Evidence linking social support to blood pressure

Social support encompasses both the quality and quantity of a person’s social contacts and support (including emotional support). Research shows that low levels of social support are associated with all-cause mortality and other adverse health outcomes. And there is evidence that social support has specific effects on cardiovascular health (Birmingham et al., 2023) , and high levels of social support are associated with lower risk of incident hypertension (Harding et al., 2022) .

The quantity and quality of social ties impact mental health, physical health, health behaviors, and mortality risk. Compared to their more isolated peers, socially connected individuals tend to live longer and healthier lives. Several studies illustrate that low quantity or quality of social ties increases the likelihood of cardiovascular disease, atherosclerosis, recurrent our ocardial infarction, autonomic dysregulation, cancer, and hypertension (Uchino, 2006; Ertel et al., 2009) . Racialized differences in social ties might be causal factors behind racial differences in cardiovascular disease.

Data show that married adults experience lower rates of mortality and morbidity than unmarried adults, and married individuals report greater satisfaction with life, more happiness, and lower risk of depression (Lawrence et al., 2018) . But interestingly, this is a gendered effect, as research suggests that married men are less likely to have hypertension, while single and never-married women are less likely to have hypertension (Azizi et al., 2022) . Among the benefits of marriage in terms of regulating blood pressure, being married can help reduce certain risky health behaviors tied to increased blood pressure. Spouses can also help one another in managing their hypertension medication (Wu et al., 2012) making important dietary changes (Gallant et al., 2007) and encouraging healthy lifestyles (Gorin et al., 2008) . Because US Black women are much less likely to be married compared to White women across multiple age groups (US Census Bureau, 2020) , fewer Black women are to take advantage of the health-protective benefits of marriage.

Recent research has shown that volunteering has a positive effect on both mental and physical health. For instance, it offers opportunities to enhance social networks, connectedness and social bonds (Milbourn et al., 2018) . According to Sneed and Cohen (2013) , older adults were at a significantly lower risk of developing hypertension if they performed 200 hours or more of volunteer service in the past year. And at a 4-year follow-up, participants who engaged in volunteer activities had 40% lower odds for incident hypertension than those who did not volunteer, and this association was independent of race, age, baseline health, sex, education, marital status, baseline blood pressure, and other variables. Studies show consistent racialized volunteering practices among Americans, whereas Whites are more likely than Blacks to volunteer (Wray-Lake & Hart, 2012) .

Evidence linking psychosocial factors to blood pressure

The effects of psychosocial risk factors on health, and on blood pressure in particular, are well documented. Research shows that they may influence health either directly, through biological responses to stress, or indirectly, through health-related behaviors (Siegrist & Marmot, 2004; Cuevas et al., 2017) . Studies generally indicate that favorable psychosocial conditions are related to better heath, while poor conditions are damaging to health and contribute to health inequalities (Kivimäki & Steptoe, 2018) , and there is ample evidence that multiple psychological and social factors contribute to the onset of and trajectory of hypertension (Cuevas et al., 2017) . In fact, emotional stress can induce a physiological response that triggers activation of the sympathetic nervous system, inflammation, and the hypothalamic-pituitary-adrenal axis (Spruill, 2010) . When this occurs repeatedly, it is difficult for blood pressure to return to resting levels, and over time, this process is associated with increased blood pressure over time, higher circulating levels of catecholamines, and higher cortisol levels (Everson-Rose & Lewis, 2005) .

Data show that Blacks in the US experience negative psychosocial influences more often than Whites. In fact, extant research suggests that racial differences in psychosocial stress, brought about by difficult conditions commonly experienced by Blacks in the US (Hill & Thayer, 2019) , including denial of respect, experiences of loss or failure, lack of common dignity and courtesy, and being perceived as inferior, may plausibly mediate associations between race and blood pressure (Cogburn, 2019) .

Several studies have provided convincing evidence for the causal link between depression and hypertension. For example, using NHANES follow-up data, early research by Jonas, Franks, and Ingram (1997) found that anxiety and depression are associated with a markedly increased risk of hypertension among both Blacks and Whites. But the increase in risk was not equivalent, as it nearly doubled for Whites, but almost tripled for Blacks (Jonas et al. 1997) . This was the first prospective study to show that anxiety and depression can predict hypertension many years into the future. In a subsequent study, Jonas and Lando (2000) found that hypertension was influenced by negative affect among several groups, but its predictive power was greatest among Black women. Other independent studies have provided support for increased risk of hypertension development among those with higher levels of depression (Alhawari, AlShelleh, Alhawari, Akiely, Abdallah, Hajjaj, Alkhalaileh, & AlRyalat, 2022) .

