Psychophysiological Aspects of Stress Essay

Stress seems to be an unpleasant, but essential part of human life. Adverse events happen in life, and hardly anyone is an exception. However, the same negative life events may result in different outcomes depending on the individual who faces them. To paraphrase the common words, â€Å"what doesn’t kill you (just) makes you stronger†. The question of what inner resources help one cope with stressful â€Å"lemons† in one’s life, and perhaps, â€Å"make lemonade† out of them has long attracted attention of philosophers, writers, moviemakers, and at some point every person who has experienced negative life events. It is not surprising that the issue of individual differences in response to stress has been extensively explored in psychology. Individual differences may vary from situational resources, such as social support, to personal resources, such as certain personality traits (e. g. , hardiness, explanatory style, optimism, self-esteem, psychological control, etc. ) These psychosocial resources strongly influence both psychological and physiological outcomes of stress. The Alameda County Study showed that those people who had more ties to their community and social network lived longer (Berkman & Syme, 1979). Receiving social support helped women with ovarian cancer cope with their illness better (Costanzo et al. , 2005), whereas social isolation strongly increased the likelihood of stroke recurrence in patients with stroke (Boden-Albala, 2005). Lack of social support strongly predicted elevated levels of anxiety and depressed mood (Godin, 2004). Personality resources may also help people cope with stressful life events. For example, optimistic explanatory style was associated with significantly fewer physical complaints in college students (Carver & Scheier, 1999), whereas pessimistic explanatory style increased symptoms of depression (Bennett & Vanderbilt, 2002). Perceived control also appears to mitigate the effects of stressful life events (Frazier, 2004). Finally, almost 3 decades of research on the moderating effect of hardiness has linked this personality resource to physical and mental health (Maddi, 1999). Specifically, hardiness is associated with fewer symptoms of depression (Oman, 2003) and burnout (Cilliers, 2003), and it physical strain as well (Beasley, 2003). The list of personal and situational resources moderating the effect of adverse life events is far from being complete; in fact, it may be quite extensive. Given the strong moderating effect of psychosocial resources on mental and physical health established by the previous research, the questions that arise, such as how exactly do these resources affect health? Are there any physiological differences in the way those individuals who have more psychosocial resources, and those individuals who have fewer resources, react to stress? The present study aims to answer this question with regard to the effect of personality hardiness on physical outcomes of stress. Research has shown that hardy individuals appear to thrive on stressful life events (Maddi, 1999). Hardy individuals are committed to their work and family, they perceive control over their life circumstances, and they perceive stressful life events as an opportunity for growth and development, rather than a threat (Maddi, 2002). Hardiness is an important moderator of stress response, yet little research has investigated the differences in the physiology of stress responses in high hardy versus low-hardy individuals. Previous research found that increased physiological reactivity to stress (for example, in terms of blood pressure) is associated with detrimental health outcomes, such as hypertension. However, hardiness has been strongly linked to better health outcomes of stress (Beasley, 2003; Cilliers, 2003; Maddi, 2002, Oman, 2003). Previous research has also shown that identical blood pressure increases can be produced by different hemodynamic mechanisms, with negative or neutral implications for health (Sherwood et al. , 1999). The goal of the present study is to clarify how hardiness takes its effect on health in terms of the psychophysiology of human stress responding. The Biopsychosocial Model of Challenge and Threat In this paper, the physiological response to stress is conceptualized within the biopsychosocial model of challenge and threat paradigm developed by Blascovich, Mendes, Tomaka, and colleagues (Blascovich, Mendes, Tomaka, Salomon, & Seery, 2003; Seery, Blascovich, Weisbuch, & Vick, 2004). In a series of studies, Blascovich, Tomaka, and colleagues demonstrated that threat and challenge appraisals are associated with distinctive patterns of cardiovascular response during a goal-relevant, motivated-performance task (Blascovich et al. , 1999). In Obrist’s terms (1983), this type of task involves active coping. In order to evoke both challenge and threat reactivity, the task should be engaging and psychologically involving, such as taking a test, making a good impression, giving a speech, and engaging in athletic competition (Seery et al. , 2004). Challenge appraisals are associated with positive affectivity, greater engagement in the situation, and are mediated by the myocardial response; whereas threat appraisals are associated with negative affectivity and blood pressure responses that are mediated by the vascular resistance. Challenge and threat are distinguished by changes in total peripheral resistance (TPR; the index of net constriction of the blood vessels) and cardiac output (CO; the amount of blood pumped by the heart per minute). In relative terms, greater CO and lesser