Internalizing Social Determinants of Health: The Ecosocial and Weathering Theories

An Introduction to Social Epidemiology

Healthy People 2030 emphasizes the need to focus on the social determinants of health (SDH), specifically with the goal to “create social, physical, and economic environments that promote attaining the full potential for health and well-being for all.” Social determinants of health refer to the nonmedical conditions and environments where people live, work, and play that ultimately impacts their health outcomes. The study of sociostructural factors on the distribution of health and disease is called social epidemiology. Although research evaluating the impact of SDH on health outcomes has only recently expanded, the notion that social conditions influence health originated at the beginning of the 19th century. Villerme, Virchow, and Chadwick all examined the relationship between poor socioenvironmental conditions and disease. However, the advent of the germ theory, in which germs were considered the major cause of disease, overshadowed the impact of social conditions until social epidemiology resurfaced in the 1980s.

Since then, several models and theories have emerged to help explain the pathophysiology behind different population health distributions and health inequities. The germ theory introduced the dominant theory behind disease development—biomedical individualism, whereby (1) disease is fully attributable to individual-level biology, exposures, behaviors and, as such, is amenable to interventions through the healthcare system, (2) sociodemographic and contextual variables are considered secondary to biological causes of disease, and (3) populations and their diseases reflect the sum of individual-level phenomena. ^, Differences in disease distribution by race, ethnicity, and gender are attributed to innate genetics, biology, and cultural preferences. The “web of causation” was then introduced to challenge the concept of single “agents” causing disease and, instead, emphasize the complexity and intersections of risk factors that ultimately lead to disease. Additionally, the host–agent–environment epidemiological model became commonplace, describing the necessity for an external agent (e.g., infectious pathogen), susceptible host (e.g., human), and environment (e.g., extrinsic factors providing the opportunity for exposure) to produce disease.

Alternative theories, such as the psychosocial theory, propose that disease occurs due to mutual stressful interactions between social, individual, and biological factors in multilevel, interactive environments. The stress induced from these factors is then suggested to alter neuroendocrine function, leaving certain populations more susceptible to both physical and psychiatric diseases. More modern concepts, such as allostatic load (AL), stem from the psychosocial theory. Allostatic load relies on the fundamental concept of allostasis, where body systems achieve homeostasis after exposure to stressors. Allostatic load, on the other hand, refers to the physiologic “wear and tear” induced from chronic overstimulation of the hypothalamic–pituitary–adrenal (HPA) axis and sympathetic–adrenal–medullary (SAM) pathway, leading to dysfunctional cardiovascular, metabolic, and immune systems. Social capital and cohesion are proposed as the most promising interventions for decreasing risk of disease according to the psychosocial theory.

Another theoretical framework focuses on upstream–downstream effects, also known as “the political economy of health” or the “social production of disease,” where economic and political determinants serve as structural barriers to people living healthy lives. Specifically, society's priorities of capital accumulation lead to economic and political decisions that create, enforce, and perpetuate economic and social privilege and inequity, which is considered the fundamental cause of health inequities. Recognizing nonbehavioral causes of health issues arose in response to criticisms of the dominant “blame-the-victim” “lifestyle” theories that persistently emphasized individuals' responsibilities in “choosing healthy lifestyles” without considering alternative factors contributing to health outcomes. ^, Interventions call for redistributive policies that reduce poverty and income inequality, termed “healthy public policies,” as well as community empowerment for social change. However, this upstream framework primarily describes how social factors either accelerate or hinder “normal” biological processes, only superficially discussing the interaction between social and biological factors.

Ecosocial Theory

As such, Nancy Krieger developed the ecosocial theory in 1994 to incorporate multiple existing theories. Specifically, the ecosocial theory is composed of four key elements: embodiment, pathways of embodiment, the cumulative interplay of exposure, susceptibility, resistance, and agency and accountability, which are further described in Table 2.1 . ^, The ecosocial theory considers biology and society as an “intertwining ensemble” in which individuals are situated within social groups whose everyday lives are shaped by the dominant society's economic and political priorities, which aim to benefit those individuals claiming superiority, ultimately leading to oppression and discrimination. ^, These discriminatory effects impact individuals' physical and social environments (i.e., pathways of embodiment), which are ultimately internalized (i.e., embodiment) from the cellular level throughout the individual and household within their lifetime. ^, Krieger, however, also emphasizes the need to consider the historical context of all levels (i.e., individual, intergenerational, societal, ecological), which will influence individuals' initial susceptibility and subsequent response to the oppression (i.e., cumulative interplay of exposure, susceptibility, resistance) ( Fig. 2.1 ). ^, Nevertheless, the ecosocial theory posits that society's social system and the states that employ these priorities are responsible (i.e., agency and accountability) for generating the inequitable living and working conditions that have led to the current distribution of disease. ^,

Krieger's ecosocial theory challenges biomedical individualism and the construct that health outcomes are simply “natural” or “individually innate.” Rather, concepts such as race are social constructs created to racialize biology, demarcate groups, and generate inequities that are a consequence or expression of racism. Inequitable social conditions are not “natural” but constructed from people who had a purpose (and are thereby accountable) in mind. Krieger situates health behaviors in their social context, arguing that the health effects pathologically induced from the collective phenomena of discrimination and oppression cannot be reduced to individual attributes. Patterns of disease represent the biological consequences (from gene expression to physiological changes to behavioral development) of living and working conditions that are assigned from society's economic and political priorities. The ecosocial theory therefore not only addresses what drives social inequities in health but also who creates these injustices. As such, Krieger emphasizes that research on interventions should focus not just on the healthcare system, public health departments, and individuals, but also the broader determinants of health through widespread social action.

