Potential pathways through which social relationships mediate cardiovascular reactivity during stress

The quality and quantity of one's relationships have been reliably linked to morbidity and mortality. More recently, studies have focused on links between relationships and cardiovascular reactivity as a physiological mechanism via the stressbuffering hypothesis. This hypothesis suggests that social support moderates or buffers the impact of stressful events. However, not all social relationships are consistently positive and hence associated with stress-buffering influences. To examine the more causal role of relationships on health we experimentally manipulated different relationship types (supportive, aversive, indifferent, and ambivalent) through the interpersonal behavior of an experimenter and examined this influence on cardiovascular reactivity. Although we were unable to create ambivalence, manipulation checks revealed expected significant experimenter main effects on ratings of helpfulness and upset. More important, we found an experimenter positivity main effect on systolic blood pressure reactivity, such that participants interacting with the high positivity experimenter had significantly lower systolic blood pressure. Unexpectedly, male participants interacting with a high negativity experimenter showed significantly lower diastolic blood pressure change. These findings indicate that relationships may be beneficial to one's cardiovascular health, but gender may influence motivational processes that impact on cardiovascular reactivity.

POTENTIAL PATHWAYS THROUGH WHICH SOCIAL RELATIONSHIPS MEDIATE CARDIOVASCULAR REACTIVITY DURING STRESS by Wendy Birmingham A thesis submitted to the faculty of The University of Utah in partial fulfillment of the requirements for the degree of Master of Science Department of Psychology The University of Utah May 2009 Copyright © Wendy Birmingham 2009 All Rights Reserved THE U N I V E R S I T Y OF UTAH G R A D U A T E SCHOOL APPROVAL of a thesis submitted by Wendy Birmingham This thesis has been read by each member of the following supervisory committee and by majority vote has been found to be satisfactory. Chair: Bert Uchino V/ 2 7 / o 9 V/ 2 7 / 0 I UNIVERSITY GRADUATE SCHOOL SUPERVISORY COMMITTEE APPROVAL THE U N I V E R S I T Y OF UTAH G R A D U A T E SCHOOL F I N A L R E A D I N G A P P R O V AL To the Graduate Council of the University of Utah: I have read the thesis of Wendy Birmingham in j t s fi n a i fo rm and have found that (1) its format, citations, and bibliographic style are consistent and acceptable; (2) its illustrative materials including figures, tables, and charts are in place; and (3) the final manuscript is satisfactory to the supervisory committee and is ready for submission to The Graduate School. Date Bert Uchino Chair: Supervisory Committee Approved for the Major Department Chair/Dean Approved for the Graduate Council David S. Chapn•ic f Dean of The Graduate School THE UN I V E R S] T Y 0 F UTA H G R A D U ATE S C H 0 0 L FINAL READING APPROVAL To the Graduate Council of the University of Utah: I have read the thesis of Wendy Birmingham in its final form acceptable; (2) its illustrative materials including figures, tables, and charts are in place; and (3) the final manuscript is satisfactory to the supervisory committee and is ready for submission to The Graduate School. Chair: Supervisory Committee Chapm ABSTRACT The quality and quantity of one's relationships have been reliably linked to morbidity and mortality. More recently, studies have focused on links between relationships and cardiovascular reactivity as a physiological mechanism via the stress-buffering hypothesis. This hypothesis suggests that social support moderates or buffers the impact of stressful events. However, not all social relationships are consistently positive and hence associated with stress-buffering influences. To examine the more causal role of relationships on health we experimentally manipulated different relationship types (supportive, aversive, indifferent, and ambivalent) through the interpersonal behavior of an experimenter and examined this influence on cardiovascular reactivity. Although we were unable to create ambivalence, manipulation checks revealed expected significant experimenter main effects on ratings of helpfulness and upset. More important, we found an experimenter positivity main effect on systolic blood pressure reactivity, such that participants interacting with the high positivity experimenter had significantly lower systolic blood pressure. Unexpectedly, male participants interacting with a high negativity experimenter showed significantly lower diastolic blood pressure change. These findings indicate that relationships may be beneficial to one's cardiovascular health, but gender may influence motivational processes that impact on cardiovascular reactivity. stress­buffering different interpersonal behavior of an experimenter and examined this influence on cardiovascular reactivity. Although we were unable to create ambivalence, manipulation checks revealed expected significant experimenter main effects on ratings of helpfulness and upset. More important, we found an experimenter positivity main effect on systolic blood pressure reactivity, such that participants interacting with the high positivity experimenter had significantly lower systolic blood pressure. Unexpectedly, male participants interacting with a high negativity experimenter showed significantly lower diastolic blood pressure change. These findings indicate that relationships may be beneficial to one's cardiovascular health, but gender may influence motivational processes that impact on cardiovascular reactivity. TABLE OF CONTENTS Page iv LIST OF FIGURES 1 8 8 Design 8 Procedure 8 Measures II Physiological Measures 11 Preliminary Analyses 14 Manipulation Check 14 Primary Analyses 15 Psychological Processes 15 Physiological Processes 16 Mediational Analyses 22 23 28 REFERENCES 30 TABLE OF Pag~ ABSTRACT .. . .. ...... . . . .. . . ........ .. ................ . .. . ....... .. .. .. . . .... . .. ... .. . .. .. .... .... IV LIST OF TABLES ........... ....... ... . .. .. . ........ .. ... .... .... . . ....... . ........ . ... ..... .. ..... vi .... . .. . ..................... . .... .. .. . ... ... .... ... .... .. . .. ..... .. . ........ ... vii INTRODUCTION ............................ . ................... ... ...... '" ....... . " ............ .. 1 METHOD ... .. .. .............. ........ ....... . ... ......................... . .. . ................ . ...... 8 Participants ............... '" ......... ... ............... ................ ......... . ....... .... 8 Design ......... ..... . .. .. . ..... . ... . . ......... . ........ . ... ... .. . ..... .. . .. .. .. .......... ..... 8 Procedure .. . ... .. ..... . ... .. .... . .... ........... .... . ..................... .. . . .. ..... .... .... 8 Measures ........................... .. .. .. ..... . ..... .. ... . .... . ..... .. ... . . ... . ... . ..... . . .. 11 Physiological Measures ...... . ... .................. . .......... . ........... .......... 11 Psychological Measures .. .. ............. . ................ . ............ . .... . ...... 12 RESULTS ............. .. ... .. . ................. . ... . ... ... . . ... ... .... . ..... ....... . ..... . .. .... .... 14 ....... . .. .... . ......... .. .... . ..... .. .. ...... ...... . ......... . . . .. .. Check. ..... ........................ ...... ...... ........ .. ... . . .. ... ..... . .......................... .................. . ..... . ........... ...... .................. . ....... . . .. . ... . .................. , .... . . ... . ... .... ...... . ... . ... . ... .. ... . .... .. .. .. .. ... .. .... ... ..... .. .. .... ........ ... ... .. .... . ............ . .. . ..... . .. DISCUSSION .. . ......... . .. ................................................. . ... . . ................ 23 Limitations ..... .. ...... ....... . . . . ... . ........................ ......... . . ......... . .. .. ...... 28 REFERENCES . . ....... . .... . ................................................. . ........... . .. . ...... 30 LIST OF TABLES Table Page 1. Least Squares Means of Manipulations 15 2. Least Squares Means of Psychological Measures 17 3. Least Squares Means Dependant Variables 18 ................................................... .. . ...... ... . ............. .... ........ . ... .......... . . .. .... .. ....................... LIST OF FIGURES Figure Page 1. General conceptual framework incorporating the positive and negative aspects of social relationships 2 2. Systolic blood pressure epoch x positive condition 20 3. Diastolic blood pressure negativity x epoch 20 4. Diastolic blood pressure negativity x gender 21 5. Parasympathetic withdrawal 21 and negative aspects of social relationships . ........ . .................................... .2 2. Systolic blood pressure epoch x positive condition .... .. .............................. 20 3. Diastolic blood pressure negativity x epoch ........... . .......... ......... .. ... .. .. ... .. 20 4. Diastolic blood pressure negativity x gender. .............................. . .... .. .. ..... 21 5. Parasympathetic withdrawal .... .. .. ................ ................ .... .......... . ...... .. 21 INTRODUCTION Epidemiological research indicates that social relationships may protect individuals from various causes of morbidity and mortality, including cardiovascular disease which is the leading cause of death in the U.S. (Berkman, 1995; Cobb, 1976; Cohen, 1988; House, Landis, & Umberson, 1988; Uchino, 2004). For instance, a review by House et al. (1988) found evidence suggesting that the link between social relationships and health was comparable to risk factors such as smoking and lack of physical activity. Most of this research has focused on the protective benefits of supportive social relationships. However, not all social relationships are consistently positive. Although social relationships can be sources of support and understanding, they can also be sources of conflict, criticism, jealousy, and rejection (Braiker & Kelley, 1979; Major, Zubek, Cooper, & Cozzarelli, 1997; Robles & Kiecolt-Glaser, 2003; Smith, Gallo, & Ruiz, 2003). Prior research on social support has tended to ignore the complexity of relationships that may include both positive and negative aspects. A more comprehensive model of such relationship influences is depicted in Figure 1. & & & KiecoIt-& Ruiz, 2003). Prior research on social support has tended to ignore the complexity of relationships that may include both positive and negative aspects. A more comprehensive model of such relationship influences is depicted in Figure 1. High Ayersive Network Tie Ambivalent Network Tie NEGATIVITY Indifferent Qfefwork Tie Supportive NetworkTie Low Low * High POSITIVITY Figure 1. General conceptual framework incorporating the positive and negative aspects of social relationships. According to our model, social network members that are mostly sources of positivity would represent the high positivity / low negativity corner (e.g., a loving spouse or friend that you can always count on). Network ties that are mostly sources of negativity would represent low positivity / high negativity (e.g., an unreasonable supervisor). Those low in both positivity and low negativity are labeled as indifferent and may represent network ties that are characterized by low levels of social interactions (a neighbor you rarely see, a student in a class with you). A relatively unique aspect of this model for the social relationships and health literature is represented in the high positivity / high negativity corner or what we label an ambivalent relationship member. This refers to network members that are a relatively strong source of both positivity and negativity (e.g., overbearing but also caring parent). ..... Aversive N eh\ro.t:.k .... ..• ~ ... ..... ....... Indjffe·~ent .~e6vork ...... ........ ..... ... ... ......... .. ... ...... ~: ...... . ........ ....... ... . .... .... ..• .. Ambival..~r"t N etw.of'k. ....... ............ . ..... . Suppot:tive NetworkT!e ..... 