Abstract
Objectives
To explore the relationship between self-regulatory coping behaviors (SRCB) and hypothalamic pituitary adrenal (HPA) stress reactivity.
Methods
Data came from the Richmond Stress and Sugar Study (n=125, median age: 57 years, 46% non-Hispanic White, 48% African American). The relationships between 11 SRCB (“health-harming” [e.g., smoking] and “health-promoting” [e.g., exercising]) with HPA stress reactivity, indicated by salivary cortisol response to the Trier Social Stress Test, was assessed using multi-level modeling.
Results
Health-harming and health-promoting SRCB were positively correlated (+0.33, p<0.001). Several individual behaviors were related to HPA stress reactivity, for example, smoking and meditation were associated with shallower increases in cortisol (smoking: −13.0%, 95%CI: −20.9% to −4.3%; meditation: −14.0%, 95%CI: −22.0% to −5.1%). However, SRCB summary measures were unrelated to stress reactivity.
Discussion
Health-harming and health-promoting SRCB are inter-related. Specific behaviors, rather than groupings as health-harming versus -promoting, are related to HPA stress reactivity.
“We believe that… the interrelation between physical and mental health disparities is about the utilization of stress coping mechanisms over the life course...We argue that poor health behaviors actually buffer the cascade of the effect of the chronic activation of the HPA-axis on psychiatric health disorders… The weak hypothesis [of the Environmental Affordances Model] says that poor health behaviors mask the stress response cascade that indeed creates the development of mental disorders. The strong one says that poor health behaviors through their actions on the HPA-axis and other brain hormones actually interfere with the cascade of neural and hormonal events that ordinarily would lead over time to mental disorders.” - James S. Jackson, Association for Psychological Science, 24th Annual Convention, May 24-27, 2012.
Introduction
Social scientists have long hypothesized that differential exposure to, and opportunities to cope with, chronic stress are fundamental processes underlying the emergence and persistence of racial and economic disparities in morbidity and mortality (Thoits, 2010). Additional scholarship emphasized the salience of “neighborhood” factors (e.g., cohesion, trust, and safety; greenspace, community resources, and walkability; area-level economic indicators) in shaping exposure and responses to stress (Barrington et al., 2014; Schulz et al., 2005). This work helped generate major improvements in the measurement of stress and in identifying contextual factors that shape the stress process (Turner et al., 1995). However, this research was largely uninformed by the parallel growth in understanding of the neurobiological stress response (i.e., hypothalamic–pituitary–adrenal (HPA) axis, sympathetic nervous system) (Miller et al., 2009), and the emerging appreciation of the salience of stress for reinforced and learned behaviors (Koob, 2008; Koob & Volkow, 2016). Dr. James S. Jackson sought to integrate these two lines of scholarship through his workgroup the Social Neuroscience of Health Disparities (SNOHD). Many of the activities of SNOHD were focused on elaborating and testing hypotheses informed by the Environmental Affordances (EA) Model of Health Disparities that James put forth in his writings and academic talks (Jackson et al., 2010; Jackson & Knight, 2006; Mezuk et al., 2010, 2013, 2017). This paper continues this line of inquiry by exploring the “strong” hypothesis of the EA Model that James described in his quoted speech above.
One of the most difficult challenges to the scientific study of stress as a determinant of health is the need to simultaneously integrate data on social, psychological, and biological aspects of the stress process (Nusslock & Miller, 2016). Even today there are few datasets that have robust measures across all three aspects of this phenomenon, particularly with sufficiently large samples of racial/ethnic minorities or lower socioeconomic groups, to permit testing hypotheses about how stress contributes to health disparities. Numerous studies have explored diurnal cortisol or multi-system indicators of physiology (e.g., allostatic load, telomere length) as indicators of the biological consequences of stress exposure (Castro-Diehl et al., 2014; Meier et al., 2019); however, these are not measures of the neurobiological stress response. While chronic stress exposure and acute stress reactivity are conceptually distinct, they are thought to be linked through both learned responses and physiologic processes over time (Chida & Hamer, 2008); however, the relationship between self-reported stress exposure and the acute stress response remains unclear (e.g., self-report chronic stress has been associated with both elevated and blunted cortisol response) (Do et al., 2011; Meier et al., 2019; Wells et al., 2014). As such the notion that “stress” is a key determinant of health disparities as a hypothesis still requires further exploration of the specific mechanisms driving this relationship.