Discrimination: An Embodiment Pathway

Krieger proposes that oppression is expressed through multiple “pathways of embodiment.” Namely, discrimination leads to economic and social deprivation, the creation of exogenous hazards (e.g., toxic substances, pathogens, hazardous conditions), social trauma (discrimination, mental/physical/sexual trauma), targeted marketing of harmful commodities (e.g., tobacco, illicit drugs), inadequate or degrading healthcare, and ecosystem degradation (e.g., exiling indigenous populations from their native land). To study the impact of oppression on health, however, three approaches have been recommended: (1) indirectly through inference, (2) directly through self-reported measures, and (3) through institutional/population-based measures. Indirect approaches involve adjusting studies for confounders and socioeconomic position, yet still seeing discrepancies in health outcomes among social groups. While this persistent difference may be due to inadequate socioeconomic measurements or unmeasured confounders, the remaining difference may also reflect unmeasured noneconomic aspects of discrimination.

Direct approaches use measurement instruments to inquire explicitly about patients' self-reported experiences with discrimination. ^, In 1999, Krieger reported on 20 studies in the public health literature that measured self-reported discrimination, three-fourths of which focused on race, three on gender, three on sexual orientation, and one on disability. Williams et al. published an updated review in 2003 evaluating 53 population-based studies examining the association between racial discrimination and health indicators. Multiple studies have noted positive associations between racial discrimination and psychological distress, major depression, anxiety, early substance use, psychosis, and anger. Similarly, studies demonstrated positive associations with poorer self-perceived health status, blood pressure, cardiovascular outcomes, cigarette smoking, and alcohol use. Since then, multiple reviews and metaanalyses have reported consistent associations between self-reported racial discrimination and poorer mental health with weaker relationships to poorer physical health.

A variety of instruments have been developed to assess exposure to self-perceived racism, such as the Schedule of Racist Events, Racism and Life Experience Scales, Experiences of Discrimination, Perceived Racism Scale, Everyday Discrimination Scale, Perceived Ethnic Discrimination Questionnaire, Multidimensional Inventory of Black Identity, and the Nadanolitization scale. However, these individual-level measures are limited by survey design and participant recall bias, which may underestimate the effects of racial discrimination on health and ultimately lead to mixed results. Krieger cautions that differing self-reports of discrimination may be due to (1) internalized oppression, where members internalize negative views and messages about their intrinsic worth imposed from the dominant culture and (2) shaping answers to be “socially acceptable.” Self-reported measures also often fail to account for more macrolevel manifestations of racism.

Population-based approaches examine structural discrimination, which refers to the interaction of multiple macrostructural systems that independently and jointly assert bias to create discriminatory policies, practices, beliefs, and resource distribution to people in a social group. Given society's role in creating disparate physical and social environments, investigating community-level discrimination is equally as crucial as individual-level experiences. A recent systematic review evaluating area-level racial prejudice reported an association with adverse birth outcomes, increased cardiovascular disease, poorer self-reported mental and physical health, and higher mortality. Similarly, a recent scoping review evaluating exposure clusters of structural racism (e.g., access to healthcare, civil and legal system discrimination, housing and residential segregation, incarceration, structural violence, etc.) noted associations with infant health outcomes, chronic conditions, allostatic load, and quality of life.

Area-level racial prejudice has been examined using the General Social Survey, Project Implicit, Google Trends, and Twitter. Additionally, at least 73 measurement scales or indices of structural racism have been created with the Index of Concentration of Extremes, Dissimilarity Index, Everyday Discrimination Scale, Experience of Discrimination Scale, Five Segregation Scale, Index of Race Related Stress, Isolation Index, and Perceived Racism Scale considered the most commonly used. Residential housing patterns as an expression of structural racism are the most commonly evaluated, specifically through measurements of racial residential segregation and redlining. However, methodological challenges are still reported. The majority of studies investigating structural racism are cross-sectional, leading to limitations in temporality and inferences for causality. Existing measures of structural racism also primarily examine single dimensions of structural racism (i.e., housing, education, employment, incarceration). However, this approach fails to capture the multidimensional nature of structural racism wherein mutually reinforcing systems drive health inequities. Additionally, the extent of reinforcement among forms of structural racism is not examined.