2 I I indifferent I There are several reasons why a study of ambivalent relationships, separate from supportive and aversive relationships, may be important: Whereas supportive ties reduce cardiovascular reactivity, ambivalent ties predict worse mental health outcomes such as depression, perceived stress, and lower satisfaction with life (Uchino et al. 2001; Uchino et al., 2004). Studies have also shown that interactions with ambivalent friends increase (a) cardiovascular reactivity during laboratory stress, (b) cardiovascular reactivity during support-seeking, and (c) ambulatory blood pressure during daily life (Holt-Lunstad, Uchino, Smith, & Hicks, in press; Holt-Lunstad et al., 2003; Uno, Uchino, & Smith, 2002). Thus, a relationship characterized as ambivalent may lead to significant interpersonal stress above and beyond that of aversive ties. This may occur because if a relationship is primarily a source of negativity, one may habituate to the aversive relationship by using specific coping strategies such as avoidance or discounting. However, an ambivalent network tie that is a source of both positivity and negativity may be considerably less predictable and thus may be associated with greater emotional responses, and, therefore, reactivity. Thus, one aim of this study is to replicate our prior research showing that ambivalent ties are associated with greater cardiovascular reactivity compared to other network types. A second and primary aim of this study is to investigate the physiological and psychological pathways potentially associated with different relationship types. At the biological level, cardiovascular reactivity is the physiological manifestation of stress, and studies have demonstrated the link between cardiovascular reactivity and heart disease (Manuck, 1994; Trieber et al., 2003). For instance, cardiovascular reactivity has been found to predict (a) sustained hypertension (Borghi, 1986), (b) blood pressure levels in 3 ai. aI., aI., ofthis aI., 4 young adults 10 to 15 years after reactivity assessments (Light, 1992), and (c) blood pressure rises in children over a five year period (Murphy, 1992). Reactivity has also been found to be a factor in coronary heart disease, atherosclerosis, and greater left ventricular mass (Manuck, 1994). Thus, relationships may be related to health outcomes by decreasing (i.e., supportive ties) or increasing (ambivalent ties) cardiovascular reactivity. Most of the literature on relationships and reactivity as a physiological mechanism has examined the stress-buffering influences of social support which suggests that social support buffers the impact of stressful events (Cohen, 1985; Kiecolt-Glaser, 1984). Consistent with this perspective, Gerin et al. (1995) found that social support (supportive vs. neutral confederate) was associated with significantly lower blood pressure and heart rate during a debate stressor. Similarly, Lepore, Allen and Evans (1993) found men and women had smaller increases in blood pressure when they gave stressful speeches in the presence of a supportive other than when they gave the speech alone or in the presence of a nonsupportive other. These studies support the assumption that the presence of a supportive other can reduce physiological response to a stressor, although there is mixed evidence on whether a stranger provides the same level of stress buffering effects as a friend (Christenfeld, 1997; Edens, 1992; Glynn, 1999; Kamarck, 1995). In addition, whereas Lepore (1993) notes that the mere presence of a stranger may increase reactivity, Fontana et al. (1999) found that the buffering effects of social support can be obtained without the supporter being familiar to the receiver of the support. Overall, however, social support appears to be generally related to lower cardiovascular reactivity during stress (Thorenstein et.al., 1999) 5 Whereas existing literature tells us that social support and reactivity are linked and the association between reactivity and health outcomes appears to be particularly strong for cardiovascular disease, little is presently known about the psychological mechanisms linking relationships to CVR. It has been suggested that social support may reduce stress by altering appraisal of the stressor, by changing coping patterns, or by affecting self-perceptions such as self-esteem, or enhancing self-efficacy (Barrera, 2000; Cohen, 1985). However, prior studies in the broader social support and health literature have not yet directly elucidated such potential psychological pathways (House, 2001; Uchino, 2004). Studies linking social support to lowered cardiovascular reactivity have also provided little evidence for the psychological mechanisms responsible for such links (Gerin, 1992; Kamarck, 1990, 1995, Lepore, 1998; Lepore et al., 1993; Tomaka, 1997). For instance, Gerin's work supporting the likelihood of social support promoting certain types of coping behaviors that could moderate reactivity to the support condition, also found the self-report measures of stress and anxiety did not differentiate support conditions. However, in the Smith et al. (2004) study of mental activation of support in the laboratory, participants in the supportive tie condition tended to report smaller increases in state anxiety during the speech stressor than did those in the acquaintance condition. mediational analysis, when changes in state anxiety were statistically controlled, the significant results of the support manipulation on each of the physiological responses were rendered nonsignificant; thus there was some evidence that the supportive tie manipulation reduced cardiovascular reactivity during the speech stressor through psychological aI., aI. In 6 reduced state anxiety. However, most studies have not found evidence for such psychological pathways. summary, the link between social relationships and heath outcomes is well-documented, but there is still the unanswered question concerning the pathways through which reactivity of the cardiovascular system is mediated by social support. In the present study, we address these issues in several ways. First, we use direct manipulation of the relationship in a more controlled manner. most studies, relationship quality is examined by bringing in a friend. However, a more controlled approach would be to directly manipulate relationship quality and then observe its influence on the psychological mechanisms and cardiovascular assessments. This more controlled context may increase the sensitivity of the experiment to direct mediational influences by directly activating psychological processes such as appraisals and state anxiety. At the least, it would involve replication of prior literature using a different operationalization of relationship quality. A second feature that will address the issues raised above involves the use of more comprehensive measures of psychological processes, especially appraisals that may be linked to distinct patterns of physiological reactivity. Tomaka and colleagues (1997) demonstrated that threat and challenge cognitive appraisal were associated with different physiological response patterns. For instance, threat elicited moderate cardiac activation coupled with increased systemic resistance, while challenge elicited higher cardiac activation with a decrease in systemic resistance. The current study will include measures of appraisal to take advantage of its links to more complicated physiological profiles. In well­documented, In different Replicating prior research we expect that a supportive experimenter will be associated with the lowest cardiovascular reactivity. We predict that physiologically the ambivalent experimenter will elicit greater cardiovascular responses from baseline than the aversive experimenter. In addition we predict that the aversive experimenter will elicit greater cardiovascular responses from baseline than the indifferent and supportive experimenters. Furthermore, the ambivalent experimenter should elicit higher perceived threat and state anxiety, as well as lower perceived control. These psychological mechanisms should mediate the links between relationships and cardiovascular reactivity. 