Extant research links hypertension with certain personality traits. For example, neuroticism, which is associated with coping style, has consistently been found to be associated with hypertension (Arroyave-Atehortua, Cordoba-Sanchez, & Cruz, 2023; Syk, Isaksson, Rasmusson, Ekselius, & Cunningham, 2021) . Chronic anger often includes hostility, which consists of cynicism and mistrust. Hostility has predicted elevated blood pressure in various studies, and many have reported that it is an independent risk factor for coronary heart disease (Körösi, Vecsey-Nagy, Kolossváry, Nemcsik-Bencze, Szilveszter, Laszlo, Batta, Gonda, Merkely, Rihmer, & Maurovich-Horvat, 2019) .

Research suggests that both the psychological and physiological responses to discrimination are comparable to those of other psychosocial stressors (Vines, Ward, Cordoba, & Black, 2017) . For example, exposure to racist acts via viewing videos of discriminatory behavior in a laboratory setting is associated with psychological reactivity and increased cardiovascular responses among Blacks (Jones et al., 1996) . People of color often encounter racial and ethnic discrimination in their daily activities, such as when they seek health care (Mays et al., 2017; Nong et al., 2020) , attempt to purchase or rent a house (Kijakazi et al., 2019; McCargo & Choi, 2020) , apply for jobs (Quillian et al., 2017) or public assistance (Barnes & Henly, 2018) , and interact with law enforcement (Alang et al., 2017; Bui, Coates, & Matthay, 2018) . These experiences, individually and cumulatively, cause physiological stress responses, and facing chronic exposure to these forms of racism can have serious negative effects on mental and physical health (Brondolo et al., 2011; Miller et al., 2021) .

Research has detected significant associations between religious involvement and blood pressure (Cozier, Yu, Wise, VanderWeele, Balboni, Argentieri, Rosenberg, Palmer, & Shields, 2018) . Higher degrees of religiosity and spirituality (Brewer, Bowie, Slusser, Scott, Cooper, Hayes, Patten, & Sims, 2022) and religious coping (Steffen et al., 2001; Cozier et al., 2018) are all associated with lower odds of hypertension. Further, people who indicate higher levels of religious involvement tend to have lower SBP and DBP and a decreased risk of hypertension (Buck et al., 2009; Skipper, Towns, Moye, & Rose, 2022) . Others find that frequency of attendance at religious services inversely affects the odds of hypertension (Gillum & Ingram, 2006) . Also, engaging in various religious activities, such as praying, are associated with lower blood pressure (Brasileiro, Prado, Assis, Nogueira, Lima, & Chaves 2017) . Interestingly, studies find that this effect can be racialized, as church attendance and religiosity seem to be more likely to affect blood pressure for Black Americans compared to Whites (Brown, 2006; Oates, 2013) .

Evidence linking contextual factors to blood pressure

Research suggests that enduring contextual, or environmental, stress is associated with the development of hypertension through a variety of pathways. Brown, Hill, and Lambert (2005) examined associations between intimate violence, community violence, and mental health among a group of urban Black women and found that exposure to community violence (witnessing and victimization combined) was significantly related to traumatic stress symptoms. They also found an interaction between intimate partner violence and community violence so that women with exposure to both types of violence had increased rates of traumatic symptoms, relative to women with exposure to only one type of violence. This suggests that exposure to violence in multiple contexts is extremely damaging to health (Brown et al., 2005) .

Black people represent about 13% of the population in the United States, of which 61.2% are members of the middle class (Perry & Romer, 2020) . As we discuss contextual factors, many of the Blacks in the middle class live in less segregated communities when compared to those in the lower class. In fact, many middle-class Blacks tend to live around less affluent whites as a result of residential economic discrimination, and structural discriminatory practices (Quick & Kahlenberg, 2019) .

As residential economic discrimination is problematic, Blacks in the US are at an increased risk of exposure to stressful environments, including disadvantaged neighborhoods that are entrenched with forms of hostility that are structurally driven. In fact, Blacks have higher overall lifetime rates of exposure to neighborhood violence than almost all other racial groups (Maly & Vallerand, 2018) . One reason behind this racial difference is that levels of violence are higher in areas that are disadvantaged and residentially unstable because such environments encourage criminal and violent acts. Also, these areas tend to lack social control mechanisms that normally discourage violent crime because it is difficult for these types of communities to organize around common goals and facilitate the control of violence (Peterson & Krivo, 2009) . Thus, the disadvantaged neighborhood and residentially unstable areas that Black citizens live in are all faced with residential segregation and contemporary acts of racial discrimination, residential economic discrimination, and other social phenomenon driven by forces of structural racism such as gentrification, fewer options of opportunity, educational disparities and wealth gaps that further contributes to stressful environments (Quick & Kahlenberg, 2019) . Consequently, many of these factors contribute to worsened health outcomes.