TPR reflect greater challenge/lesser threat response profile. According to biopsychosocial model, threat reactivity is associated with detrimental health outcomes of stress. Blascovich and colleagues tied Lazarus and Folkman’s (1984) transactional model of stress and coping to physiological response to stress in terms of myocardial and vascular hemodynamic profiles. According to Lazarus and Folkman (1984), when the individual confronts new or changing environment, he/she tries to determine the meaning of the event (â€Å"primary appraisal†). Primary appraisal is concerned with whether the event is likely to be neutral, positive, or negative in its consequences. Negative events may be appraised in terms of future damage potentially produced by the event (â€Å"threat†), or as damage that has already been made by the event (â€Å"harm†), or in terms of one’s potential to overcome the event and perhaps even benefit from it (â€Å"challenge†). Secondary appraisal is concerned with the evaluation of whether one’s resources are sufficient to meet the threat, harm, or challenge. The balance between the primary and secondary appraisal determines one’s experience of stress. Blascovich and colleagues (Blascovich et al. , 2003) conceptualized threat/challenge essentially in terms of the ratio between the primary appraisal and secondary appraisal. In addition, in their approach, primary appraisal involves estimations of danger, uncertainty, and required effort. Danger, uncertainty, and effort define how demanding the situation is. The subjective experience of stress then depends on the ratio between the demand and one’s coping resources. If the demand is high, and the resources are low, the individual feels threat. If the demand is high, but at the same time the coping resources are sufficient to meet it, the individual feels challenge. Threat appraisal implies the aversive experience in that the individual anticipates damage from the situation, and presumably experiences negative affectivity, such as fear, anxiety and anger. In contrast, challenge appraisals are considered less aversive, with a primary focus on the potential for growth or gain that can come from the situation, although damage is also possible. Challenge appraisals are therefore theoretically associated with increased motivation and positive affectivity, such eagerness, excitement, and exhilaration. To reiterate, it is the threat appraisal that primarily accounts for perceived stress (Tomaka & Palacios-Esquivel, 1999). Blascovich and colleagues conceptualize threat and challenge as two opposite points on the single appraisal continuum. This is also different from Lazarus and Folkman’s conceptualization of threat and challenge as not mutually exclusive appraisals. Lazarus and Folkman’s (1984) concept of appraisal has come under considerable criticism (Zajonc, 2000). Zajonc believes that cognitive appraisal and affective experience are â€Å"distinct, conceptually separable processes† (Zajonc, 2000, p. 31). The appraisal theories of emotion were considered too â€Å"cognitive†, conscious, and slow, as appraisal often occurs unconsciously and quickly. The proponents of appraisal theories respond that appraisal does not need to be conscious as it often occurs unconsciously, automatically, and very quickly, and appraisal may be accompanied by subcortical as well as cortical processing (Ellsworth, Scherer, & Forgas, 2003). That’s why, according to appraisal theorists, although stressful experience is defined as a combination of appraisals, it is not experienced as such (Ellsworth, Scherer, & Forgas, 2003). However, this makes appraisal difficult to study. Self-reports might not adequately reflect one’s appraisal, and because appraisal is assessed a posteriori, a wide variety of confounding variables may interfere with accurate measurement. Within the biopsychosocial model of challenge and threat, appraisal is conceptualized as a process involving both unconscious and conscious processes; and therefore the best way to investigate appraisal would be to manipulate the task in the experiment, whereas subjective evaluations are considered much less reliable (Blascovich et al. , 2003). The biopsychosocial model is based on Dienstbier’s (1989) research. Dienstbier (1989) argued that there are two axes of stress response, sympathetic-adrenal-medullary (SAM) and hypothalamic-pituitary-adrenocortical (HPA), both of which serve to mobilize energy reserves. However, SAM activation involves the release of catecholamines, including epinephrine and norepinephrine, which have a half-life in the body for only a few minutes, whereas HPA activation involves the release of cortisol, which has a half-life in the body for approximately 90 minutes. Thus, SAM allows for rapid energy mobilization, whereas HPA involves long-term mobilization of energy resources. Dienstbier’s (1989) argued that fast large SAM response to the acute stressors coupled with low HPA response is indicative of the organism’s physiological toughness and adaptive pattern of stress responding. According to Frankenhauser (1983), SAM activation is associated with greater coping effort, whereas HPA activation reflects greater negative affect. Both Frankenhauser (1983) and Dienstbier (1989) believed that the stressors involving joint activation of the SAM and HPA have the most detrimental effect on health. For example, individuals with hypertension were found to have both higher diastolic blood pressure reactivity and higher cortisol reactivity to stress (Nyklicek, Bosch, & Amerongen, 2005). Thus, joint SAM axis and HPA axis activation is observed in hypertensive individuals, i. e. , the