7 METHOD Participants Participants were 77 healthy men and 101 healthy women with a mean age of 23.5 and an age range of 18-57. Participants were mostly White (75%) and 79% reported being single with some college education. Participants were recruited either from an introductory psychology course, compensated with extra credit, or from the community and paid for their time. Because physiological measurements were assessed, participants were excluded who were not generally healthy, or had medical conditions with a cardiovascular component (e.g., no hypertension, see Cacioppo et al., 1995). Design The design was a 2 (Positivity: low, high) X 2 (Negativity: low, high) X 3 (Epoch: Preparation, speech, recovery) mixed model design with relationship positivity and negativity as between-participant factors and epoch was a within-participant factor. Procedure Upon arrival to the study, participants were randomly assigned to a relationship positivity and negativity condition. Experimenter One then obtained informed consent from each participant. The consent form contains information on the nature of the study, potential risks, potential benefits, and confidentiality. Experimenter One then positioned .'~ aI., a properly sized cuff on the nondominant upper arm of the participant. We used the Dinamap 100 Blood Pressure Monitor to obtain cardiovascular assessments including systolic and diastolic blood pressure (SBP, DBP), heart rate (HR) and mean arterial pressure (MAP). Additionally, because blood pressure is a function of changes in cardiac output (CO) and total peripheral resistance (TPR), Experimenter One attached disposable electrodes to the participant according to published guidelines (Sherwood, Allen, Fahrenberg, Kelsey, Lovallo, & van Doornen, 1990) in order to obtain measures of HR, CO and TPR using a Mindware Impedance Cardiograph. Participants were then given psychological and demographic questionnaires to complete after which a 10-minute baseline reading was obtained with readings of SBP, DBP, HR and MAP taken once every 90 seconds after the first 5 minute period. After the baseline reading, participants were given pre-task appraisals by Experimenter One as well as perceived control and state anxiety questionnaires. Participants were then asked by Experimenter One to imagine that they are shopping in a store when a security guard falsely accuses them of shoplifting. Participants were told they would be given 3 minutes to prepare a statement that would be given to the store manager stating their side of the story, what the security guard did wrong, how they can prove they did not steal and what should be done with the security guard who has made this false accusation. They were then told they would have 3 minutes to present their speech. Experimenter One then turned them over to Experimenter Two, whom they were told was in the control room monitoring their vital signs and listening to, and evaluating their speech. In order to manipulate the interaction with Experimenter Two, recorded 9 Doomen, ofHR, ofSBP, 10 versions of the directions for the speech task were delivered via the intercom system and are described below: Supportive (high positivity, low negativity) relationship: "I'll be just inside this room while you perform your speech. You will need to put together an organized and knowledgeable speech. However, if you need me for any reason or if you have any questions, don't hesitate to ask me. I appreciate your participation in this experiment, and I'd like to be helpful if you should need any help." Aversive (low positivity, high negativity) relationship: "I'll be just inside this room while you perform your speech. Now - if you were listening a moment ago you know you need to put together an organized and knowledgeable speech you can. If for some reason you need me because you are failing to do the task right, let me know and I will try to help you do better." Ambivalent (high positivity, high negativity) relationship: "I'll be just inside this room while you perform your speech. Now - if you were listening a moment ago you know you need to put together an organized and knowledgeable speech you can. However, if you need me for any reason or if you have any questions, don't hesitate to ask me. I appreciate your participation in this experiment and like to be helpful. So if for some reason you need me because you are failing to do the task right, let me know and / will try to help you do better.'''' Indifferent (low positivity, low negativity) relationship: "I'll be just inside this room while you perform your speech. You need to put together an organized and knowledgeable speech." if better." if I'd jailing I better." 11 During both the preparation stage and the speech-task stage cardiovascular measures were taken every 90 seconds after an initial 30-second period. All cardiovascular measures were averaged across minutes to increase reliability. After the stressor task, participants were given assessments by Experimenter One of perceived control and state anxiety. In order to verify the Experimenter Two/participant relationship, participants were asked to rate how helpful and how upsetting they felt about the experimenter generally on a 1 {not at all) to 6 {extremely) point scale. A criterion measure of subjectively felt ambivalence was also assessed by asking participants how mixed or conflicted they felt towards experimenter 2 (Priester & Petty, 1996). Following these questionnaires, the blood pressure cuff and impedance electrodes were removed from the participants and they were debriefed and thanked for their participation. Measures Physiological Measures Cardiovascular assessments. A Mindware 2000D Impedance Cardiograph was used to measures ECG, basal thoracic impedance (ZQ), and the first derivative of the impedance