malouff_2016}, savouring positive emotions \cite{Smith_2014}, mindfulness-based interventions \citep{Simpson_2019}, and performing acts of kindness \cite{Curry_2018}. The three main models of wellbeing \cite{Seligman_2018,Diener_1984,Ryff_1995} provide a theoretical foundation for developing new and novel interventions for enhancing positive psychological experience. Importantly, research demonstrates that despite the different theories that have been proposed for wellbeing, each of these contributes to the same higher order construct of wellbeing \cite{Goodman_2017,Disabato_2016}. In other words, there are many strategies through which positive psychological experience may be enhanced. Our recent review on vagal function \cite{Kemp_2017a} concluded that higher resting state vagal function is associated with positive mood states, highlighting the utility of positive psychology interventions for enhancing a key upstream regulator of health and wellbeing. It is interesting to note that that purpose in life has also been shown to predict allostatic load ten years later \cite{Zilioli_2015}as measured by the sum of seven scores across multiple physiological systems including cardiovascular, lipid, glucose metabolism, inflammation, autonomic function, and hypothalmic-pituitary-adrenal risk scores. Unfortunately however, this study did not distinguish between upstream and downstream systems driving increases in metabolic risk (i.e. vagal function plays a known regulatory role over inflammatory processes, as demonstrated previously: \citealt{Tracey_2002}). 

Focusing on health behaviours - including exercise, diet and sleep - typically involves consideration of one’s physical health, however recent research has also highlighted the impact of positive health behaviours on mental wellbeing, supporting declarations that there can be no health without mental health \cite{Vladu_2016}. On a sample of 49 unique prospective studies (N=266,939), physical activity was shown to protect against depression, irrespective of age and geographic region \cite{Schuch2018}. In a cross-sectional study of more than 1 million individuals in the U.S. \cite{Chekroud2018}, exercisers displayed 43% fewer days of poor mental health than non-exercisers. The authors further reported that all exercise types were associated with a lower mental health burden (from 11.8% to 22.3% reduction), and the activities associated with the largest associations included popular  team  sports  (22.3%  lower),  cycling  (21.6%  lower),  and  aerobic  and  gym  activities  (20.1%  lower). Exercise duration of  45  minutes  and  frequencies  of  three  to  five  times  per week were associated with the lowest mental health burden. With respects to diet, the Mediterranean diet has received a large focus in regards to its link with health conditions, for example, combined data from four longitudinal studies found a risk estimate of highest vs. lowest adherence to the Mediterranean diet of 0.67 (95% CI 0.55-.82) for incident depression \cite{Lassale_2018}. With regards to sleep, a systematic review and meta-analysis of 14 studies found sleep disturbances significantly predicted the risk of suicidal ideation; an effect not moderated by depression \cite{Liu_2019}. Critically, each of these health behaviours - physical activity, diet and sleep - have a powerful impact on vagal function \cite{Kemp2017}. As vagal function provides a structural link between physical and mental health, focus on positive health behaviours is a powerful means to promote health and wellbeing.

In addition to focusing on psychological experience and health behaviours, recent developments in psychological science have highlighted a key role for social relationships for the health and wellbeing of the individual. Therefore, individual wellbeing may also be promoted by focusing on community, the focus of our original GENIAL model \cite{Kemp_2017}. The implications of social relationships for the health and wellbeing of the individual were recently summarised in the recent publication of 'The New Psychology of Health: Unlocking the Social Cure' \cite{2018}. \citet{Haslam_2016} evaluated a new intervention that targets social isolation and disconnection, "Groups 4 Health" (G4H). Results highlighted the intervention to improve mental health, wellbeing, and social connectedness up to 6-months post intervention. In addition to this, improvements in depression, anxiety, stress, loneliness, and life satisfaction correlated with increased identification with the G4H group and with multiple groups. The work by Barbara Fredrickson and colleagues is also relevant here, emphasising the upward spiral of positive emotions, social connectedness and vagal function \cite{Kok_2010,Kok_2013}. We build on previous research such as this, incorporating well established theories of vagal function, such as the polyvagal theory \citep{Porges:2011wv,PORGES_1995,Porges_2001,Porges_2003,Porges_2007} to highlight the importance of vagal function in health and wellbeing. 

Finally, our updated model emphasises the environmental context within which individual health and wellbeing is promoted and communities reside. Glenn Albrecht \cite{albrecht2019} provides a solid foundation for understanding the link between human emotion and the environment, coining numerous words to emphasise the negative and positive 'psychoterratic' states that have important implications for the health and wellbeing of individuals, communities and societies now and into the future. Environmental contributors include negative and positive psychoterratic states such as solastalgia (chronic place-based distress) and soliphila (a neutral political term for combatting solastalgia) \cite{albrecht2019}. A review of the literature on potential mechanisms linking nature to health identified 21 potential pathways empirically linked to nature \cite{Kuo_2015}. These pathways included environmental factors including phytoncides - antimicrobial volatile organic compounds with physiological effects - and vegetation filtering of pollutants, physiological factors such as elevation of vagal function and immune function, psychological factors involving positive emotions and attention restoration, and behavioural factors including positive health behaviours such as the promotion of physical activity and social ties. Interestingly, this paper suggested that enhanced immune functioning might reflect a central pathway for mediating the beneficial effects of nature on health. It is apparent however, that vagal function plays a regulatory role over immune function via the cholinergic anti-inflammatory response \citep{Pavlov_2003}. Thus, we suggest here that vagal function will play a key role in not only regulating the beneficial effects of positive psychological experience, positive health behaviours, positive social ties, but also, the beneficial effects of nature on human health and wellbeing.  

In conclusion, our updated GENIAL model (fig \ref{div-162276}) summarises individual, community and environmental contributors to human health and wellbeing. Our model also characterises the major clinical targets for potentially improving the wellbeing in people living with a host of chronic conditions and disorders, a topic to which we turn next. Clinical targets include psychological experience, health behaviour, social connections and outdoor nature-based activities to which the tools from positive psychology and behaviour change may be applied. We examine how clinicians might implement and sustain positive change in our discussion on facilitating behaviour change in section \ref{225494}.