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The effect of social support and physical touch on cardiovascular reactions to mental stress
THE EFFECT OF SOCIAL SUPPORT AND PHYSICAL TOUCH ON CARDIOVASCULAR REACTIONS TO MENTAL STRESS JENNIFER L. EDENS, (Received
16 April
KEVIN
1991;
T. LARKIN
accepted
in revised
and JENNIFER L.
form 12 Se1xemher
ABEL
199 I)
Abstract-To examine the effects of social support on cardiovascular reactions to behavioral stress, the present study tested the relative contribution of three elements of social support: the presence of angther person in the laboratory; the presence of a person considered to be a friend; and physical touch. Sixty undergraduate females were assigned to one of the following groups: alone (A); friend present-touch (FT); friend present-no touch (FNT); stranger present-touch (ST); and stranger present-no touch (SNT). Heart rate (HR), systolic blood pressure @BP), and diastolic blood pressure (DBP) measures were obtained across baseline phases and during presentation of two behavioral challenges (mental arithmetic, mirror-tracing). The findings suggest that neither the presence of a stranger nor physical touch are related to attenuated cardiovascular reactions to stress; rather, if the extent of cardiovascular reactivity is related to social support, the presence of a friend may be the important mediating variable.
INTRODUCTION SOCIALLY supportive interpersonal relationships have been positively linked to cardiovascular health [ 1, 21. Although a great deal of research has examined whether social support exerts a direct influence on the cardiovascular health status of an individual or a buffering influence on the relationship between levels of stress and subsequent health status [ 3-71 , very little is known regarding the physiological mechanisms responsible for the effect of social phenomenon on pathological cellular or vascular cardiovascular conditions. One fertile source of data which has attempted to explain the complex relationship between social/behavioral factors and cardiovascular disease (CVD) involves the examination of cardiovascular reactivity to laboratory stressors. A variety of studies have demonstrated that behaviorally-elicited psychophysiological reactivity may serve as a factor which contributes directly and/or serves as a marker to the pathogenic substrates functioning in the etiology of disorders such as CVD or essential hypertension [ 81. Results of preliminary studies examining the relationship between social support and magnitude of cardiovascular responding to stress have indicated that social presence and physical contact is generally related to lower levels bf cardiovascular arousal [ 9-121. Recent research by Unden et al. [7] found that persons reporting low social support in their work environments had significantly higher heart rates during work, leisure, and rest hours than those reporting higher levels of social support. Moreover, it seems that limited exposure to social contact produces psychological and physiological changes which, if chronic, can result in increased morbidity or mortality [ 111 . Extrapolating from these findings, Kamarck er al. [ 131 investigated the effects of non-evaluative social interactions on cardiovascular reactivity. Heart rate (HR),
Address correspondence West Virginia University,
to: Jennifer L. Edens, M.A., Department Morgantown, WV 26506, U.S.A. 371
of Psychology,
104 Oglebay
Hall,
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systolic blood pressure (SBP), and diastolic blood pressure (DBP) were monitored in college-aged women undergoing two laboratory stressorsl mental arithmetic and a concept formation task. Subjects were randomly assigned to one of two conditions. In the ‘alone’ condition, the subject engaged in all laboratory tasks unaccompanied. In the ‘friend’ condition, a pre-designa.ted friend accompanied the subject, silently supported her during the stressors, and touched her on the non-dominant wrist throughout the task. Although no differences in task performance or subjective aEect were observed between subjects in the two conditions, those in fhe ‘friend’ condition showed decreased HR and SBP reactivity to both challenges when compared to subjects in the ‘alone’ condition. Some reduction in diastolic blood pressure (DBP) was present, but was not significant. Given that non-evaluative social support has been hypothesized to reduce the impact of the stress response, these findings are important in identifying psychophysiologic mechanisms (i.e. reduced cardiovascular reactivity) responsible for explaining how social support may moderate the pathogenic process. Although these results indicated that females responded with decreased HR and SBP response to laboratory stressors when touched by a non-evaluative friend during the stressful tasks, it was unclear whether social presence, physical contact, friendship factors, or an interaction of these variables was responsible for the decreased cardiovascular responses. In an effort to replicate the findings of Kamarck et al. [ 13 ] and address the above unanswered questions, the present study examined female students who were instructed to complete two laboratory challenges in one of five experimental conditions: (a) with a non-evaluative, subject-chosen friend present; (b) with a subject-chosen friend present touching the subject on the non-dominant arm; (c) with a non-evaluative, experimenter-chosen stranger present; (d) with an experimenter-chosen stranger present and touching the subject on the non-dominant arm; and (e) with the subject in the laboratory room alone. METHODS Subjects
and design
Sixty female undergraduate student volunteers served as subjects for this study. Potential participants who reported a history of chronic illness, use of medications with cardiovascular effects, or who were smokers were excluded from participation. Also, any individuals reporting prior experience in a study uti!izing mental arithmetic tasks were excluded. Because of a recent report that suggested cardiovascular responses to stressors may be affected by hormonai fluctuations in females [ 141. all subjects were assessed during equivalent phases of their menstrual cycle. Research has also indicated greater magnitudes of reactivity to stressors during the preovulatory phase [ 141, thus all subjects were scheduled during this time. Any females reporting an irregular cycle were excluded from participation. Because family history of cardiovascular disease 1151 and current use of oral synthetic hormones [ 161 have been shown to affect cardiovascular reactions, subject characteristics on these two variables were matched across the five experimental condilions, subjects were matched across the five yielding equal numbers in each group. Following selection, experimental groups: (I) the ‘alone’ (A) condition; (2) the ‘stranger-no touch’ (SNT) condition; (3) the ‘stranger-touch’ (ST) condition; (4) the ‘friend-no touch’ (FNT) conchtion; or (5) the ‘friend-touch (FT) condition. Those assigned to the two ‘friend’ conditions were asked to recruit their closest female friend, heretofore referred to as ‘friend’, who agreed to accompany. the subject to the laboratory session. Only’ same-sex friends were requested in order to decrease reactlvlty based on the potential ambiguity present in opposite-sex interactions. Subjects chosen to participate received 1 hr of course extra credit for the laboratory session. ‘Friends‘ who appeared with subjects during the task received no compensation.