signal (dZ/dt). Disposable spot electrodes were placed according to published guidelines (Sherwood et al., 1990). The impedance data were collected and ensemble averaged within 1-minute epochs. Each ensemble-averaged waveform was verified or edited prior to analysis. All physiological measures were averaged within epochs (baseline, preparation, task and recovery) to increase the reliability of our assessments (Karmarck, 1992). Cardiac output and total peripheral resistance was scored following ((ZO), aI., I-12 standard procedures (Sherwood et al., 1990) and averaged across minutes to increase reliability (e.g., Kamarck et al., 1992). A Dinamap Model 100 monitor was used to measure SBP, DBP, and HR. The Dinamap uses the occillometric method to calculate blood pressure. Cardiovascular assessments were obtained via a properly sized occluding cuff positioned on the nondominant upper arm. Mean SBP, DBP, and heart rate were calculated by averaging across each assessment period (i.e., baseline, preparation, speech) to increase reliability (Kamarck et al., 1992). Psychological Measures Social Relationships Index (SRI). The SRI was initially developed as a self-report version of the social support interview (Kiecolt-Glaser et al., 1991; Pagel et al., 1987; Uchino, Kiecolt-Glaser, & Cacioppo, 1992). Participants rated how helpful and how upsetting the experimenter generally was on a 1 (not at all) to 6 (extremely) point scale. A criterion measure of subjectively felt ambivalence was also utilized by asking participants how mix/conflicted they felt towards the experimenter (Priester & Petty, 1996). Prior studies suggest that the SRI is psychometrically sound, with good internal consistency and test-retest reliability (Campo et al., in press). Threat and challenge appraisals. Prior to the speech task, participants completed a measure of challenge and threat appraisals utilized by Tomaka et al. (1997). Participants were asked to rate on a 6-point Likert scale "how threatening do you expect the task to be" and "how able they were to cope" with the experiment using a 1 to 6 point Likert scale with 1 = Not at all and 6 = Very Much. aI., aI., Modell 00 a.aI., self­report aI., aI., aI., a1. Much. al., - Low = High. al., & (not at all) (very much) alpha > IMP. al., IPC) specifically & has been demonstrated to have adequate psychometric properties. 13 Perceived control. Perceptions of perceived control were assessed via items used in prior social psychophysiological studies (Gerin et aI., 1995). Participants were asked to rate the amount of control they perceived they had over the evaluation of their speech task on a one to ten point Likert scale with 1 "'" and 10 "'" This measure has been shown to be sensitive to experimental manipulations of control (Gerin et aI., 1995). State anxiety scale. The short-form of the Spielberger State-Trait Anxiety Scale was administered to participants both before and following the psychological stressor (Marteau Bekker, 1992). Participants were asked to rate their current feelings on a 1 to 4 point scale. The internal consistency of the scale in prior work has been high (Cronbach's alpha> .78). Impact Message Inventory, Form II (1M!). The IMI (Kiesler et aI., 1985) is a circumplex-based inventory designed to evaluate perceptions of another's interpersonal behavior, along the dimensions of the interpersonal circumplex (lPC) - specifically friendliness versus hostility and dominance versus submissiveness. Previous research has established the relevance of the IPC in the conceptualization and measurement of social support (Trobst, 2000). The IMI contains 32 items with 4 items per octant. Evidence supports the circumplex structure of the IMI (Kiesler, Schmidt, Wagner, 1997) and it the relationship manipulation as assessed by the Social Relationship Index (Uchino et al., 2001) using a 2 (Positivity: low, high) X 2 (Negativity: low, high) X 2 (gender: male, female) ANOVA to determine if there were differences between the positive and negative condition or any interaction of positivity and negativity resulting in an ambivalent relationship. No interaction of positivity and negativity was obtained, suggesting failure to manipulate ambivalence in the current study. However, the analysis revealed a main effect for positivity such that those participants found the experimenter to be more helpful (A/low = 3.50, Mhlgh = 4.16), ( F ( l , 164) = 6.76,/? = .01, eta-squared = .036) as positivity increased. Moreover a negativity main effect showed participants found the experimenter more upsetting (M]ov/= 1.26, Mh jgh= 1.98), ( F ( l , 164) = 20.47,/? < .0001, eta-squared = . 106) as negativity increased. Additionally, examination of mixed and conflicted feelings also revealed a main effect such that those participants in the high negative condition also experienced more mixed and conflicted feelings toward the experimenter ( M i o w = 1-50, Mhigh^ 2.35), ( F ( l , 163) = 17.36,/? < .0001, eta-squared = .095). These results suggest that there were significant differences in the manipulated relationships between the experimenter and the participant (see Table 1). .' " RESULTS Preliminary Analyses Manipulation Check To verify the relationship classification, we first examined the characteristics of aI., (M1ow= Miligh (1, 6.76,p (Miow = Mhigh = (F (1, 20A 7, P < = .1 06) and (Miow = 1.50, i\1high = (1, = 17.36, P = relationships between the experimenter and the participant (see Table 1). examined ANOVA. Mm e n = 1.64, M w o m e n = 2.32), ( l , 166)= p = .0003, eta-squared = .074), such that examining levels of perceived control, a main effect for gender ( M m e n 6.49, M w o m e n = F ( l , p less control over the task than men. negative experimenter condition perceived the task as more threatening (F(\, 166) 5.10,p = = found Manipulations Women Men Measure ^o w P°s^ive Low High Low High Low High Low High Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. SRI Positive 3.62 2.89 4.387 3.5 4.352 3.13 4.88 3.85 SRI Negative 1.29 2.38 1.32 2.06 1.35 1.93 1.06 1.52 SRI 1.6 2.68 1.58 2.313 1.47 2.3 1.36 2.074 15 Table 1 Least Squares Means of Manipulations Measure Low Positive High Positive Low Positive High Positive l.06 Mixed Primary Analyses Psychological Processes To examine potential pathways linking relationships to health, we next examined psychological processes before and during the stressful speech task by conducting a 2 (Positivity: low, high) X 2 (Negativity: low, high) X 2 (gender: male, female) ANOV A. We examined levels of perceived threat and found a