Indeed, there is emerging evidence to suggest that the main environmental risk factors implicated in the increasing prevalence of NCDs, ie. poor diet and sedentary behavior, mediate their effects through immune pathways, with downstream effects on insulin resistance, obesity, cardiovascular disease, as well as mood and behavior. New insights in this rapidly developing field point to the utility of taking population-level primary prevention approaches to both NCDs and CMDs.
We have to say something obesity - now classified as a chronic condition!! I will come back to this.
In an extensive review, Kromhout (2016) concluded that consumption of vegetables and fruit convincingly reduced the risk of coronary heart disease (CHD) and stroke, and on this basis the Dutch food-based dietary guidelines recommended at least 200g of vegetables and 200g of fruit per day.  (Kromhout 2016). This is in keeping with the NHS guidelines which recommends 'five-a-day' (or 400 grams) (UKGOV, 2019), as well as guidance from the World Health Organisation (WHO | Promoting fruit...). Kromhout (2016) also concluded that the consumption of nuts convincingly reduces CHD risk and recommended that one eats at least 15 grams of unsalted nuts per day, although this is not currently recommended in UK guidelines. Also recommended was the consumption of 90 grams of brown or whole-grain products daily, as whole-grain products has been shown to reduce risk of CHD. In contrast to the recommendations by Kromhout et al. (2016), other research suggests that as many as 'ten-a-day' may be required for long-term health benefit (Aune 2017).  Recent studies have demonstrated that the Mediterranean diet may protect against chronic disease including common mental disorders (Lassale et al., 2019; Dinu et al., 2018)Sofi et al. (2010) concluded from a systematic review and meta-analysis that a greater adherence to a Mediterranean diet leads to a significant reduction in cardiovascular incidence, cancer incidence or mortality and neurodegenerative diseases. Importantly, randomised controlled trials now demonstrate that adopting a Mediterranean diet independently reduces cognitive decline associated with chronic conditions (Martínez-Lapiscina et al., 2013; Valls-Pedret et al., 2015). Dietary changes have shown to be effective in triggering changes in the intestinal microbiome (a modulator in the risk of disease development) within 24 hours, highlighting the importance of diet as a pathway through which health can be improved (Singh et al., 2017). It is argued that targeting diet would be an effective opportunity to relieve the growing burden of mental and neurological disease \citep*{Owen_2017}.  This may seem common knowledge, but it has been well established that ‘common knowledge is not common action’ (Swan 2014). For example, a study by Bell et al. (2015) showed that 20% of nursing home residents have been reported to be malnourished internationally, although depending on the definition of malnutrition prevalence ranges from 1.5% to 66.5% (Bell, Lee, and Tamura, 2015). Studies have also shown that improved diet can be effective in improving depression symptomology (Opie et al., 2015; Parletta et al., 2019). An important dietary contributor to risk of future chronic illness is alcohol consumption, which has been causally related to 60 medical conditions, including certain cancers (breast, mouth and liver), epilepsy and haemorrhagic stroke (Room, Babor, and Rehm, 2005). In ‘The 2015 Dutch food-based dietary guidelines’ (Kromhout 2016) claimed that alcohol convincingly increases the risk of stroke and that binge drinking 60 g or more significantly increases the risk of CHD and thus recommends that individuals abstain from alcohol all together or do not drink more than one glass daily. This is roughly in line with the NHS guideline (NHS, 2019)which recommends no more than 2 units a day (this is roughly one pint of beer or a glass of wine). There is mixed evidence as to whether there is a ‘J’ shaped relationship between alcohol and all-cause mortality such that drinking a low amount of alcohol may be more beneficial for health than abstaining from alcohol all together. However, a meta-analysis of 87 studies (Stockwell 2016) adjusted results to account for abstainer bias towards ill health and found no significant reduction in mortality risk for low volume drinkers compared to those who abstain from alcohol. Including former drinkers in the abstainer reference group has biased the drinking risk estimates in many studies. Thus according to these findings, it is best to abstain from alcohol all together as we should not assume there are health benefits to low level drinking. It is acknowledged however, there are other reasons people consume alcohol (e.g. social drinking) and that risk increases with amount drunk.
INSERT two good studies on diet (Med diet):- doi:  10.1002/14651858.CD009825.pub3 - and doi:  10.1002/14651858.CD009825.pub2.
 
