When Happy Met Healthy

Adjacent possibility theory describes how small alterations can achieve great impact. It is argued that by mapping the current dispositional state of a population, and identifying patterns of behaviour that are adjacent but more desirable to the current, individuals can be directed to a more achievable alternative. This gradual approach to change is thought to be highly effective in facilitating stepped movement toward desirable behaviour, particularly for communities who have previously demonstrated fierce resistance to change.

Adjacent possibility theory presents a somewhat similar premise to that of ‘nudge’. Both nudge and adjacent possibility theory appreciate the importance of lowering effort demands and the power of small alterations. However, their respective nudges operate at different scales. Techniques such as choice architecture, a popular component of nudge practice, target behaviour at the time of its occurrence and attempt to alter the context in which behaviour takes place. Alternatively, the dispositional nudging of adjacent possibility theory considers the idea of gradual change at an earlier stage in the intervention process, by identifying the very behaviours that may be desirable and possible to change. The fundamental premise of both theories is that small changes are effective, obtainable and sustainable. Whilst some controversy remains over the efficacy of nudge techniques, the idea of making the initiation and maintenance of behavioural change more possible and comprehensible for our target populations clearly aligns with evidence-based core principles of behavioural science.

The ideas presented by adjacent possibility theory hold significant promise for investigation within the healthcare industry. A growing body of evidence suggests that positive psychology wellbeing interventions (PPWBIs) may be effective in decreasing the prevalence of health-risk behaviours such as sedentary behaviour, poor diet and tobacco and alcohol harm. Therefore, it is pertinent to examine the potential of enhancing psychological wellbeing as a suitable adjacent possibility for populations at risk of non-communicable diseases (NCDs). Recent years have witnessed a rapid increase in the number of highly effective and light-resource interventions targeted to improving psychological wellbeing, making this a highly attractive option on a practical level. However, examining healthy behaviour through the lens of psychological wellbeing also suggests an encouraging method for understanding and tackling the cross-sectional themes underlying the clustering of NCDs.

Historically, psychological investigation has operated within the confines of the illness ideology, focusing upon pathological factors which precipitate and maintain disease. Alternatively, positive psychology emphasises the value of fostering traits which buffer individuals against disease, contribute to resilience and facilitate optimal functioning. Devoting attention to this opposite end of the spectrum is highly promising for gaining novel understanding in a relatively unexamined area.

There is an established and well recognised relationship between psychological health and physical health, however this link has been almost exclusively described in terms of the physiological effects of stress. Most commonly investigated in the context of cardiovascular disease, a multitude of evidence suggests that the harmful effects of chronic cortisol levels in enhancing the risk of athersclerosis as a result of prolonged exposure to high-stress environments. Consequentially, it is thought that reducing exposure to stress, or developing effective coping strategies can reduce the likelihood of experiencing conditions such as cardiovascular disease. However, could the relationship between psychological wellbeing and health extend beyond the physiological mechanics of stress?

An alternative explanation to the co-occurrence of positive wellbeing and decreased CVD risk is that happier individuals are more likely to engage in healthy behaviours relevant to CVD prevention, such as physical exercise, healthy diet, and moderate drinking. Whilst evidence shows that psychological wellbeing is often a consequence of healthy behaviour, if a bi-directional relationship exists between psychological and physical health, enhancing wellbeing could be an essential and novel route for healthy behaviour intervention.

Systematic investigation certainly suggests that a behavioural pathway may at least partially explain the link between psychological wellbeing and CVD. For example, numerous cross-sectional studies have indicated that individuals with greater psychological well-being are more likely to be physically active, a finding which has been replicated for individuals with the greatest life satisfaction and optimism. In addition, individuals with higher ratings of optimism were found to eat fewer sweets and greater amounts of fruit and vegetables than their less optimistic counterparts. Lastly, in a study investigating the clustering of lifestyle behaviours and their relationship with CVD and psychological health, participants who engaged in four to five healthy behaviours were 4.7 times more likely to experience optimal wellbeing than those engaging in zero or one.

Although the cross-sectional nature of this research makes it hard to determine the direction of the relationship between psychological wellbeing and healthy behaviour, it is additionally supported by prospective studies. For example, the most optimistic individuals in a baseline sample, were found to be 30% less likely to develop CVD or suffer a heart-disease related mortality than the least optimistic over the next 8 years. Again, the possibility of a wellbeing-related behavioural component may explain findings of this nature, given the results of several longitudinal studies. For example, increases in positive affect over a five year period were found to co-occur with improvements in physical activity, sleep quality and medication adherence. Baseline positive affect was also associated with desirable health behaviours such as physical activity, sleep quality, medication adherence and smoking, however baseline positive affect did not predict positive affect at follow-up, suggesting the importance of efforts to sustain and enhance psychological well-being over time. Additionally, participants with greater optimism ratings were more likely to eat greater amounts of fruit and vegetables at baseline as well as demonstrating a slower decline in the healthiness of their eating habits across adolescence, relative to less optimistic peers. Furthermore, over the course of a 10 year study, high emotional vitality was found to significantly relate to a reduced risk of hypertension whilst controlling for age and demographic variables. This relationship was found to be partially explained by favourable health behaviours, however in contrast to previous research, no significant effect of optimism was found. Evidence has also implicated the role of psychological wellbeing in smoking; less optimistic adults were significantly more likely to become smokers one year later.

The relationship between psychological wellbeing and healthy behaviour has been investigated to some extent via laboratory studies which experimentally induce psychological wellbeing and subsequently measure food choice and consumption. Whilst one set of studies evidenced a significantly positive relationship between positive mood and reduced food consumption, this findings from this area are as yet inconclusive, with some studies demonstrating a lack of any effect of positive mood on food consumption, or even an increased effect. Similar controversy exists over reported cravings of smokers in varying affective states.

Despite the relatively light investigation conducted so far in this domain, the conclusions of the outlined studies present an encouraging argument for the efficacy of PPWBIs in aiding the initiation and maintenance of healthy behaviours, which are known to have a highly significant role in preventing NCDs. Whilst the vast majority of research already conducted has been undertaken with clinical populations, the use of PPWBIs may be particularly pertinent for individuals who engage in health risk behaviours, however have yet to experience the saliency of their adverse effects. Importantly, PPWBIs such as gratitude journaling have demonstrated a prolonged increase in neurological sensitivity in the pregenual anterior cingulate cortex, which is involved in both sensation of reward and action-outcome prediction. The propensity to increasingly devalue rewards the more they are chronologically distanced from an individual, known as  temporal discounting, has been evidenced as a distinct problem in the maintenance of healthy behaviour such as resisting alcohol or unhealthy food. Activities which enhance a persons ability to self-regulate over time may provide a highly effective method of limiting the tendency to temporally discount, especially if such activities can be replaced with inherently rewarding tasks. This evidence demonstrates that PPWBIs may serve this function, however additional research is needed. However, the suggestion of a bi-directional relationship between PPWBIs and healthy behaviour certainly holds relevance for the stepped change and positive spiralling advocated by adjacent possibility theory.

Consequentially, the mission to reduce the prevalence of NCDs could substantially benefit from further investigation into the relationship between psychological wellbeing and healthy behaviours, but also the mechanisms which could explain how such a relationship operates. Further attention should be devoted to wellbeing constructs which may antecede healthy behaviour, such as enhanced motivation, persistence, challenge-seeking and navigation of the chasm between short and long-term behavioural consequences.