significant main effect for gender (Mmen Mwomen = ( F 1, 166) = 13.9, women felt more threatened by the task than men. Consistent with this finding, when Mmen = Mwomcn = 5.37), ( F(1, 166) = 6.66,= .01, eta-squared = .037), was found such that women felt A gender by negativity interaction was also found such that women in the high F (1, = p = .02, eta-squared = .027), whereas no negative condition differences were found dominant (Mmen= -0.37, M w o m e n = 0.09), ( F ( l , 1 6 6 ) = l 1.07,/? .001, eta-squared = .056) Another gender main effect ( M m e n = 1.40, M w o m e n = 0.32), (F (1,166)=11.55,/? .001, eta-squared affiliation high negativity experimenter was viewed as more dominant (M\ow = -.043, Mhigh = 0.15), ( F ( l , 1 6 6 ) = 16.85,/? < .001, eta-squared = .085), and less friendly ( M | 0 W = 1.75, Mhigh = -0.03), ( F ( l , 1 6 6 ) = 30.92,/? < .001, eta-squared = .136 [see Table 2]). Additionally, main effects were found for affiliation in both the positive and negative conditions such that in the high positive condition (F (1, 166) = 15.66,/? = .0001) participants felt greater affiliation with the experimenter and in the high negative condition ( F ( l , 166) = 29.49,/? .0001) participants felt less affiliation with the experimenter. No other effects were significant. female) for men. Overall, these results suggest that women may have been more sensitive to aspects of the relationship manipulation than men. 16 The Impact Message Inventory (IMI) was also completed by the participants in order to determine differences in perceived levels of dominance and affiliation with the experimenter. A gender main effect showed women viewed the experimenter as more Mmen = Mwomen (1 ,166)=11.07,p < Mmen Mwomen 11.55, p < eta­squared = .051) revealed women felt less af1iliation with the experimenter than men felt. A significant negative condition main effect on dominance was also found such that the Mow F(1,166) 16.85,p Mow Mhigh= F(1,166) 30.92,p 15.66, p greater (1, 29.49,p < Physiological Processes A 2 (Positivity: low, high) X 2 (Negativity: low, high) X 2 (Gender: male, female) X 3 (Epoch: preparation, task, recovery) mixed model ANOVA was conducted on the cardiovascular change scores (i.e., task minus baseline). The major physiological dependent measures included systolic blood pressure (SBP), diastolic blood pressure Note. al., equipment failure. Participants with missing data were eliminated from the analysis and the degrees of freedom were adjusted accordingly. Baseline scores for each respective (F = 4.09, p = .02). Follow up analysis within epochs revealed a significant positivity main effect for the task period (F (1,163) = 4.51,/? = .03, eta-squared = .023) only such that Least Squares Means of Psychological Measures 17 Table 2 Measures Women Men Measures Low Positive High Positive Low Positive High Positive Low High Low High Low High Low High Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Threat 1.91 2.32 2.23 2.82 1.82 1.36 1.78 1.60 Coping 5.17 5.36 4.94 4.94 4.56 5.36 5.00 5.28 State Anxiety .30 .36 .16 .35 .23 .17 .06 .28 Anger .11 .20 .10 .14 .18 .13 .02 .07 Affiliation .85 -1.29 1.97 -.27 1.08 .23 3.09 1.21 Dominance -.17 .68 -.32 .19 -.59 -.16 -.63 -.11 Neg. = Negative (DBP) and heart rate (HR), as these measurements have been reliably linked to health outcomes (Treiber et aI., 2003). Additionally, impedance derived measures of cardiac output (CO) total peripheral resistance (TPR), pre-ejection period (PEP) and RSA were examined. Missing values arose on some measures due to experimenter error or measure were statistically controlled in the analyses. See Table 3 for least squares means. Analysis for blood pressure revealed a positivity by epoch interaction on SBP (4.51, P Women High Positive Low Positive Measures SBP Prep 10.86 11.07 9.10 13.83 12.51 9.60 8.31 9.83 SBP Task 24.46 21.74 20.60 21.54 26.80 25.58 21.50 17.75 SBP Rec 3.91 4.49 4.13 4.57 5.64 5.11 4.09 4.71 DBP Prep 6.18 6.65 6.47 7.41 7.14 3.34 6.44 6.69 DBP Task 13.19 13.19 13.90 12.59 16.18 10.65 14.16 11.57 DBP Rec . .33 2.41 2.08 1.39 2.65 -1.39 .97 2.11 HR Prep 9.48 11.29 8.98 10.02 12.57 12.87 9.96 10.67 HR Task 18.69 16.12 16.31 19.46 16.55 17.06 15.14 15.08 HR Rec 1.31 1.38 .69 .80 1.74 2.42 1.33 3.31 CO Prep .80 .18 -.07 1.44 .11 -.06 -.56 -.002 CO Task .67 .74 .38 1.35 1.07 1.25 .14 1.11 CO Rec -.09 .17 .102 .66 -.50 .08 -.86 -.08 PEP Prep -5.39 -7.26 -4.59 -6.74 -14.05 -10.86 -7.72 -7.54 PEP Task - 10.02 -5.71 -7.01 -9.14 -12.52 -10.59 -7.44 -7.35 PEP Rec . -.44 -2.00 - 1.63 -.87 -4.34 -6.97 -3.06 -2.86 TRP Prep 241.39 94.02 76.91 -17.22 -80.18 187.26 226.16 170.26 TRP Task 131.25 57.55 59.12 -28.57 -26.34 -34.25 83.76 -35.67 TPR Rec 209.03 53.64 1.08 -4.95 193.09 22.08 166.87 10.79 RSA Prep -.27 -.41 -.47 -.15 -.33 -.44 -.05 -.26 RSA Task -.41 .37 -.73 -.33 -.35 -.04 -.36 -.09 RSA Rec 38.48 38.42 40.27 41.03 41.27 38.79 35.81 37.86 Least Squares Means Dependant Variables 18 Table 3 Dep endant Variables Men . High Positive Low Positive Low High Low High Low High Low High Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Ree 4.7] 13. 19 ]2.59 16.] 8 Ree 15 .08 HRRee l.74 3.3 1 CORee 7 .54 Ree 3 .06 Ree 53 .64 l.08 193 .09 Ree 4l.03 found. F=3.9,p into (F(\, 5 . 0 1 , p (F = 4.30, p significant decrease in diastolic blood pressure (F (1, 163) = 5.60,p = .02) as experimenter negativity increased (see Figure 4). We next examined heart rate and found an epoch by gender interaction (F = 2.98, p = .05) such that women had lower heart reactivity than men. These findings were mostly due to faster heart rate reactivity during the recovery period for women than for men (F = 3.34, p = .06). of data during the editing process (TPR total n 135, CO total n 140). We then examined sympathetic nervous system (SNS) and parasympathetic nervous system (PNS) influence on the heart in a more exploratory fashion given the lack of effects on heart rate. Analysis revealed an epoch by negativity interaction on RSA (F = 2.97, p = .05). Consistent with the DBP effect, there was less parasympathetic withdrawal during the task epoch as negativity increased (see Figure 5). No other effects were found to be significant. systolic blood pressure significantly lowered as experimenter positivity increased (see Figure 2). No other effects on systolic blood pressure were found. 