Sleep:  Sleep  is an important factor influencing the health and wellbeing of people living with chronic conditions. The International Classification of Sleep Disorders includes more than 80 sleep disorders. Sleep disorders are associated with increased risk of all-cause mortality and serious adverse health consequences \citep{Alvarez_2004}. Epidemiological studies have shown that people with chronic conditions (eg. heart disease, arthritis, diabetes, stroke and lung diseases) had a significantly higher incidences of sleep disturbances than those without such conditions \citep{Foley1999}\citep{Maggi1998}\cite{Vitiello1997}\citep{Foley1995},  \citep{Ancoli-Israel1991}\cite{Foley1999a},  \citep{Whitney1998},  \citep{Newman1997} and \citep{Enright1996}.  The relationship between many chronic conditions and sleep has been shown to be bidirectional; the worsening of one can influence the other (Lee 2012, Ancoli-Israel 2006). Overall there is compelling evidence of the contribution of sleep disorders to the pathogenesis and exacerbation of chronic conditions. In this section we illustrate this point with several examples for the purpose of brevity. We then present evidence exploring the treatment of sleep disorders or they underpinning moderators, which may have the potential to ameliorate the impact of chronic conditions.
Two of the most prevalent sleep disorders, Insomnia and OSA have been shown to contribute to an increased risk of several chronic health conditions (\citep*{Hargens2013} including, but not restricted to, diabetes mellitus \citep{Punjabi2004} and cardiovascular disease \cite{Somers2008}, asthma \citep{Janson1996}, systemic lupus erythematosus \citep{Gudbjörnsson2001}, rheumatoid arthritis \citep{Luyster2011} and inflammatory bowel disease \citep{Keefer2006}. The mechanisms which underpin this relationship are complex and many. However, it is thought that most common sleep disorders result in a reduction of sleep quality and duration which has been associated with increased body weight and adiposity, potentially leading to obesity \citep{López-García2008}\citep{Patel2008}. Although obesity has not yet been classified as a chronic condition in its own right in the UK, it has been formally recognised as such in the United States (references). Nonetheless, it has been well established that obesity significantly contributes to the pathogenesis of many chronic conditions. Consequently, it has been argued that the relationships between chronic conditions and sleep disorders are likely mediated by obesity. For example, with respect to insomnia, \citet{Taheri2004} showed that shorter sleep durations were associated with 15% lower lepin levels and 14.9% higher ghrelin levels which were independent of Body Mass Index (BMI). They concluded that chronically shortened sleep duration could increase appetite leading to overeating and eventually obesity. The neuro-cognitive theory of insomnia suggests that insomnia is associated with increased levels of cortisol \citep{Perlis1997}\citet{Dallman2003}, proposed that chronic evaluation of gluocorticoids, such as cortisol may be implicated in the overconsumption of high fat and sugary foods and the propensity to store fat around the abdominal area. They argue that chronically elevated levels of glucocortical hormones increase  corticotropin-releasing factor activity in the central nucleus of the amygdala which increases stimulus salience and abdominal obesity. This mechanism then moderates metabolic inhibitory feedback on the catecholamines in the brain and the expression of corticotropin-releasing factor. Accordingly, the authors propose that, in an attempt to dampen activity in the brain,  the same mechanisms which mediates hyperactivity in insomnia facilitates overconsumption of high fat and sugary foods as well as promoting abdominal obesity. 
Population studies have also demonstrated a strong associated between OSA and chronic diseases including cardiovascular disease, hypertension, diabetes mellitus and stroke (Somer et al, 2008) \citep{Kato2009}. Moreover, as with insomnia, a strong relationship has also been shown between OSA and obesity and emerging evidence suggests a reciprocal interaction \citep{Passos2010}\citep{Malhotra2002}.  \citet{Ong2013} propose that obesity causes changes to the upper airway structure and function, causes 'reductions in resting load volume and negative effects on respiratory drive and load compensation' compensation' \citep{Hargens_2013}.  
