Health neuroscience 2.0: integration with social, cognitive and affective neuroscience

Health is a primary concern, whether it is our own health or the health of friends and family. This is never more apparent than when threatened. The current pandemic provides a sad reminder of just how vulnerable our health can be. Researchers share this concern. Even the founders of modern psychology, including William James and Willhelm Wundt, were originally trained in medicine and had interests in health before turning to Psychology. Understanding health is, therefore, interconnected with the goals of Psychology. Yet health, defined nearly 75 years ago by the World Health Organization (1948) as a complete state of physical, mental and social well-being and not merely the absence of disease or infirmity, continues to be an elusive and, sometimes, poorly understood phenomenon. Health Neuroscience, articulated as its own field in 2014 (Erickson et al., 2014), is defined by its explicit focus on understanding how the brain affects and is affected by physical health. In this way, health neuroscience emphasizes the reciprocal ‘cross-talk’ between the brain and other aspects of the individual—the rest of the body (e.g. Garfinkel et al., 2014; Kraynak et al., 2019), the health behaviors and decisions we engage in (e.g. Erickson et al., 2011; Falk et al., 2011; Berkman, 2018), the people and society with whom we interact (Eisenberger and Cole, 2012), the environment within which we live (e.g. Calderon-Garciduenas et al., 2002). From these foci come three overarching goals: to understand the brain (i) as a predictor of health, (ii) as a mechanism linking social and affective experience with health and (iii) as a health outcome in and of itself. This Commentary briefly reviews where health neuroscience comes from and why it was formed, what the field looks like today and recommendations for what health neuroscience could look like tomorrow. Special emphasis is placed on how readers of Social Cognitive and Affective Neuroscience (SCAN) can contribute to the field. Well before the invention of modern brain imaging techniques, there has been a deep appreciation for the brain’s inseparable connection to aspects of physiology, psychology and behavior that contribute to health (e.g. James, 1890). Health neuroscience, however, represents the intersection of more contemporary research traditions: cognitive and affective neuroscience, health psychology, behavioral medicine, epidemiology and public health. From neuroscience, health neuroscience borrows perspectives that integrate peripheral physiological responding into their understanding of the function and structure of the brain. From health psychology, health neuroscience builds on the biopsychosocial approach to health—an approach in which biological responding, psychological processes and the social environment share equal footing and interact in meaningful ways to influence health. Behavioral medicine and epidemiology bring an emphasis on mechanistic mediators, treatment targets and predictors of health and its determinants at a large scale (e.g. globally, across a country or a neighborhood). And from public health, health neuroscience borrows emphases on preventative health behavior and an understanding of individuals as existing within a community, healthcare and health policy systems. Closely allied fields, such as population neuroscience and translational neuroscience, share similar origins (Falk et al., 2013; Woo et al., 2017; Berkman, 2018). Despite Paul Maclean’s early model of the brain—namely, the ‘limbic system’—as a substrate by which affective processes relate to chronic illness (MacLean, 1949), inclusion of the brain was either absent from or implicit in later influential models of human health (e.g. Ajzen, 1985; Rosenstock et al., 1988; Miller et al., 2009; Del Giudice et al., 2011). Regardless of the reasons, its conceptual absence lead to far-reaching consequences for health research in the psychological and behavioral sciences. If the intent of a theoretical model is to guide research by generating testable hypotheses one is, of course, more likely to test a hypothesis about predictors, processes or outcomes that are in a model than those that are not in the model. Exclusion of the brain, therefore, might have led to the conclusion that the role of the brain in health is ignorable. The biopsychosocial approach to health, as one overarching example, became popular because of its goal to understand how psychological factors ‘get under the skin’ to influence physical health. Though still a popular term, the idea that psychology ‘gets under the skin’ suggests that psychological experience somehow sneaks into the body. In reality, psychological experience walks straight through the front door—the brain. The exclusion of the brain, however, deemphasizes this fact and the brain’s role in health. Without conceptual inclusion and integration of the brain, sophisticated hypotheses about the brain’s