19 Analysis also revealed a negativity by epoch interaction (F = 3.9, p = .05) on diastolic blood pressure. As shown in Figure 3, further analysis into this effect revealed a significant negativity main effect within the task period F (1, 163) = 5.01,= .02) only such that diastolic blood pressure decreased as experimenter negativity increased. This main effect was qualified by a negativity by gender interaction (1,163) < .05, eta-squared = .023) such that men, but not women experienced an unexpected significant 1,163) p = We then analyzed the underlying determinants of blood pressure by using impedance derived measures of CO and TPR. However, our analysis found no significant effects on CO or TPR. It is important to note that we lost a significant amount = = F= 20 Changes mmHg n • Prep Task Recovery Figure 2. Systolic blood pressure epoch X positive condition mmHg Prep Task Recovery Figure 3. Diastolic blood pressure negativity X epoch 25 20 15 10 5 o ~--- 16 14 12 10 Change in 8 6 4 2 0 D Low Pos High Pos OLowNeg High Neg 21 Log Units 0 -0.2 -0.3 -0.4 -M l / ... •Low Neg •High Neg Prep Task Figure 5. Parasympathetic withdrawal Recovery Change mmHg Men Women Figure 4. Diastolic blood pressure negativity X gender 0.1 -0.1 Log Units -0.2 -0.5~---"'----"'---~r' o Low Neg High Neg DLow High 22 Mediational Analyses We also conducted mediational analyses of the psychological pathways that demonstrated significant main effects of positivity or negativity (or an interaction with gender). However, in all cases the criteria for mediation were not established (i.e., either mediator was not related to the physiological outcomes, or did not decrease a previously significant association). us than other network ties and (b) to investigate the physiological and psychological different al., al., tie was related to lower cardiovascular reactivity during stressful times. These findings are consistent with the stress-buffering influences of social support in that the impact of a stressful event can be buffered by the influence of network ties in our social support system (Cohen, 1985; Kiecolt-Glaser, 1984). However, we found little direct evidence for the psychological mechanisms responsible for this stress-buffering influence or the hypothesis that ambivalent ties would be associated with increased cardiovascular reactivity. al., because an ambivalent or indifferent tie may be viewed in a more positive light simply because they came to assist the participant with the study, thereby producing a transient DISCUSSION The primary aims of this study were (a) to replicate findings indicating that ambivalent relationships network ties are psychologically and physiologically worse for pathways potentially associated with different relationship types. In comparison to prior work, we pursued these aims using experimental manipulations of several different relationship types (Gerin et aI., 1992; Lepore et aI., 1993). Overall, a socially supportive findings reacti vi ty . Although several researchers have found that the presence of a supportive other can reduce blood pressure response to a stressful task, there is mixed evidence still on whether a stranger can provide a stress-buffering influence (Christenfeld et aI., 1997; Edens, 1992; Glynn, 1999; Kamarck, 1995). Prior work on friendships may be limited ambivalence was less successful. In order for a relationship to be considered ambivalent positivity negativity. more mixed and conflicted about the experimenter as negativity increased, there was no evidence that our attempt at manipulating relative ambivalence with an experimenter was successful. rich al., 24 shift toward a supportive friend. We therefore attempted to manipulate the relationship between a stranger (i.e., experimenter) and the participant in a more controlled manner in order to create four relationship type that differed in their positive and negative substrates: supportive, aversive, indifferent and ambivalent. Our manipulation checks showed participants found the experimenter to be much more helpful as positivity increased and more upsetting as negativity increased. However, our attempt to create it must contain aspects of both and And whereas participants felt Our failure to create ambivalence in the laboratory may simply be that ambivalence can only be established over the length of more established relationships. The mere definition of ambivalence lends itself to a more time-rich environment: one must have enough interactions with the network member to become familiar with their good points and bad points and then be motivated enough by the good points to remain in the relationship (Kelley, 1983b). Additionally, an ambivalent network member is considered to be less predictable (Uchino et aI., 2001) than a supportive or aversive network member and unpredictability may also be a characteristic of the relationship which must be established through multiple interactions. Furthermore, an individual may need to feel a "closeness" with the network member (as opposed to a stranger in the laboratory) as the individual likely has a vested interest in maintaining the relationship despite its negativity, a condition not easily replicable in a laboratory situation. It self-impactful. ambivalence in a stranger it may not result in the same degree of interpersonal stress given this lack of overlap. This is an important question for future work to see if this social-cognitive process is an important mediator of links between ambivalence in existing relationships and increased cardiovascular reactivity. findings with the positive experimenter. This is consistent with prior research but also adds to the social support model: even strangers can provide support. Of course, it is likely that a supportive friend may provide the most effective support given their prior supportive history (Christenfeld et al., 1997), but simply receiving support without that relationship history appears sufficient to lower stress responses. further 25 The Self-Expansion Model (Aron & Aron, 1996) framework views relationship closeness (or interconnectedness) as a mental representation of how an individual views himself (his traits, feelings, characteristics, etc.) when he is with certain "others". Some relationships have very little overlap between the concept of "self' and the concept of "other," whereas other relationships contain a great deal of overlap. may be the case that the nature of ambivalent relationships may require an overlap between self-other representation for it be impactfuI. Thus, even if we were able to manipulate state-like oflinks Whereas our lack of ability to create ambivalence may indicate that laboratory studies may not be able to effectively create ambivalence with strangers, our findings indicate that