Several studies \cite{Marshall_2002}\cite{Bryant_2004} have highlighted the reciprocal relationship between sleep and the immune system whereby sleep disturbances affect immune function \citep{Born1997} \citep{Everson1993} and activation of the immune system disturbs sleep patterns \citep{Sp_th_Schwalbe_1998}\citep{Takahashi1999}. Thus sleep disturbance may be linked directly to the pathogenesis of chronic inflammatory conditions such as asthma, rheumatoid arthritis and inflammatory bowel disease. For example, sleep disturbances are one of the major modifiers of asthma and can directly affect its course and severity. Specifically, sleep disturbances have been shown to negatively affect respiration, arousal responses and airway clearance \citep{D_Ambrosio_1998}. This effect is thought to be underpinned by prolonged supine posture, intrapulmonary pooling of blood, alterations in balance between the parasympathetic and sympathetic nervous system, sleep induced reduction in lung volumes \citep{Ballard_1999}
Another significant factor which may mediate the relationship between chronic conditions and sleep disorder is pain. It has been shown that chronic conditions associated with pain are associated with a higher prevalence of sleep disorders than conditions that are not \citep{Benca2004}. Although the relationship between pain and sleep remains unclear \citep{Drewes2019} \citep{Roehrs2017,Roehrs2005}, some have suggested that pain has an arousal-enhancing effect that prevents the initiation and/or maintenance of sleep. Others argue that pain and disturbed sleep are underpinned by common neurobiological pathways and that poor sleep negatively affects pain processing causing increased pain sensitivity \citep{Moldofsky_2001}\citep{Smith_2004} \citep{LAUTENBACHER_2006}. Again, there is evidence of a reciprocal interaction between sleep and pain with disturbed sleep increasing pain sensitivity  and with pain sensitivity decreasing following deep, less fragmented sleep \citep{Bigatti_2008}
In sum, the examples above illustrate how sleep disturbances may be implicated in the pathogenesis of a range of chronic conditions either by exerting their effects directly (e.g. via the immune system) or indirectly (eg. increase appetite leading to overeating of unhealthy food). Moreover, example also show how sleep disturbance can exacerbate the impact of chronic conditions (for example by increasing pain sensitivity). To further illustrate this point with cardiovascular diseases as an example, insomnia has been shown to reduce compliance with anti-hypertensive and other cardiovascular medications \citep{Haaramo_2013}. Moreover, the presence of insomnia also predicted the development of cardiovascular  conditions including cardiovascular disease including \citep{Sands-Lincoln2013} and myocardial infarction  \citep{Laugsand_2013}, independenlty of traditional risk factors (Spiegelhalder K, Scholtes C, Riemann D. The association between insomnia and cardiovascular diseases. Nature and science of sleep. 2010;2:71–78). Thus identifying and treating sleep disturbance has the potnetial to preven
This evidence points to importance of identification of sleep disturbances in people with chronic conditions and also suggests the important of treatment of either the sleep disorder its self or its moderating factors (e.g weight gain, pain). Next we explore the evidence such intervention in people with chronic conditions. 
Cognitive Behavioural Therapy has been shown to be an effective treatment for adults with insomina with clinically meaningful effect sizes \citep{Trauer_2015}  Music  therapy has proved effective for both acute and chronic sleep disorders (Wang, Sun, and Zang, 2014), with massage, acupuncture, natural sounds and music videos being reported to be effective in health care settings (Hellström and Willman, 2011).  As discussed above physical activity is often recommended for obesity. Given the reciprocal interaction between obesity and sleep physical activity has also been explored for the treatment of sleep disorders. Interestingly, in several cross sectional studies physical inactivity has been shown to be a risk factor for poor sleep and insomnia \citep{Chasens2012}\citep{Paparrigopoulos2010}\cite{Foley2004}\citep{Morgan2003}. With respect to insomnia, physical activity has been shown benefit people with sleep disorders but this was dependent but this was dependent on the type and intensity of the physical activity, with moderate-intensity aerobic exercise proving beneficial as opposed to high intensity aerobic and moderate-intensity resistance training  \citep{Passos2010}. A plethora of studies have also shown amelioration of OSA and associated symptoms such as excessive daytime sleepiness as a function of increased physical activity and/or diet \citep{Tuomilehto_2009}\citep{Tuomilehto_2013}\citep{Kuna2013}\citep{Foster2009}.
 