role in health, particularly physical health, have been lacking. Indeed, conceptual inclusion of the brain in health necessitates a nuanced understanding of the brain that is more than an empty placeholder that sends predictive signals and receives inputs from the periphery. A related consequence is that conceptual integration of the brain with the rest of the body and broader context (e.g. one’s culture, environment, psychological experience) is still poor—a fact that stands against the desire to have a holistic understanding of health. In other words, exclusion of the brain leaves a fully articulated pathway by which psychological experience affects the body or how the body affects psychological experience, behavior and decision-making incomplete. Ignoring the brain at the theoretical level, therefore, trickles down to research implementation and moves understanding of the brain’s role in physical health, in particular, behind that of mental health. A broader consequence of excluding the brain is that the rigorous training needed to measure brain structure and function and link brain measures with other levels of analysis (e.g. branches of the autonomic nervous system) is also rare. Formal training programs outside of individual labs that emphasize both psychology and physical health, for example, exist in only a handful of institutions and remain rare at the departmental and institution levels. This fact might appear surprising given the numerous resources dedicated to health worldwide (private and public funding, research societies, journals and textbooks). Together, the exclusion of the brain in theoretical models of health and dearth of formal training are particularly detrimental for discovery with brain measurement methods—which require a high level of expertise and substantial financial burden to conduct. Stepping away from the research itself, real change to individual, community and population health requires the attention of policy-makers. Research has shown that information is perceived to be more believable and credible when it is seemingly based on neuroscience and incorporates measures of the brain (McCabe and Castel, 2008; Weisberg et al., 2008; cf Farah and Hook, 2013). The onus is, therefore, on the research community to demonstrate physical connections between the brain and health and then to manage this messaging once it reaches the level of policy. As an example relevant to all readers of SCAN, fMRI and EEG studies can be utilized to enhance the credibility of claims that social and affective experience bidirectionally influence physiology. Such connections are enormously meaningful for health. Brain research also produces new knowledge that complements other evidence on social and public health problems A clear example is the pervasive impact of socioeconomic disadvantage on the brain across the lifespan (McEwen and Gianaros, 2010; Farah, 2018). Such knowledge adds to what is already known about the patterning of chronic health problems at the forefront of policymaker’s minds (e.g. hypertension, type II diabetes, cancer and now coronavirus disease of 2019 [COVID-19]). Brain research helps us understand how these socially patterned health problems might be taking an added toll on the brain to confer risk for preventable adverse outcomes that are amendable to policy change. Since health neuroscience first took formal shape, a number of important steps have been made. We have defined a research space in which the brain and physical health share bidirectional influence and the three goals—to understand the brain as a predictor, mechanism and outcome—have been articulated. The following starts the journey toward Health Neuroscience 2.0 by revisiting the original three goals of health neuroscience. There is a long tradition within health psychology and medicine to use biomarkers to predict health in order to reveal points of intervention, intermediate outcomes and risk stratifiers. Such a tradition dovetails with an increasingly appreciated, if not yet widely accepted, perspective of the brain as a predictive organ (Berkman and Falk, 2013; Barrett, 2017; Woo et al., 2017; Gianaros and Jennings, 2018). The switch from previous understanding of the brain as solely reactive to predictive represents a paradigm shift in neuroscience and one that lends itself to one of the major goals of health neuroscience: using the brain to predict health and prevent disease. Illustrative examples from the current special issue that capitalize on this perspective include those that use state-of-the-science analytical approaches (e.g. machine learning to identify multivariate patterns of neural activity) to predict a host of the most pressing health issues facing society today: cardiovascular disease (Gianaros et al., 2020), obesity (Stice et al., 2019; Cosme et al., 2020; Donofry et al., 2020; Verstynen et al., 2020) and physical pain (Reddan et al., 2020). Similar approaches help us understand links between brain patterns of