group that has traditionally been found to be especially vulnerable to the effect of stressful life events. Blascovich et al. (2003) argued that challenge reflects primarily SAM axis of stress response, whereas threat reflects joint activation of the SAM and HPA axes of stress response. Blascovich and colleagues did not empirically test this assumption. This conceptualization of the treat and challenge profiles as reflections of sympathetic/HP A reactivity has come under considerable criticism in the recent literature. Wright and Kirby (2003) argued that this conceptualization may not reflect the true activation of the stress response system, and it needs to be tested empirically before one can rely on the assumption. The Effect of Individual Differences on Hemodynamic Response to Stress Individual differences in hardiness may have impact on one’s response to stress. To understand the influence of individual differences on the physiological response to stress, it is important to establish if the hemodynamic profile is a characteristic if the individual, or a function of the situation. Would a specific situation elicit the same hemodynamic response in all individuals? Or, is the hemodynamic response a stable individual trait? To answer this question, one should consider the research on the consistency of hemodynamic profiles across diverse tasks and over time. Previous research suggested that hemodynamic responses are to some extent situation-specific. The myocardial hemodynamic profile is evoked by the tasks that require active coping (Obrist, 1983) or fight or flight response; whereas vascular hemodynamic response is evoked by the tasks that require passive endurance and offer little control, such as cold stressor tasks. Blascovich and colleagues (Mendes, Blascovich, Lickel, et al. , 2002) used a speech delivery task to validate their theory. The participants were instructed to deliver a speech in the presence of either a same-group partner (challenge) or an out-group partner (threat). As expected, the TPR response was higher in the threat condition, whereas CO response was higher in the challenge condition. Maier, Waldstein, and Synowski (2003) used a computerized mental arithmetic task to find that challenge appraisal was related to greater positive affect and task engagement, whereas threat appraisal was related to greater negative affect and perceived stress. Prkachin, Mills, and Husted (2001) found that anger-inducing interview led to the vascular response, whereas mental arithmetic led to the myocardial response. Hartley, Ginsburg, and Heffner (1999) showed their participants a previously recorded videotape, in which they were disclosing personal information about themselves. The participants in the active condition were allowed to mark the segments of the tape, which they wanted to re-shoot before the tape was â€Å"evaluated by the reviewer†; whereas the participants in the passive condition were not allowed to mark the segments of the tape. Both conditions produced similar elevation in blood pressure; however, in the active condition, blood pressure elevation was elicited through myocardial mechanism, whereas in the passive condition, blood pressure elevation was elicited through the vascular mechanism. Gregg, James, Matyas, and Thornsteinsson (1999) found that mental arithmetic task elicited myocardial response, and cold pressor task elicited vascular response. Quigley, Barrett, and Weinstein (2002) did a within-subject analysis of cardiovascular reactivity to the different tasks, and found that greater CO was associated with greater challenge implied by the task (serial subtraction); however, there was no difference in TPR. Although Quigley and colleagues (2002) investigated the differences in physiological reactions produced by different tasks within the individuals, they did not investigate the consistency of these reactions within the individuals themselves, i. e. , how stable was the hemodynamic response within a given person across different tasks. Previous research has established that at least some parameters of cardiovascular reactivity may be stable characteristic, such as blood pressure reactivity. In other words, the individuals with higher blood pressure reactivity would consistently exhibit this response pattern in different circumstances. Sherwood et al. (1999) argued that hemodynamic profiles also represent a trait, as individuals have a tendency to exhibit a certain type of response across diverse tasks. However, this is a very â€Å"relative† tendency as it is determined by comparison with other individuals. So instead of always responding in a fixed way to all situations, a particular individual would just show more/less myocardial/vascular response comparing to other individuals in the context of a given task. In addition, Sherwood et al. (1999) argued that the individual’s tendency to exhibit a particular hemodynamic response profile is stable over time. For example, middle-aged Type A men exhibited significant correlations over a 3-month interval on a competitive reaction time task (Sherwood et al. , 1999). Kamarck et al. (2000) identified myocardial and vascular responders in the initial testing session, and this tendency was stable after a 4-week interval. Thus, there is evidence that hemodynamic profiles may be relatively stable across tasks and across time, i. e. , some individuals may respond in a relatively more myocardial/vascular way to diverse tasks, and this response may tend to be stable over time. What are the factors that may influence one’s hemodynamic response pattern? Previous research indicated that ethnicity