Conclusion - overall re health behaviours as they pertain to chronic conditions 
It is noted however, that simply providing information on modifications to health behaviours is not sufficient to elicit behaviour change. The use of behaviour change theory or behaviour change techniques is needed (Michie, Fixsen, Grimshaw, and Eccles, 2009), such as self-monitoring, goal setting, goal review and feedback; proving to increase the likelihood of behaviour change (Michie et al., 2009). Based on the upward spiral theory of lifestyle change, increasing positive affect will encourage adherence to a new behaviour change (Van, Rice, Catalino, and Fredrickson, 2018), mediated by increasing HRV and social connectedness (Kok and Fredrickson, 2010). There is a need to build positive psychological experiences in parallel with the ongoing medical treatment to both increase treatment adherence and improve health and wellbeing through other routes.
 
5.1.2: Positive Psychological Moments/experiences : 
Mental illnesses are no different from heart disease, diabetes or any other chronic illness. All chronic diseases have behavioral components as well as biological components. The only difference here is that the organ of interest is the brain instead of the heart or pancreas. But the same basic principles apply." (Thomas R. Insel, MD, director of the National Institute of Mental Health)
 
Our theoretical models outline mechanisms by which psychological experiences can, if positive, facilitate individual pathways to health and wellbeing and if negative, facilitate pathways to ill-health and premature mortality (Kemp, Arias, & Fisher, 2017a; Kemp, Koenig, & Thayer, 2017b). Our models provide extensive evidence that psychological experiences, alongside genetics, environmental influences and their interactions (epigenetic processes), play a critical role in the aetiology of mental and physical health conditions via a range of downstream allostatic processes (see Kemp et al, 2017 for a comprehensive review). In our updated GENIAL model we use the term ‘psychological experiences’ to refer to an individual’s interpretation of life events and the temporal narrative relating to the events over one’s life course via cognitive and emotional processes.
 
It is generally accepted that biology, the environment, adverse life events, personality and psychological attributions are all important in understanding the aetiology of mental health problems [Engel, 1977]. For example, genetical abnormalities have been implicated in the aetiology of mental health disorders (Sullivan, Neale, Kendle, 2000), coupled with the ‘additive’ effects of negative life events and environmental factors (Guze, 1989) which all negatively affect psychological functioning (Van Os, Kenis, Rutten, 2010). In terms of psychological experiences, much literature indicates that reasoning abilities, thinking styles and behaviour are critical in the aetiology and maintenance of mental health conditions (Kinderman, 2005). However, some authors have argued that psychological factors are the ‘symptoms’ of gene or gene-environment interactions (Guze, 1989; Pilgrim, 2002). On the other hand, it has been suggested that rather than being ‘symptoms’ disturbances in psychological processes caused by biological and social vulnerabilities and environment and life events are the final stage in a chain of events which may lead to mental health disorders (Kinderman, 2013). For example, in a large-scale eloquent study, including 32,827 participants, Kinderman et al. (2013) showed that psychological processes determined the ‘causal impact of biological, social and circumstantial risk factors on mental health’. Thus, psychological processes or ‘experiences’ (as term in our framework) far from being symptoms of gene-environment interactions may serve as the gateway to mental ill health or wellbeing This suggests that interventions at the level of ‘psychological processes’ (experiences) has great potential to reduce mental health difficulties, which in and of themselves are one of the leading causes of chronic disability (WHO, 2011) and costed an estimated $2,500 billion worldwide in 2010 (Boom, 2011).
 
In addition to psychological experiences being implicated in the causality of mental health conditions, we are beginning to understand the role that early psychological experiences may have in pathways to chronic physical ill-health. For example, Von Korff, Scott (2009) showed that >=3 childhood adversities were independently related to onset of diabetes in adulthood. The authors also showed that negative psychological experiences in childhood were associated with onset of asthma in a dose dependent way. More recently, \citet{Scott2016} S have shown that negative psychological experiences in childhood is strongly associated with adult onset heart disease. 
 
To recapitulate evidence suggests that psychological experiences can play a critical role in the causality of mental health and physical health disorders. Epidemiological studies have also shown that common mental disorders and physical disease are strongly inter-connected, highly co-morbid and share critical pathways to ill health and disease (O’Neil et al. 2015; Druss, Walker, 2011[zf2] ). For example, in a study of 245,404 participants from 60 countries across the world, an average of between 9.3-23% of participants with one or more chronic physical condition had co-morbid depression (Moussavi et al., 2007).  This is significantly higher than depression rates in people without a chronic physical disease (p>0.0001). Moreover, even after adjustment for health conditions and socioeconomic factors, depression had the largest effect on worsening mean health scores. The authors conclude that participants with one or more chronic condition and co-morbid depression had the poorest health of all of the disease states. 
 