strangers can still effectively provide support. Participants found the experimenter more helpful as experimenter positivity increased, and systolic blood pressure was significantly lower during the speech task if the participant was interacting aI., Consistent with current literature (Kiecolt-Glaser & Newton, 2001), we further observed that gender played a role in how the experimenter was perceived. Whereas both 26 affiliation over the evaluation of the task, but they also felt more threatened by the task as experimenter negativity increased. These findings seem to indicate that women were more psychologically reactive to the relationship context than men. This may be because women think more about their relationships and think with greater complexity regarding those relationships, than men do (Acitelli & Young, 1996). Women are socialized early to relationship awareness. Indeed, some researchers suggest that women's self-concept is more relational than men's self-concepts (Markus & Oyserman, 1989); that is, they tend to use relationships in order to define themselves relative to individual, personal characteristics. Additionally, women may experience trouble in relationships as more stressful than men (Davis et al., 1999). Unlike prior work, we did not find these differences to be mirrored in physiological reactivity. This could be due to differences in the use of strangers versus established relationships which may be a weaker manipulation (Kiecolt-Glaser & Newton, 2001). experimenter. men and women felt more affiliation with the positive experimenter and less affiliation with the negative experimenter, women felt significantly less affiliation with the experimenter than the men. Women also found the negative experimenter to be significantly more dominant. Additionally, women not only felt they had less control aI., Unexpectedly, we found that diastolic blood pressure, especially in men, decreased as experimenter negativity increased. In addition, there was less parasympathetic withdrawal as negativity increased. One possible explanation for this pattern could be related to a withdrawal of effort in response to a negative experimenter. Having to interact with someone that is acting in an aversive manner may lead people to simply withdraw from the interaction. In our contrived interaction the participant was have been emotional or psychological. Marital studies show that when men are in situations of conflict, they may withdraw from the conflict rather than engage (Christensen & Heavey, 1990). Christensen and Heavey postulated a demand-with-withdrawal pattern, which was supportive of both a gender and a social structural paradigm. The social structural paradigm asserts (as noted above) that women view relationships differently than men, with women's identity developed within the context of their relationships. The gender paradigm suggests that men and women are physiologically different and react to stress differently, with men showing greater reactivity to stressful stimuli. Men, therefore, may withdraw from conflict to avoid the unpleasant associations of increased arousal (Gottman & Levenson, 1988). This disengagement or withdrawal could be relevant to our study as all the experimenters interacting with the men (both positive and negative) were women. influences such as appraisals and state anxiety. We were especially interested in the more comprehensive measure of psychological processes such as threat. However, 27 free to leave, but may have chosen to stay to satisfy credit or monetary obligations. Instead of withdrawing by leaving the experiment, the male participants' withdrawal may demand-with­withdrawal A second objective in this study was to observe the influence of relationship type on psychological mechanisms and cardiovascular measures. As was previously stated, bringing a network member to the laboratory carries some uncertainties. Our premise in this study asserted that the more controlled laboratory-induced relationships would lend to greater sensitivity within the experiment, allowing us to observe direct mediation despite the more controlled context and comprehensive measures of psychological processes, like prior work, we were not able to identify the pathways responsible for our 28 psychological processes as they occur "online". homogeneous-predominantly 28 significant relationship effects. This inability to establish the pathways responsible for our significant relationship effects however is also an important aspect in the continuing work of identifying the role of social relationships and health outcomes. Future work may need to expand on these and other psychological assessments, including assessments taken at various times during the stress task in order to more fully capture the Limitations Although this study does advance our knowledge of supportive relationships, there are clearly some limitations that should be addressed. First, this was a laboratory setting, lending an artificial quality to the interaction. Additionally, we used a fairly young, healthy population and our sample was fairly homogeneous-predominantly white, low-SES, relatively college-age students. Although blood pressure can be a predictor of future cardiovascular health, whether the blood pressure differences we saw in our youthful population are indicative of actual cardiovascular risk is something that needs further study. Second, we used only female experimenters, lending to possible gender confounds. Further, participants never actually met Experimenter Two who provided the relationship manipulations. Stressful interactions between two people usually take place in the context of an ongoing relationship in everyday life. Our contrived interaction between the participant and an experimenter that the participant had not physically met may not have encouraged participants to view the interaction as a "relationship," but rather simply a one-time-only interaction. Future work may need to include more time stress-buffering with the manipulation-experimenter to establish greater feelings of positivity or negativity. In summary, our data suggests that strangers can provide stress-buffering physiological effects although future research will be necessary to determine direct mediation of such social support associations. 29 RREEFFEERREENNCCEESS & 3, Clinical experimental & five-year & 7, & 59, 388-398. J., 11, 31 Acitelli, L. K., & Young, A. M. (1996). Gender and thought in relationships. In G. J. O. Fletcher J. 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