activity to emotional content and systemic inflammation, a key biological mediator linking psychological experience and health (Alvarez et al., 2020), or to health messages and population-level sharing of the information (Dore et al., in press). And supplementing the use of task-based imaging, there is also promise in examining links between resting state brain connectivity and health-relevant outcomes (Inagaki and Meyer, 2019; Mehta et al., 2019). Prediction of health outcomes from neural activity, however, has also proven difficult (e.g. Gianaros et al., 2020; Cosme et al., 2020), providing room for a number of future directions. At the most fundamental level, what health-relevant physiological responses are best predicted by brain activity? And, what boundary conditions (e.g. when and for whom) exist for reliable prediction? Moving toward a within-person, lifespan perspective on prediction, does the brain’s response to socio-emotional experience predict response to treatment, willingness to engage in preventative health behavior, or the progression of chronic disease within a person? At the broadest level, will the brain as predictor approach help us extend healthy years and slow the time in which disease negatively impacts function? Decades of research from epidemiology and public health have established that social and affective experiences are key physical health determinants. As examples relevant to all readers of SCAN, objective social indicators like social network size and subjective indicators like feelings of loneliness are robust predictors of health and mortality (Cacioppo and Hawkley, 2003; Christakis and Fowler, 2007; Holt-Lunstad et al., 2010). Yet, we know surprisingly little about the neurocognitive processes linking social indicators with health. Social neuroscience, in particular, is well positioned to unpack these relationships in terms of brain mechanisms. In the current special issue on health neuroscience, the brain is examined as a mechanism linking psychological stress and inflammation in cancer patients (Leschak et al., 2020) and early-life trauma, inflammation and symptoms of PTSD and depression in African American women (Mehta et al., 2019). Others assess basic mechanisms in healthy samples (a prevention oriented approach)—the brain’s response to painful or emotionally salient content as a mechanism underlying self-affirmation (Dutcher et al., 2020), support-giving (Inagaki and Meyer, 2019) and supportive touch’s effect on health (Reddan et al., 2020). Finally, Poulton and Hester, 2019 review brain mechanisms contributing to risky decision making and the development of substance use disorder. A noticeable missing piece in the goal to understand the brain as a mechanism is that, for the most part, mechanism is implied, but not tested or manipulated. For instance, resting state connectivity between brain regions and task-based activation in the dorsal anterior cingulate, anterior insula and amygdala in response to people in need are negatively related, suggesting that social experience might contribute to health by altering activity in these regions (Inagaki and Meyer, 2019). Mediation, however, was not directly shown. Future research could remedy this issue by directly testing mediation using the statistical techniques and experimental methods common to psychologists (e.g. as shown in Muscatell et al., 2016). For example, one could directly assess whether the neural processes widely studied in social neuroscience (prejudice, social influence, the self, social comparison, social norms, obedience and conformity, self-regulation, aggression, close relationships, etc.) mediate associations between stress (Cohen et al., 2016), social status (Matthews and Gallo, 2011; Cundiff et al., 2020) or social ties and health (Holt-Lunstad et al., 2010). Current understanding of the brain as a health outcome comes largely from the area of population neuroscience. Research in this area has identified differential brain patterns depending on socio-economic status, social network size and neighborhood (Falk et al., 2013; Gianaros et al., 2017). Additional emphases are on the negative effects of hypertension, metabolic syndrome, diabetes and poor sleep on the brain. Social, cognitive and affective factors remain important in all of these areas, but are wide open for additional research. As highlighted in Cardenas et al., 2019, one area ripe for further research is how pregnancy affects the structure and function of the brain itself. Other examples include whether repeated experiences of social rejection and peer victimization early in life alter the brain in ways that confer risk for suicide or self-harm later in life (Olié et al., 2017). These, and the questions posed above, are all critical questions to be addressed in future health neuroscience research. With the health by the pandemic and the reminder of health in the now is a pressing time to about physical health. 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