may be one of these factors as African American individuals typically have a tendency to respond in a vascular way; in addition, there are significant gender differences (Allen, Stoney, Owens, & Matthews, 1999). However, there is little research on the personality factors that might affect hemodynamic pattern of responding. Cooper and Waldstein (2004) found that hostility was associated with greater TPR. Cacioppo and colleagues (2002) and Hawkey, Burleson, Berntson, & Cacioppo (2003) found that in young adults, loneliness was associated with higher TPR and lower CO, whereas non-lonely young adults had higher CO. Tomaka and colleagues (Tomaka et al. , 1999) found that approach motivation was associated with higher CO. However, these two studies looked at the state variables, such as loneliness and approach/avoidance motivation. It might be of interest to investigate the effect of stable personality traits as well. Previous research has documented the health-enhancing and health compromising effect of a number of personality variables, such as optimism (Carver & Scheier, 2001), Type A, and hardiness (Maddi, 1999) in terms of blood pressure and future risk for hypertension and CVD development. Yet, there has been little research investigating the effect of personality variables on the hemodynamic mechanisms underlying BP reactivity. Blascovich and colleagues (2003) emphasized the need for research clarifying the effect of social and emotional factors on the patterns of physiological response associated with challenge and threat appraisals. HPA Reactivity in Response to Stress Situations Evoking HPA Activation HPA response is elicited by the situations implying significant threat to the individual, such as physical survival (Sapolsky et al. , 2000) and threat to one’s important goals (Carver & Scheier, 1999). Cortisol helps the organism manage short-term metabolic demands of the situation. Although cortisol response may be elicited by a variety of situations, it is the threat to one’s important goals that triggers this response. Dickerson and Kemeny (2004) conducted meta-analysis of 208 studies on cortisol reactivity. The effect size found in these studies varied from small (d=. 20) to fairly large (d=. 87) depending on the experimental task. The largest effect sizes were produced by tasks that involved uncontrollable threat to social self, such as public speaking, coupled with harassment, false feedback, perceived inability to complete the task, etc. (d = . 92). Thus, it appears that cortisol response to an acute laboratory stressor is most likely to be elicited by the uncontrollable social-evaluative tasks. These two features of uncontrollability and social evaluation have consistently been found to produce intense distress. Uncontrollability is one of the classical characteristics defining stressful situations. In a classical study, Glass and Singer (1973) showed that stress is associated with the situations involving uncontrollability and unpredictability. Social evaluation and self-presentation are common features of everyday life. In the experience of daily stress, interpersonal events play a central role, self-presentation is concerned with (1) one’s need to define one’s social self, and make one’s social self as close as possible to one’s ideal self; and (2) one’s need to please the audience (Baumeister, 1982). This need to make a favorable impression is very important for most people, and when they doubt that they succeed, people experience social anxiety marked by feelings of apprehension, self-consciousness, and distress. Social anxiety may be a dominant factor in modern life. Thus, an uncontrollable social-evaluative threat may produce intense experience of distress marked by significant cortisol elevation. The Relationship between Joint SAM and HPA axes Activation and Personality The research investigating joint HPA and SAM axes activation in response to stress indicated that a single manipulation of the experimental task may elicit different patterns of SAM and HP A response. For example, Earle, Linden, and Weinberg (1999) compared participants performing mental arithmetic task in front of an audience in harassment and no-harassment conditions. Harassment consisted of the scripted statements by same-gender experimenters. Both conditions produced sympathetic activation in terms of DBP (in men) and HR (in women), but it was the harassment condition only that produced significant cortisol elevation. The research on the relationship between joint HPA and SAM axes activation and personality dispositions during a single exposure to stress found a link between personality and SAM reactivity, but not between personality and HPA reactivity. This finding pertains to the studies involving single exposure to an acute laboratory stressor. For example, Taylor et al. (2003) found that high self-enhancers had lower sympathetic responses (SBP and HR), but authors did not find a significant difference in eortisol response to stress between the high and low self-enhancers. Gregg et al. (1999) did not find any meaningful correlations between eortisol and hemodynamic measures in the participants performing mental arithmetic task and cold pressor task. Schommer, Kudielka, Hellhammer, and Kirschbaum (1999) found no relationship between eortisol response to an acute laboratory stressor and the personality traits of Extraversion, Neuroticism, or Psychoticism measured with the Eysenck Personality Questionnaire-Revised. However, the research evidence with regard to the effect of exposure to repeated psychosocial stress did find a significant effect of personality on cortisol