Gratitude, social support and cardiovascular reactivity to acute psychological stress

https://doi.org/10.1016/j.biopsycho.2021.108090Get rights and content

Highlights

  • Gratitude and social support may influence cardiovascular reactions to acute psychological stress.

  • Gratitude was positively associated with systolic and diastolic blood pressure reactions to the stress task.

  • Social support was positively associated with total peripheral resistance(TPR) to the task.

  • The association between gratitude and TPR was mediated by social support.

Abstract

The pathways linking gratitude to cardiovascular reactivity (CVR) to acute stress are not fully understood. We examine whether this association is mediated by social support. Healthy adults (N = 178) completed measures of trait gratitude and perceived social support and participated in a standardised mental arithmetic and speech stress testing protocol. Their CVR (i.e., systolic and diastolic blood pressure [SBP, DBP], heart rate [HR], cardiac output [CO] and total peripheral resistance [TPR]) were monitored throughout. Gratitude was positively associated with SBP, DBP and TPR reactivity, with those reporting higher gratitude showing higher CVR. Social support was positively associated with TPR to the maths task. The association between gratitude and TPR was mediated by social support but this was only evident in response to the maths task and not the speech task. These novel findings suggest that CVR may be a potential mechanism underlying the gratitude-physical health link.

Introduction

An estimated 31 % of all global deaths annually are due to cardiovascular diseases, with 17.5 million people dying from coronary heart disease (CHD) alone (WHO, 2016). One factor, although often overlooked (Brown et al., 2019), associated with the onset and development of CHD is psychological stress (Dimsdale, 2008; DuPont et al., 2020; Steptoe & Kivimäki, 2013; Turner et al., 2020). Stress has been defined as an interaction between an individual and their environment with stress occurring when people perceive that the demands from external situations are beyond their coping capacity (Lazarus & Folkman, 1984). In terms of health impact, stress, in both childhood and adulthood, has been associated with ∼40–60 % excess risk of CHD (Steptoe & Kivimäki, 2012). In fact, there is a twofold increased risk of CHD among those reporting three or more childhood adversities compared with those reporting none (Scott et al., 2011). In adults, the impact of chronic stressors such as loneliness and social isolation on CHD mortality is comparable to that of established risk factors such as smoking (Holt-Lunstad et al., 2010). One of the proposed pathways linking stress to CHD is cardiovascular reactivity (CVR) to acute psychological stress.

The reactivity hypothesis (Obrist, 1981; Phillips & Hughes, 2011), proposes that exaggerated or prolonged CVR contributes to the manifestation of CHD in both adults (Brindle et al., 2018; Gianaros et al., 2002; Krantz & Manuck, 1984) and children (Roemmich et al., 2009). This hypothesis has received substantial support over the years (Chida & Steptoe, 2010) with prospective studies finding that exaggerated reactivity to stress is associated with adverse cardiovascular outcomes including hypertension (Carroll, Ginty, Painter, et al., 2012), atherosclerosis (Barnett et al., 1997; Matthews et al., 1998), and mortality (Carroll, Ginty, Der, et al., 2012). However, recent research suggests that relatively low CVR to stress also has adverse health associations including obesity, depression, and addiction (e.g. smoking, alcohol) (Phillips & Hughes, 2011). These are also linked directly and indirectly to CHD through pathophysiological mechanisms (De Hert et al., 2018). Identifying positive psychosocial factors that may mitigate atypical stress reactions has been a focus of considerable research (Bajaj et al., 2019; Fredrickson, 1998; Fredrickson & Levenson, 1998; Kok et al., 2013; Puig-Perez et al., 2017).

One such factor which has attracted a growing level of interest for physical health and biological processes is gratitude (Jans-Beken et al., 2020; Park et al., 2014; Schache et al., 2019). Gratitude is conceptualized as a broad dispositional orientation towards perceiving and appreciating the positive in life (Wood et al., 2010). Dispositional gratitude is usually assessed by the GQ-6 with no specified time limits, whereas state gratitude can be captured by the gratitude adjective checklist (GAC) using a more limited timeframe (Froh et al., 2011; McCullough et al., 2002). In terms of physical health, gratitude has been associated with reduced physical symptoms as indexed by reduced headaches, muscle fatigue, and feelings of nausea (Emmons & McCullough, 2003) as well as better cardiovascular health (Jackowska et al., 2016; Mills et al., 2015). Recent research has begun to examine the direct physiological effects of gratitude as a way of understanding its implications for physical health. For example, heart failure patients who participated in a gratitude intervention had reduced inflammation and increased parasympathetic heart rate variability compared to those in the control group (Redwine et al., 2016). Similarly, in a study of pregnant women, gratitude journaling reduced the stress hormone cortisol (Matvienko-Sikar & Dockray, 2017). In fact, these studies are in line with current theory on positive emotions which are considered to be a buffer against the negative effects of stress (Folkman, 2008; Levenson, 2019; Pressman et al., 2019).

A grateful response to life circumstances is considered a fundamental process by which everyday experiences are positively interpreted (Emmons & McCullough, 2003). As such, gratitude as a positive emotion may facilitate how people deal with, and manage, stress (Folkman, 2008). Research examining gratitude as a buffer of cardiovascular stress reactivity is limited; however, one recent study reported that state, but not trait, gratitude was associated with lower CVR to a mental arithmetic stress task (Ginty et al., 2020). A similar finding was also recently reported, with state-like gratitude proving most predictive of lower CVR (Gallagher et al., 2020), indicating it may be a stress buffer. However, this study had a relatively small sample, and the underlying hemodynamic variables (i.e., cardiac output [CO] and total peripheral resistance [TPR], which are fundamental to obtaining greater insight into the pathophysiology of hypertension) (Pollock et al., 2020), were not examined. Moreover, reduced TPR and increased CO have been associated with emotional and social factors (Brown et al., 2019; Weisbuch et al., 2009) and so may be relevant to the present context. Thus, given the call for researchers to examine the pathways underling the gratitude-health link (Jans-Beken et al., 2020; Schache et al., 2019) and the paucity of research in the area, further research into the influence of gratitude on CVR to acute stress is needed.