Cardiovascular disease, type 2 diabetes mellitus, cancer and chronic respiratory diseases are often referred to as the ‘big four’ chronic conditions, because in combination, they account for more deaths than any other. However, if one considers the global burden of chronic conditions in terms of disability rather than mortality, major depression is the second leading cause of disability (O’neil, Jacka, Quirk, Cocker and Taylor and Berk, 2015) preceded only by cardiovascular disease. In terms of disability, ‘the big four’ only account for only (54%) of all related disability adjusted life years (DALYs). Although, relative to physical health conditions, mental disorders are associated with greater disability, they are much less likely to receive treatment and this holds true across the world (Von Korff MR, Scott KM, Gureje, 2009).
 
Prevalence rates for major depression are higher for people with physical illness relative to those without. For example, 29% for people with hypotension, 22% for people with myocardial infarction, 33% for people with cancer and 27% for people with diabetes (World Health Organization, 2003).[zf3]  The World Mental Health Survey showed odds ratios across countries for the relationship between heart disease and mental health conditions were; 2:1 for depression; 2:2 for anxiety; and 1.4 for alcohol dependence. The relationship between heart disease and mental health conditions (the two biggest contributors to the global economic burden of chronic disease) appears to be reciprocal. For example, major depression has been shown to increase the risk of the development of cardiovascular disease (Gasse, Laursen, Baune, 2014). For example, strong relationships have been reported between early onset common mental health disorders and heart disease in adulthood (Gasse, Laursen, Baune, 2014). Conversely, having a physical illness is one of the strongest predictors of depression (O’Neil et al. 2015; Wilhelm K, Mitchell P, Slade T, 2003). In their meta-analysis, Roest, Martens, DeJonge, Denollet (2010) revealed anxiety disorders also increase the risk for cardio-vascular disease and cardiac related death. The relationship between mental health conditions and chronic conditions remains strong across a plethora of chronic conditions. For instance, type 2 diabetes mellitus, has been shown to increase the risk for depression (Rotella and Mannucci, 2013), anxiety (Wandell, Ljunggren, Wahlström, Carlsson, 2014) as well as schizophrenia, bipolar disorder and post-traumatic stress disorder. Meta-analyses have also shown a strong relationship between diabetes and cognitive impairment (Vancampfort D, Correll CU, Galling B, et al, 2016). Respiratory diseases and cancer have been linked with depression (Caruso R, GiuliaNanni M, Riba MB, Sabato S, Grassi, 2017). In the World Mental Health Survey, mood, anxiety, and substance dependency were shown to preceded a diagnosis of asthma (Scott, Lim, Al-Hamzawi, 2015).
 
These common mood disorders appear to share an underlying diathesis whereby mechanisms that predispose individuals to depression and anxiety for example, contribute to the development of a range of chronic physical health conditions across the life span. A greater understanding of this common underpinning diathesis is needed to better develop preventive interventions and well as treatments. Our original GENIAl model lays the foundations from which these underpinning mechanisms can be better understood (Kemp et a al. 2017). What is clear, is that interventions that fail to appreciate the role the causal role of psychological experience in physical and mental health as well as the reciprocal relationship between physical and mental health miss substantial opportunities in the prevention and the amelioration of chronic conditions. Moreover, the biases in treatment towards physical illness in the health service is inefficient given that high degree of co-morbidity with mental health conditions because we know that mental ill health affects adherence to treatments and prognosis. DiMatteo, Leeper and Croghan (2000) showed that people with depression were three times less likely to adhere to treatment regimens that people without depression. This commissioning bias also ignores the evidence that health-related quality of life is significantly lower for depressed patients than for people with physical health conditions for example, asthma, arthritis, and diabetes [Moussavi S, Chatterji S, Verdes E, Tandon A, Patel V, et al. (2007)].
 
Given the role of negative psychological experiences in creating vulnerabilities to chronic conditions and mental health disorders it follows that interventions that target psychological experience have the potential to prevent or ameliorate the impact of the mental and/or physical health conditions.
 
 [zf2]Check this is an epidemiological study
 [zf3]World Health Organization, 2003.  Investing in Mental Health. Geneva: WHO}