reactivity. Pruessner, Gaab, Hellhammer, Lintz, Schumer, and Kirschbaum (1999) exposed the participants to psychosocial stressor (public speaking) over a period of 5 consecutive days. Although during the first day, there was no significant relationship between personality factors (locus of control) and cortisol response, there was a significant relationship between locus of control and cortisol response later, from day two to day five. Pruessner et al. (1999) found that the combination of data obtained over the five consecutive days was necessary to detect the significant effect of personality traits, such as locus of control, on cortisol reactivity. In another study, Kirschbaum, Prussner, Stone, Federenko, Gaab, Lintz, Schommer, and Hellhammer (1999) investigated cortisol response to the repeated psychosocial stressor consisting of public speaking and mental arithmetic in a group of healthy young adults. The participants had been exposed to the stressor for 5 days. Kirschbaum and colleagues (1999) observed quick habituation of the HPA axis in some participants. These â€Å"low cortisol responders† exhibited large cortisol responses during the first day, and then this response subsided during the 5-day interval. However, in some participants, the HPA axis did not habituate to the stressor. These â€Å"high responders† kept producing large cortisol reactions throughout the entire 5-day period. The tendency to exhibit persistent high cortisol responses to repeated psychological stress was strongly associated with a number of personality variables, such as having lower self-esteem, viewing oneself as less attractive than others, and being more often in depressed mood, and lower extraversion. Cortisol high responders also reported significantly more symptoms of distress than cortisol low responders. In another study, Schommer, Hellhammer, and Kirschbaum (2003) also found a group of individuals with persistent cortisol response to psychosocial stress. In addition, high cortisol responders had significantly higher plasma ACTH levels. This study also looked at the sympathetic activation. The results suggested that SAM axis does not habituate to the repeated stress, as rapidly as the HPA axis does, because the levels of catecholamines (epinephrine and norepinephrine) were consistently elevated in both high and low cortisol responders. Pruessner et al. (1999) suggested that during the first exposure to stress, the effect of personality on HPA reactivity is masked by the novelty of the situation. Novelty, which is one of the classical features defining a stressful situation, has a profound effect on HPA reactivity masking moderating effect of personality. However, during the second and subsequent exposures to stress, the novelty is lessened, so the influence of personality dispositions may be investigated. Discussion and Conclusion According to the biopsychosocial model, challenge and threat response are evoked only by the situations involving â€Å"motivated performance† (Seery at al. , 2004). Engagement in the task is essential in eliciting both challenge and threat reactivity. The task should be â€Å"goal-relevant† (e. g. , it should be important for the participant). Hardiness, especially its commitment and control components, can be significantly correlated with conscientiousness, and both dispositions are associated with greater TPR increase in response to stress and little or no change in CO. Higher conscientiousness, commitment to the task and need to control the situation might lead to the greater engagement in the task and higher expectations for the quality of one’s performance. This might have resulted in greater negative affectivity about the task and about one’s performance. In contrast, the low-hardy participants can be probably disengaged, and, therefore, showed less reactivity. Due to the greater commitment to the task, high-hardy individuals showed a response profile that exaggerated the response typically evoked by the task. Thus, in a socially evaluative situation known to evoke a strong threat hemodynamic response profile, greater hardiness may be associated with greater threat response. This tendency may be due to the greater commitment to the task and greater need to control the situation. To fully understand the effect of hardiness on psychophysiology of human stress responding, the HPA reactivity should be evaluated (Seery et al. , 2004). Hardiness can be associated with a tendency towards exaggerated cardiovascular response to the psychosocial stressor. The general pattern of reactivity evoked by the TSST is consistent with the threat profile. It would be interesting to investigate reactivity to the stressor that evokes primarily challenge hemodynamic response profile. According to the biopsychosocial model, challenge and threat are defined by the ratio of the demand posed by the situation and perceived resources to cope with it (Blascovich et al. , 2003). Thus, in the challenging situation, the individuals would perceive more resources to cope with the demand. Due to the greater commitment to the task and greater conscientiousness, high-hardy individuals may potentially show greater challenge reactivity. However, it may also be possible that high-hardy individuals will still have greater concerns about their performance, which may be associated with greater distress reflected in a threat response profile. To sum up, it appears that in some individuals, the HPA axis cannot adapt quickly to the repeated stressful situation, so these individuals keep responding with high cortisol elevations consistently. 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