Brains, bodies and social hierarchies

BY KEELY A. MUSCATELL, Ph.D. ILLUSTRATION BY WILLIAM HOGAN

Socioeconomic status (SES)— or one’s annual income, years of education completed, and occupation—has long been appreciated as a critical determinant of longevity. Indeed, there are large gaps in life expectancy for those at the top of the socioeconomic ladder compared to those at the bottom, and at many points in between But how can a “macro-level” societal factor, like how much money you make or if you graduated from college or not, “get into the skull and under the skin” to influence an individual’s health and well-being?

Psychologists, sociologists, public health researchers, and, more recently, neuroscientists, are all interested in understanding socioeconomic influences on the brain and body. It perhaps comes as no surprise that living in poverty, without enough money to meet basic needs like food, water, and shelter, or to go to the doctor when you’re sick, can take a toll on health

But, interestingly, the data show that the relationship between socioeconomic status and health is present even in countries with universal health care, suggesting that there is more to the psychological experience of being lower in SES beyond just access to health care. Further, some intriguing research shows that our subjective perceptions of our standing in the US are a better predictor of health compared to more objective indicators like income and education. Together, data like these have led some to conclude that, in addition to our objective life circumstances, how we perceive our social standing and how we compare to others in our environments can impact our health

Given the robust associations between socioeconomic status and health, more recent research has focused on understanding the mechanisms, or pathways, through which SES may impact disease processes and health outcomes. Some of this work has utilized advancements in brain imaging technology to explore how SES impacts the functioning of the brain in ways that could lead to poor health outcomes. Other work has focused on the relationship between socioeconomic factors and physiological processes, such as the functioning of the cardiovascular system and the immune system. What follows is an overview of these areas of recent research, all of which are attempting to fill in pieces of the complex puzzle of the relationship between SES and health

Psychologists, sociologists, public health researchers, and, more recently, neuroscientists, are all interested in understanding socioeconomic influences on the brain and body.

SES Impacts Health-Relevant Brain Functioning

Much past research on the effects of SES on the brain has focused on how socioeconomic factors influence the development of brain regions important for academic achievement among children and adolescents. Together, this work suggests that children whose parents’ make less money or have fewer years of education have different trajectories of development in brain structure (i e , the size and shape of different brain regions) and in brain function (i e , what brain regions are used to perform a task) that may prevent them from performing to their full potential in school and beyond. This research has been critically important in facilitating our understanding of how SES in early life can shape brain development in ways that may perpetuate economic inequality. But given that most SES-based health disparities don’t develop until much later in life, when adults start to develop chronic diseases like heart disease and diabetes, more recent work has begun to shed light on how SES influences neural activity in brain regions that may contribute to chronic disease development among adults.

One brain region that has received a lot of attention for its potential role in contributing to SES-based health disparities is the amygdala. The amygdala is an “infamous” brain region that is often incorrectly characterized as a “fear center” of the brain. Instead, our current understanding of the primary function of the amygdala is that it plays an important role in helping detect salient information in the environment (which could be feared things, like snakes or spiders or angry faces, or could be positive things, like a smiling baby or winning a raffle). The amygdala is important for health because it has strong connections with other brain regions that can start physiological cascades like the “fight or flight” response, which, if chronically activated, can take a toll on the body and put individuals at risk for chronic disease development.

Given the amygdala’s importance for health, a number of prior studies have investigated the association between socioeconomic factors and amygdala responses to stressful or threatening stimuli, like angry faces or receiving negative performance feedback. This growing area of work shows that individuals from lower SES backgrounds have greater amygdala activity to stressful, threatening stimuli, compared to higher SES individuals. Although speculative, this suggests the possibility that lower SES individuals are more reactive to stressors, which, over time, could increase risk for poor health outcomes.

But of course, it’s not only our initial, “knee jerk” response to a threatening situation that is important for health over time, but also how we cope with the situation. Psychological scientists often refer to this process as “emotion regulation,” or our ability to turn off our negative emotional responses with different coping strategies. The ability to successfully turn down emotions is facilitated by activity in prefrontal regions of the brain, which, via their connections to other regions like the amygdala, can help down-regulate our initial emotional responses. To date, only two known studies have asked if SES influences neural responses during emotion regulation. Both of these studies found that people from lower SES backgrounds showed lower levels of activity in the prefrontal cortex when they attempted to regulate their emotional responses to negative images, like a picture of a gruesome car crash. Interestingly, one of these studies found that higher levels of chronic stress among people from lower SES backgrounds was a major contributor to this association between SES and lower prefrontal cortex activity, once again pointing to stress as a critical pathway through which SES may influence the brain and, ultimately, health.

It’s important to pause here and point out that studying associations between SES and brain function raises challenging physiological questions. For example, do people from lower SES environments have brains that are “wired differently” based on something inherent in them (like genetics), or are factors related to the socioeconomic climate the drivers of observed differences in brain functioning between the rich and the poor? In other words, if there are differences in brain functioning between people who have less and those who have more, is that due to “nature” or “nurture”?