There is also a need to critically evaluate the ways in which stress intersects with health behaviors like smoking, diet, physical activity, and alcohol use. First, move beyond models that treat behavior solely at the individual level by acknowledging that neighborhood context shapes opportunities to engage in behaviors, whether those are health-promoting (e.g., exercise) or health-harming (e.g., smoking). Second, move beyond the traditional approach of treating behaviors simply as “confounders” of the stress
The intersection of the stress process and self-regulatory behaviors sits at the center of the EA Model. Supplemental Figure 1 illustrates the model, with elaborations regarding the hypothesized mechanisms underlying each theorized path. Disparities in physical health are theorized to be shaped by differential exposure to chronic stress over the life course, in combination with greater engagement in “negative” health behaviors (i.e., tobacco use, poor diet, sedentary behavior). While differential exposure to chronic stress also shapes risk of poor mental health, the model argues for a more complex relationship for health behaviors and mental health outcomes. Specifically, the model hypothesizes that the same health behaviors that increase risk of medical morbidity long-term, when employed as self-regulatory, stress-coping behaviors, buffer the negative impact of chronic stress on mental health short-term. The “strong” hypothesis of this buffering effect is that it operates through neurobiological processes, predominantly the HPA-axis (Jackson & Knight, 2006). Analyses using independent samples have provided support for various paths of the EA Model (Boardman & Alexander, 2011; Jackson et al., 2010; Mezuk et al., 2010, 2017), although findings are not conclusive (Keyes et al., 2011) and the model is a subject of ongoing debate (Mezuk et al., 2021). In sum, while fundamentally situated within the social sciences, the EA Model provides an integrative, biologically informed, hypothesis-generating framework to guide interdisciplinary research on the ways that chronic stress and health behaviors contribute to mental and physical health, and health disparities, over the life course.
The goal of this paper is to examine one component of the EA Model by exploring the relationship between self-regulatory coping behaviors (SRCB) and the neurobiological stress response. This analysis uses data from the Richmond Stress and Sugar Study (RSASS), a racially and socioeconomically diverse cohort of adults at high risk of developing type 2 diabetes (T2D) that has robust measures of stress coping and the HPA-axis stress response. Together this makes the RSASS cohort an ideal setting for exploring questions related to the “strong” hypothesis of the EA Model articulated in the quote above: (1) Does the frequency of SRCB vary by neighborhood SES and race? and (2) Are SRCB associated with HPA-axis stress reactivity? While addressing these questions will not directly test the “strong” hypothesis in its entirety, this will be among the first efforts to examine the neurobiological stress response from the theoretical framework of the EA Model.
Methods
Participants were oriented to the scale with the following text (emphasis in original): “I will first ask you how often you do certain behaviors to cope after having what you think is a stressful event or day. I will then ask you how much that behavior reduces your feelings of being stressed.” This analysis focuses on the frequency of engaging in coping behaviors, that is, the response to the “how often” portion of the question. Frequency of using each SRCB was recategorized as a three-level variable (Never=0, Hardly ever/Not too often=1, and Fairly often/Very often=2) due to small cells. Beyond these indicators of each behavior, they were also summed to create three overall measures: (1) engagement in the six “health-harming” behaviors (median [IQR]: 4 [2, 5]), (2) engagement in the five “health-promoting” behaviors (median [IQR]: 8 [6, 9]), and (3) engagement in any of the SRCBs (median [IQR]: 11 [9, 13]).
Analysis
We first examined the distribution of SRCB as a function of neighborhood SES and race using chi-squared tests. The correlations of SRCB with each other, and with individual cortisol values from the TSST, were assessed using the Spearman method. Poisson regression was used to estimate whether the number of SRCB (total, health-harming, health promoting) varied by race and neighborhood SES after accounting for covariates.
