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. Other meta-analyses on health behaviours have emphasised the role of physical activity \cite{Chekroud2018}, diet \cite{Firth_2019} and sleep \cite{Baglioni_2016} on our mental lives. 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 critical regulator of health and wellbeing. Our work further emphasises the structural link between the vagus nerve, and physical and mental health \cite{Kemp_2017,Kemp2017,ah2018,Kemp_2013,Kemp_2016a}. It is interesting to note here that purpose in life has 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. as we do here. Critically, vagal function plays a known regulatory role over inflammatory processes, as demonstrated previously: \citealt{Tracey_2002}.
In addition to focusing on positive 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 heightened 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}. Other well established theories of vagal function, such as the polyvagal theory \citep{Porges:2011wv,PORGES_1995,Porges_2001,Porges_2003,Porges_2007} highlight a role for the vagus in promoting capacity to engage with others and regulating our emotions during such encounters.
Finally, our updated model emphasises the environmental
context within which individual health and wellbeing is promoted and communities reside. Glenn \citet{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 nations 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}. Other research has shown that vagal function may be facilitated by spending time in nature. For instance, a recent review of the literature \cite{Kondo_2018} on the impacts of spending time outdoors on stress reported that of 17 studies reporting on measures of HRV, 14 reported significant findings. Measures of the high frequency (HF) component - a commonly reported measure of vagal function - increased for participants spending time outdoors. It is relevant to note here that measures of HF HRV are generally negatively correlated with with meaures of heart rate. That is, high levels of vagal function - as is typically indexed by HF HRV - are associated with a low heart rate. Thus, it is against this background of findings that we suggest that vagal function both affects and are affected by the effects of psychological experience, health behaviours, social ties, as well as the environment.
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 targets for potentially improving wellbeing in people including those living with chronic conditions and disorders. 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.