Interestingly, research suggests that people with less money or fewer years of education are not inherently less capable than those with more, but rather that the psychological toll of being low income can impact the way the brain functions. For example, research by Sendhil Mullainathan and Eldar Shafir, discussed in their book, Scarcity: Why Having Too Little Means So Much, has shown that cognitive performance varies with current financial resources, even within the same person. In a fascinating study on farmers in India, researchers found that immediately following harvest time, when the farmers were comparatively rich, they performed well on challenging tasks designed to test their executive functioning, specifically their ability to plan, maintain, and manipulate information (analogous to “thinking on your feet”). Before the harvest, when the farmers had fewer financial resources, they performed worse These findings suggest that cognitive ability is not simply a trait that operates at the same level regardless of circumstances, but rather that our financial situation at any given time can influence how well we perform. In other words, it’s unlikely that people with fewer years of education or who make less money are inherently less capable than those with more, but rather, that the stress of not having enough financial resources and needing to constantly juggle what little money we have can take a toll on our cognitive performance.

It’s not difficult to imagine the implications this has for work productivity and school performance; for people living paycheck to paycheck or reliant on student loans, their work or academic performance may suffer during times of the month or year in which they have less money, because the lack of resources is preventing them from functioning at their peak

Taking Social Class to (the) Heart

It is now clear from the past decade of neuroimaging research that one’s socioeconomic status influences how the brain is functioning, particularly activity in the amygdala and the prefrontal cortex, both of which are critical for how we react to and recover from stress. But how does that brain activity translate into physiological changes that can influence health? Nowhere is the influence of SES on the body clearer than in the cardiovascular system. Hundreds of studies have shown that individuals from lower SES backgrounds have higher blood pressure and greater arterial plaque buildup, and ultimately suffer heart attack and stroke at higher rates, than those of higher status.

Unhealthy behaviors undoubtedly contribute to this link: tobacco companies are more likely to advertise in and offer discounts at shops in low SES neighborhoods, contributing to greater cigarette smoking; many lower SES communities are “food deserts,” with an abundance of fast food restaurants and convenience stores and a lack of healthy, affordable food options (like grocery stores and farmers markets); and lower SES neighborhoods are less likely to have parks and other green spaces where people can safely exercise and spend time outdoors. Over time, these limited opportunities for healthy eating, physical activity, and smoke-free living can take a toll on the heart and arteries, increasing risk for heart disease and major cardiovascular events like stroke and heart attack.

Beyond these behavioral pathways linking SES and cardiovascular risk, research suggests that cardiovascular responses to stress represent another way in which social hierarchies can impact the heart. So many studies have investigated this question that a meta-analysis, or “study of studies,” was recently conducted to determine the strength of the relationship between SES and stress reactivity across the whole body of research in this area

This seminal paper reported a somewhat surprising pattern of findings. There were no differences in blood pressure or heart rate responses during stressful experiences as a function of SES There were, however, differences in how the heart was functioning once the stressor was over, with heart rate and blood pressure remaining elevated for longer in lower SES individuals. This suggests that everyone, regardless of SES background, has an initial cardiovascular response to a stressor, but that lower SES individuals recover more slowly. In other words, stress may “live on” in the bodies of people with lower social status, producing greater wear and tear on the heart and arteries that leads to greater health risks over time This may be due in part to the lower levels of prefrontal cortex activity in the brain during emotion regulation mentioned above, though no known research has tested this directly.

Promoting Health Equity Moving Forward

If you’re like me, it’s distressing to think that something as uncontrollable as the social class you’re born into determines your lifespan. So what can we do to mitigate the deleterious impacts of socioeconomic status on the brain and body? Some ongoing research is testing whether simply giving money to people living in poverty can change their cognitive and emotional functioning, while work by Natalie Brito at New York University examines if paid parental leave policies could lessen the financial burden of parenthood, which would benefit everyone, especially those with lower SES

Such institutional changes at the level of societal structure may prove useful for promoting health but would require significant policy change that not all Americans favor This awareness has led some psychologists to ask if there are other strategies we can arm lower SES families with to promote better health outcomes even in the absence of sweeping policy change

One interesting intervention—called Parents and Children Making Connections- Focusing on Attention worked with parents of young children to provide them with strategies for dealing with regulating emotional responses to stressors in the family, and for training their children’s’ attention After eight weeks of attending two-hour small group classes, children whose parents were in the intervention showed significant improvements in cognitive function and in brain activity critical for attention, compared to those in a control condition whose parents did not receive the intervention. This suggests that working with parents to help develop emotion regulation strategies and strengthening childrens’ abilities to sustain their attention on a task could facilitate better outcomes. Of course, there are challenges with interventions like this, given the time commitment involved (i.e., eight weeks of two-hour classes) and the fact that lower SES parents may not have the time available or mental bandwidth to dedicate to such training programs due to working multiple jobs, etc.

Further, the research showing that it’s not just objective economic circumstances that matter for health, but also our perception of our standing in a social hierarchy, suggest that we may also want to implement interventions to improve health for people who feel low on the social ladder So, what else can be done? To the extent that individuals who perceive themselves to be lower on the social ladder feel that they are not valued and don’t belong in certain places, it becomes much harder to shut down the stress response.

Groundbreaking research by Gregory Walton and Geoffrey Cohen at Stanford University suggests that this is indeed the case When lower SES minority students at Stanford were given a brief social belonging intervention emphasizing that they, and people like them, did belong and could thrive at such a prestigious university, their grades, and their health, improved drastically, even when measured four years later. So, while we should strive to ensure that everyone’s material needs are met, we should also be keenly aware that social belongingness is another life-sustaining need that all must have to live happy, healthy lives. To achieve true health equity then we need to promote both monetary and psychological fulfillment so all Americans can thrive, regardless of their social class background l

Financial Disclosure: The author has no conflicts of interest to report.

BY BRENDA PATOINE

ILLUSTRATION BY LIA KANTROWITZ