We conducted exploratory data analysis including fitting locally estimated scatterplot smoothing curves (LOESS) to examine the cortisol response during the TSST. From this analysis, we determined that one linear spline knot at 45 minutes (time 4) since the start of the TSST was sufficient to capture the non-linear cortisol response. We used piecewise 2-level linear mixed effects models with an autoregressive correlation structure to examine the associations between the SRCB and three features of the salivary cortisol response across the TSST (baseline, increasing slope, and decreasing slope). Models included participant-level random intercepts and random slopes for the time spline, the main predictors, and their interactions with the time spline and were adjusted for age (mean-centered), sex, race, education (mean-centered), marital status, and neighborhood SES. To improve reliability of model standard errors, we used restricted maximum likelihood estimation (REML) and robust standard errors with bias correction (McNeish, 2017).
Cortisol values were log-transformed in all models to increase normality. Therefore, to improve model interpretability, the estimated coefficients were exponentiated and are interpreted as either geometric means or percent differences. Visually, for the increase in cortisol during the TSST, positive effect estimates indicate a steeper slope; for the decrease in cortisol after the peak, positive effect estimates indicate a shallower slope. Analyses were conducted using R (4.0.3) and all p-values refer to two-tailed tests.
Results
Demographic characteristics, health behaviors, and self-regulatory coping behaviors by race and neighborhood SES.
*Excludes n=7 participants who reported race other than Black or non-Hispanic white. p-Value for age, BMI, education, sedentary time, drinks/month, and sums of self-regulatory coping behaviors derived from Wilcoxon rank-sum test comparing medians. Household income missing data on n=3.
Frequency and perceived effectiveness of SRCB by race and neighborhood SES.
*Excludes n=7 participants who reported race/ethnicity other than NHW or AA.
Note. Perceived effectiveness imputed as “Not at all” for those who reported “Never” using a behavior.
As shown by Supplemental Table 1, SRCB generally had either null or positive correlations with each other, indicating that participants who engaged in “health-harming” behaviors were also likely to engage in “health-promoting” ones (i.e., r2 =+0.24, p<0.001 for meditation and eating sweet foods). Summing across all behaviors, the correlation between health-harming and health promoting behaviors was +0.33, p<0.001. Supplemental Figure 2 shows the relationship between the SRCB and their proxies (i.e., eating snacks and BMI, using distractions and sedentary time, seeking social support, and network size). It shows that while the SRCB are modestly correlated with their proxies they are not interchangeable.
Spearman Correlations of Frequency and Effectiveness of SRCBs with Salivary Cortisol during the TSST.
=p<0.05, **=p<0.01.
Model estimates for the panels of Supplemental Figure 3 of the relationships between individual SRCBs and proxy behaviors/characteristics with HPA-axis stress reactivity.
*The levels of all SRCBs are Fairly often/Very often (reference) versus Hardly ever/Not often versus Never. The levels of each related health behavior/characteristics are specified with that behavior and are operationalized in Supplemental Table 2.
To aid in interpretation, values in the table are shown as percent difference, and values in Supplemental Figure 2 are shown as log-transformed salivary cortisol. All estimates are adjusted for age, sex, educational attainment, marital status, and neighborhood SES.
Of those behaviors that had proxies, social support was the only instance where the SRCB was unrelated to stress reactivity, but the proxy was. Compared to those with a small family network, participants with the largest networks had 40% lower cortisol at baseline (−39.6%, 95%CI: −56.5% to −16.3%, p<0.003). Friend network size was unrelated to baseline cortisol but was associated with the TSST response: those with the largest friend networks had a higher rate of increase (14.9%, 95%CI: 3.3%–27.8%, p<0.01) and steeper decline (−3.9%, 95% CI: −8.5%–0.9%, p=0.11) than those with the smallest networks. For the three SRCB that did not have equivalents/proxies (e.g., Supplemental Figure 3 Panels Q to S: prayer, counselor/professional help, and meditation), only meditation was associated with HPA reactivity. Compared to those who never use meditation, participants who most frequently use meditation had a 14% shallower increase (−14.0%, 95%CI: −22.0% to −5.1%, p<0.003); estimates were similar but more modest for occasionally using meditation.