The traditional explanation for disparities in hypertension between Black and White women concerns differences in socioeconomic status and/or health behaviors. But, as indicated above, these disparities in blood pressure remain after controlling for such factors. More recent research on racial health disparities has begun to examine other variables, such as social support, religiosity, exposure to violence, stress, and access to health care. To our knowledge, no previous research has examined cross-sectional effects of social support, psychosocial characteristics, and contextual factors on disparities in hypertension between Black and White women in one model.

The purpose of this study was to examine the effects of social support, psychosocial characteristics, and contextual adulthood factors on hypertension. In this nationally representative sample of young American adults, we found that the prevalence of prehypertension, hypertension I and hypertension II was higher among Black women than White women. Despite the substantial differences in SES between the two racial groups, adjustment for current SES did not account for racial differences in blood pressure. And adjustment for other factors associated with blood pressure did not substantially diminish racial disparities in blood pressure either.

Although adulthood social support factors helped diminish slight amount of racial disparities in blood pressure, the association between race and blood pressure remained largely unchanged after adjustment for social support (Model B). None of the psychosocial factors (Model C) reduced blood pressure disparities; in fact, they caused them to widen. In all, only the model including BMI helped explain a non-negligible portion of the disparities in prehypertension or hypertension between Black and White women. Indeed, of all the variables considered in our analyses, the only three that clearly and consistently affected the odds of hypertension were race, age and BMI. So, being Black, as opposed to being White, increased age, and being obese, rather than having a lower BMI, were all positively and significantly associated with blood pressure.

High BMI is a major cause of hypertension. Many studies, including this one, have shown strong associations between overweight and obesity, and increased risks for prehypertension and hypertension. Interestingly however, even after controlling for BMI, Black women remain at greater risk than White women for prehypertension and hypertension. Other research (Fei, 2017) has found that Blacks have higher prevalence of hypertension than Whites at every level of BMI, possibly suggesting the importance of race-specific BMI cutoffs to more accurately assess obesity-related risks of hypertension across groups. Young et al. (2018) also reported that, controlling for BMI, Blacks had significantly higher blood pressures than Whites. These findings indicate complex relationships between race, blood pressure, and obesity that should be examined more thoroughly. The stronger association between obesity and prehypertension among Whites in our study suggests that factors other than BMI are affecting blood pressure among Black women, putting them at higher risk of prehypertension than their White counterparts at the same BMI level.

Extant research shows that various social support factors, including greater functional social support (Harding et al., 2022) and frequent contact with friends (Gorman & Sivaganesan, 2007) , are negatively associated with blood pressure. Others have reported that volunteering is significantly associated with lower blood pressure among Whites, with no such association among Blacks (Tavares et al., 2013) . Research also shows that psychosocial factors, including depression (Troxel, 2003; Zhong et al., 2017) , and perceived lifetime discrimination (Forde et al., 2021) , and contextual factors, such as violent neighborhoods (Clark et al., 2007) , are linked with hypertension. The fact that these factors did not diminish racial disparities in prehypertension or hypertension in our study suggests that other social support factors may be important to consider. For instance, these models do not include a measure of relationship or marital quality.

Our models also do not account for John Henryism, a style of coping used to deal with psychosocial and environmental stressors such as racism and career problems common among goal-oriented Blacks who lack resources such as financial or emotional support needed for success (Nguyen et al., 2021) . Other studies have linked John Henryism to stress and increased blood pressure (Holt-Lunstad et al., 2008) , while other studies do not support such a link (Barajas et al., 2019) . Other research reports a prevalence of higher blood pressure among those experiencing John Henryism in lower resource neighborhoods compared with those of higher resource neighborhoods (Brody, Yu, Miller, Ehrlich, & Chen, 2018) . It is likely that other measures of social support, as well as other aspects of psychosocial health and environmental context, are behind some of the racial differences in blood pressure.

The lack of substantial reductions in racial disparities in the odds of prehypertension and hypertension, even after accounting for social support, psychosocial characteristics, contextual factors, and proximate determinants (BMI and smoking), could suggest that simply being a Black woman in the US is associated with poorer health, including increased blood pressure. It is widely known that Black women generally face more pressures, stresses, and obstacles than their White counterparts. They experience more interpersonal, institutional, structural, disciplinary, and ideological racism than most other women (Collins, 2009; Alson, Robinson, Pittman, & Doll, 2021) . In fact, the term misogynoir was developed by Bailey to describe the specific distrust, hatred, dislike, aversion to, and prejudice directed toward Black women in the United States (Bailey, 2021) .

Various forms of racism work together to legitimize and to reinforce inequality and unfairness in all domains in society. For instance, racism institutionalized in the educational system, healthcare system, legal system, and so on, place Black women at a disadvantage in educational attainment, income, and other social determinants of health (Hill, Ndugga, & Artiga, 2023) . This fosters a stressful living environment for Black women, producing psychological and physiological effects related to racism and the minority and subordinate status held by many Black women in the US. In other words, racism in each domain, and in society as a whole, may have a cumulative effect on the health and well-being of Black women, likely increasing blood pressure and other stress-related symptoms. So, simply being a Black woman in US society is arguably unhealthy due to interpersonal and structural racism and its insidious effects. The health effects of racism are not easily measured by social science research, which is possibly why racial blood pressure disparities have yet to be explained.