Gratitude has also been found to reduce feelings of social isolation (Frinking et al., 2020) and enhance social relationships (O’Connell et al., 2017). Similarly, those expressing gratitude towards others in diaries were found to have increased relationship satisfaction relative to active controls (O’Connell et al., 2016). Other studies have found that gratitude fortifies existing relationships by fostering social bonds and socially inclusive behaviours (Bartlett et al., 2012), and encourages relationship formation and connections (Algoe, 2012). Thus, it might be that gratitude is influencing CVR via social support which has known associations with CVR (Gallagher et al., 2014; Uchino, 2009).

Social support is the processes by which social relationships promote health and well-being (Cohen, 2004). A meta-analysis examining experimental manipulations of social support (e.g., provision of active or passive support compared to no support) on CVR to laboratory stress found that it was associated with reduced hemodynamic reactivity (Thorsteinsson & James, 1999). In line with this notion, perceived social support in real life was associated with lower cardiovascular responses to a stress task (Howard et al., 2017; O’Donovan & Hughes, 2008). Moreover, social support is a multi-dimensional construct including instrumental, tangible and emotional facets, with emotional support viewed as more nurturing than either informational or tangible support (Trobst, 2000). Emotional support also has stronger cardioprotective effects (Horsten et al., 2000). While the stress-buffering effect of manipulated social support on CVR has been extensively researched (Gallagher et al., 2014; Holt-Lunstad et al., 2008; Uchino, 2006; Uchino et al., 1996; Uchino et al., 2011) little research has been conducted on the effects of perceived availability of social support.

Gratitude is seen as a social emotion (Emmons & McCullough, 2004) and such emotions help us connect with others (Petersen et al., 2019). As such, gratitude might increase perceptions of social support. At least two recent studies are consistent with this idea. First, social support was identified as a mediator of the association between gratitude and depressive symptoms, such that those higher on gratitude reported higher social support and lower depression (McCanlies et al., 2018). Second, lower loneliness and lower perceived stress were found to be sequential mediators of the association between gratitude and physical health symptoms. Those higher on trait gratitude, reported less loneliness, perceived the stress in their lives to be lower, and had better physical health. Based on the above evidence it is plausible that the association between gratitude and CVR may be mediated by social support such that those reporting higher gratitude will also report higher social support and subsequently have lower CVR to acute stress. This fits with calls to examine the links between gratitude (Park et al., 2014), social support (Uchino et al., 2012), and physical health.

One limitation of previous research investigating the association between gratitude and CVR is the use of a largely asocial stress task by some (Gallagher et al., 2020) and a more social task by others (Ginty et al., 2020). The social context of a stress-task can be an important moderator of the relationship between psychological factors and CVR. For example, socially relevant personality traits such as Type D, show differing associations depending on the social nature of the task (Bibbey et al., 2015; O’Riordan et al., 2019). Loneliness, also a construct that reflects a social dimension, has shown differing associations with CVR depending on whether the stressor was social or asocial (Brown et al., 2019). Therefore, it remains to be established if observed associations between gratitude and CVR generalize across both asocial and social contexts within the same study.

Therefore, our aim is to replicate and extend limited prior research evaluating associations between gratitude and CVR to both social and asocial stressors by evaluating the same association across two different stress tasks; social and asocial. We hypothesized the following: 1) both gratitude and social support are inversely associated with CVR to acute psychological stress and that these effects are more pronounced for the asocial task; and 2) the association between gratitude and CVR is mediated by perceived social support.

Section snippets

Participants

Data were collected from 178 healthy adults (63.5 % female), recruited from a university setting over an 18-month year period starting in October, 2017. G-power calculations confirmed that a minimum sample size of 146 participants was needed to detect a significant effect (p =  .05, f²=0.06) at 80 % power. The present manuscript is part of a larger study observing demographic and psychosocial factors associated with cardiovascular responses to acute psychological stress. Participants were

Descriptive statistics

Descriptive statistics for psychological and cardiovascular variables are reported in Table 1. Trait gratitude scores are similar to other studies in young adults (O’Connell et al., 2016) and our social support mean score is higher than found elsewhere (Cyranowski et al., 2013). The correlation between support and gratitude was r = .23, p = .003, with higher levels of social support associated with higher gratitude. While there was no difference in gratitude score between men and women, men

Discussion

Our aims were to build on previous research on gratitude and its associations with CVR to acute stressors, testing to see if perceived support was as a mediator of this relationship. Although we found that both gratitude and perceived support were associated with some aspects of CVR, these associations were not observed across all measured indices. Contrary to our hypotheses, both constructs were positively, rather than negatively, associated with CVR; those reporting higher gratitude had

Funding

The authors received no funding for this research.

Declaration of Competing Interest

The authors report no declarations of interest.

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      It is worth noting that to our knowledge, no other study has examined how gratitude impacts cardiovascular recovery. While previous research has noted the effects of state gratitude on cardiovascular reactivity to stress (Gallagher et al., 2020, 2021; Ginty et al., 2020), no other study has examined the recovery period. Considered in the light of research indicating that exaggerated responses to stress are associated with negative cardiovascular health outcomes (Chida and Steptoe, 2010; Treiber et al., 2003), this implies that state gratitude has an important stress-buffering function.

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