Discussion
This study explored the relationship between a range of SRCB and HPA stress reactivity in a racially and economically diverse sample of adults at elevated risk of developing T2D. The primary findings are four-fold: First, while not traditionally conceptualized as a means of self-regulating emotional distress, health behaviors related to eating, smoking, alcohol, and exercise are commonly reported as efforts to cope after a stressful experience. The frequency of engaging in SRCB does not differ substantially by race, with modest variation by neighborhood SES. Second, “health-harming” and “health-promoting” SRCB were positively correlated, indicating that individuals engage in a diverse set of behaviors. Third, while the summation indicators of SRCB were not associated with HPA stress reactivity, several individual SRCB, both “health-promoting” and “health-harming,” for example, both smoking and meditating, were associated with shallower increases in cortisol (i.e., weaker response) to the TSST. Finally, the analysis of proxy health behaviors and characteristics, assessed outside the context of stress coping, shows that the associations between the SRCB and HPA reactivity are broadly consistent, suggesting that it is the behavior itself, rather than the self-identified use of that behavior to cope with stress, that underlies the relationship between these indicators of self-regulation and HPA stress reactivity.
Consistent with prior work, engagement in “health-promoting” behaviors was positively correlated with engagement in “health-harming” ones. Such behaviors can be mutually reinforcing, as individuals who engage in more health-promoting behaviors may be doing so to compensate for past health-harming behaviors (Knäuper et al., 2004), and vice-versa as individuals who engage in more health-promoting behaviors may feel more comfortable engaging in health-harming behaviors (Mullen & Monin, 2016). Moreover, the null findings between the aggregate SRCB indicators and HPA reactivity are consistent with a recent longitudinal study that assessed the day-to-day relationships among promoting/harming behaviors with cortisol and found that positive behaviors, such as healthy diet and exercise, were either only weakly or unrelated to cortisol responses (Strahler et al., 2021). This suggests that the nature of the association between health-promoting behaviors (i.e., healthy diet, exercise, meditation) and HPA-axis functioning is better understood as one of a threshold, rather than dose-response, relationship (Pascoe et al., 2017). As a result, it may be more difficult to identify significant effects of such behaviors on neurobiology as they may only emerge after continuous and sustained engagement.
The EA Model situates social disparities within the Life Course Framework, noting that the relationships between stress, behavior, and health vary over time (Ben-Shlomo & Kuh, 2002). Timescale is also fundamental to the “strong” hypothesis of the EA Model regarding the consequences of stress and SRCB for mental versus physical health outcomes. The Model hypotheses that SRCB serve as a means to preserve short-term mental health in situations of chronic stress and few coping resources; while the exact time scale is still unclear, experimental evidence of stress reactivity and “health-harming” behaviors (i.e., consuming high fat/sugar foods, using nicotine or other drugs) suggests it may be on the order of hours, days, or weeks (Koob, 2008; Margittai et al., 2016). In contrast, the long-term physical health consequences of engaging in SRCB, whether those are “health-promoting” (e.g., exercise and meditation) or “health-harming” (e.g., tobacco and alcohol), are on the timescale of decades. Over those decades, not only do “health-harming” SRCB cause morbidity (i.e., diabetes, cardiovascular disease, cancer), but those morbidities in turn also negatively impact mental health. Drawing on the addiction perspective, it is likely that the relative effectiveness of SRCB to preserve mental health declines over time, much like the development of tolerance for psychoactive substances (Koob & Volkow, 2016). As such, over the life course, for social groups with higher exposure to chronic stress and ready access to health-harming behaviors, the stress-coping relationship changes from a zero-sum game concerning mental versus physical health to a lose-lose one.