Biological explanations for racial differences in health have generally been dismissed by social scientists, but this study suggests that some of these explanations should be taken more seriously. Over the past few decades, biological research has begun to transform the debate on the origins of health disparities. Relatively recent evidence, including research linking low birth weight to increased risk of cardiovascular disease, has led to new ideas about the effects of the prenatal environment on adult health (Leeson et al., 2001) . It is now known that the prenatal environment, along with economic, social, and nutritional factors of pregnant women, affect the adult health of unborn children. Such evidence suggests that some disease etiology may be traced to the intersection of biology and the environment. This type of factor is triggered by the environment and manifests as developmental plasticity in the function and structure of tissues, organs, and biological systems (Kuzawa & Sweet, 2008; Schell et al., 2020) .

Because these factors implicate changes in early developmental processes, they can have longer-lasting impacts on adult biology and health than the adulthood environment, which is often transient. Tracking adult disease risk to prenatal and early childhood origins generates new theories about the causes of human biological variation, including that related to race and health (Kuzawa & Sweet, 2008) . According to the Barker hypothesis, the effects of prenatal and neonatal factors, such as low birthweight and slow fetal growth, as well as postnatal development, are influenced by environmental factors and developmental paths that precede and follow them (Gowland, 2015) .

These processes can help illuminate how early life exposures, such as stress, can produce a phenotypic memory that persists through the life-course to influence adult physiological function, health, and risk for disease (Jirtle & Skinner, 2007) . Such findings are beginning to reframe the study of biology and health as life-course phenomenon, with early life and life-course environments and experiences of prior generations, affecting adult outcomes (Kuzawa & Sweet, 2008; Gowland, 2015) .

Further, research in epigenetics is demonstrating that environmental factors can modify epigenetic processes, thereby impacting epigenetic marks and downstream patterns of genetic expression in particular cells and cell lineages. This line of research shows that, by linking maternal and intergenerational experience with fetal biology, stressors, such as psychosocial and financial stress or imbalanced nutrition, can alter biological settings in children, with long-term health implications. These effects can include physiological responses to stress and blood pressure regulation (Kuzawa & Sweet, 2008) and even depression (Park et al. 2019) . So, the study of epigenetics indicates that, in addition to the chronic and cumulative health impacts of social environments, there is a strong motivation to consider a developmental influence and intergenerational impacts on patterns of adult health disparities (Kuzawa & Sweet, 2008) , including those related to blood pressure and hypertension. It is likely that such processes are behind some of the health disparities seen between Black and White women.

Stress is a major contributor to the development of hypertension, and in the United States, Black women tend to live more stressful lives than do White women. Social support, psychosocial factors, and contextual factors can be direct contributors to stress and physiological reactions to stressful experiences, and they can also serve to mitigate and moderate other life stressors. Further, all these factors influence one another. It is also crucial to explore risk factors for hypertension and other cardiovascular diseases that affect different groups differently. For instance, recent research suggests that lifelong discrimination is a major chronic stressor and that it is linked with hypertension in Black Americans, but not so much in other minoritized racial groups. Discrimination can come in many forms and from many sources, such as institutional racism, structural racism, and interpersonal racism, each with different impacts on physical health. Further, not everyone has the same resources and support factors to help deal with the effects of discrimination. It is possible that actual and perceived discrimination are especially harmful to Black women because they might be more densely intertwined into their lives, and they might experience them at more and varied levels. For instance, Blacks in the United States are especially susceptible to perceiving and experiencing workplace racial discrimination (Gallup, 2020) , discrimination in hiring practices (Restaurant Opportunities Centers United, 2020) , discrimination in house appraisals (Kamin, 2020) , discrimination in health and health care (Ndugga & Artiga, 2021) , and a host of other sources. So, establishing the precise effects of perceiving discrimination on health is difficult and complicated because many types of discrimination carry with them effects that impact health and health resources.

Social and structural discrimination in the U.S., for example, Blacks, women, and people in poverty are more likely to experience physiological responses to discrimination and environmental factors, like air and water pollution, that can contribute to poor cardiovascular health. That is, because different groups, such as intersectional minorities (i.e. Black women in the US), are exposed to and affected by social, structural and environmental factors differently, research that targets differential influences and their impacts on health among each group is necessary to reduce poor health among all US social groups. It will not be possible to effectively combat dangerous health disparities until we can better understand the numerous and complicated factors involved in these inequalities on an individual, as well as an intersectional basis.