As the name indicates, the EA Model provides a framework for generating hypotheses of how the connections between stress and self-regulatory behaviors, over the lifespan, contribute to disparities in mental and physical health as a function of factors like race, SES, and place. While not the focus of this analysis, it is important to be explicit as to the fundamental origin of these disparities: there is nothing biologically intrinsic about race, ethnicity, or social positioning as a cause of health disparities. Rather, because of systemic factors like racism, and discriminatory policies in political participation, housing, education, wealth distribution, criminal justice, etc., minority groups have been historically marginalized and disenfranchised (Williams et al., 2019). The legacy of these policies is evident today in neighborhood and school segregation, employment and wage gaps, mass incarceration, and access to quality healthcare. Leaders in the field have called for more structural, rather than individualistic, approaches to understanding race and racism as determinants of health (Neblett Jr., 2019). Given this fundamental origin of racial health inequities, what is the role of the neurobiological stress response in furthering our scientific understanding? As we have argued previously: “We believe that race, rather than a category of thingness, is actually a category of experiences... it is the accumulation of differential exposures and experiences associated with these categorizations that produces racial disparities in health over the life course” (Mezuk et al., 2013). It is from this foundation that the EA Model seeks to understand how adversities tethered to racial group membership and SES serve as conduits for life experiences, including those that involve the stress response.
Limitations and strengths. While the RSASS sampling frame was designed to decompose “race” and “place,” as a result it is non-representative (the Richmond, VA metropolitan area is approximately 57% NHW, 29% AA) (US Census Bureau, 2019) and lacks adequate representation of all racial/ethnic minority groups. While we sought to balance race groups on area-level SES, because of residential segregation this does not mean the contextual environments within stratum of neighborhood SES are equivalent for NHW and AA (Massey & Rugh, 2014). This analysis was limited to adults in middle-age, and future research on younger populations when health behaviors onset is needed to understand how these relationships emerge and change over the life course. This is particularly important given racial and SES differences in development of obesity in childhood and subsequent onset of T2D. This analysis tested multiple predictors of HPA reactivity, and the robustness of these findings needs to be confirmed in future research. Strengths of this study include direct measurement of the HPA-axis response to an acute stressor, a mechanism heretofore only hypothesized as central to the EA Model. Another strength is the comparison of many SRCBs to their equivalent health behaviors, of which only the latter have been widely used in tests of the EA Model to date.
These findings have implications for promoting health behavior change for adults at high risk of T2D like the participants in RSASS. Consistent with prior research (Nandi et al., 2014; Petrovic et al., 2018), participants from lower SES neighborhoods had higher BMI, were more likely to smoke, drink alcohol more frequently, spent more time sedentary, and were less likely to exercise, even if these differences were not all statistically significant. In contrast, we found that there was less variation in SRCB as a function of race or neighborhood SES. Rather, all groups, NHW and AA, and lower and higher SES, reported engaging in aggregate “health-harming” and “health-promoting” SRCB to similar degrees, even if they differed in specific behaviors. However, as posited by social science theory more broadly, norms and contextual factors influence behaviors, and thus these findings do not exclude culturally normative and nuanced reasons for the observed differences between specific behaviors (e.g., the salience of prayer as a coping mechanism among AA (Glover et al., 2019)).
When considering these findings in relation to individual health behavior change, it is important to consider the systemic and contextual factors that influence the options (affordances) within and across social groups. These findings, when viewed within the context of the SOBC Initiative, call for behavioral interventions that address how race, place, and SES combine to shape self-regulatory behaviors. Proposed interventions should incorporate indicators of stress response systems and seek to address the ways in which self-regulatory behaviors may be deterred or enhanced by cultural, environmental, social, and interpersonal factors.
Footnotes
Acknowledgments
This work would not have been possible without the mentorship of Dr. James S. Jackson. We are grateful to have been able to learn from him, and he is deeply missed. The authors would like to acknowledge the intellectual contributions of the SNOHD working group members who helped elaborate the EA Model over the years, particularly Jamie Abelson.
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The Richmond Stress and Sugar Study is supported by the American Diabetes Association (1-16-ICTS-082, to Mezuk). Additional support for this manuscript provided by the National Institute of Health through the Michigan Integrative Well-Being and Inequality Training program (R25-AT010664, to Mezuk) and the Michigan Center for Urban African American Aging Research (P30AG015281-21).
Author’s Note
For submission to the Journal of Aging and Health, Special issue honoring the work of Dr. James S. Jackson.