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tasks
Mental arithmetic tusk. The mental arithmetic task was conducted in three consecutive I-min trials, and all digits, instructions. and prompts were presented via a pre-recorded tape. Subjects were given a different four digit number at the beginning of each trial, then requested to perform serial subtraction by 17 aloud. To enhance the subjects’ perceptions of task importance, they were told that both the speed and accuracy of their performance would be evaluated. A prompt to work quickly and accurately was also presented prior to the onset of the second number. Serial 17 subtraction was modeled for the subjects via the taped instructions prior to the onset of the first trial, and the modeled subtraction was performed four times at the rate of approximately one per second. Performance scores for the mental arithmetic task were calculated as a percentage of correct responses to attempted subtractions. hfirror-tracing task. Subjects were presented with the mirror-tracing apparatus and a red pencil. They were requested via taped instructions to trace the out!ine of a six-sided star using only the mirror image of the star as a guide. They were further instructed that accuracy and speed were evaluated; thus, they were urged to trace within the star boundaries but to work as quickly as possible. At one point during the task, subjects were urged by taped instruction to increase the speed and accuracy of their performance. Performance scores for the mirror-tracing task were analyzed two ways. The first score indicated the number of stars that the subject completed. The second score indicated the number of errors the subject made on all stars completed within the trial. Measures
ofcardiovascular
reactivity
Heart rate was monitored during the laboratory session using a Grass photoelectric pulse transducer attached to the index finger of the non-dominant hand. The pulse waves were detected by a Grass 7Pl preamplifier and a Grass Model 7 Polygraph. Systolic and diastolic blood pressures were measured using an IBS automated sphygmomanometer. The standard occluding cuff, which was attached to the subject’s non-dominant arm, was programmed to automatically inflate and deflate every minute; blood pressure was detected by a small microphone array positioned over the brachial artery. Cardiovascular responding was recorded throughout all baseline and task phases by an experimenter located in an adjacent room. Although the experimenter was able to view the subject through a small window between the rooms, the subject was not able to see the experimenter during the session. All communication was conducted through a two-way intercom. Heart rate data was averaged across one minute intervals, and blood pressure readings were taken at the onset of each one minute interval. Measure
ofsocial support
The subjects’ perception of social supportiveness by their chosen ‘friend’ or their ‘best friend’ (for subjects in the Alone or Stranger conditions) was measured using a modified version of the Interpersonal Support Evaluation List (ISEL); [ 171 The original ISEL consists of 40 items comprising four IO-item subscales covering theoretically derived aspects of social support. ‘The subscales include measures of appraisal, belonging, tangible, and self-esteem supports. Adequate internal and test-retest reliabilities have been established for the original form of the ISEL. Discriminant validity between the original ISEL and both social desirability and social anxiety has also been achieved. The ISEL adequately assesses supportiveness throughout the entire social network. However, since the present study sought to evaluate only a single source or support, the original scale was modified to reflect the subjects’ perceptions of supportiveness by their chosen ‘friend’ or their ‘best friend’ (for subjects in the Alone or Stmnger conditions). The modified ‘appraisal support’ subscale examined the subjects’ ability to talk to and confide in their ‘friend’. The perception of availability of their ‘friend’ to do things with the subject was evaluated in the ‘belonging’ subscale. The modified ‘tangible support’ subscale assessed the subjects’ perceived ability to receive material aid from their ‘friend’. Finally, the subjects’ perceptions of their self-worth as compared to their ‘friend’ was examined in the ‘self-esteem’ subscale. All items on the scale were listed in random order and were counterbalanced for positive and negative socially desirable statements.
Screening session. Volunteers were solicited via a notice posted on the subject recruitment bulletin board in the Psychology Building of West Virginia University. Those interested were requested to attend an information and screening session where a Family Medical History Questionnaire was completed to determine the family’s hypertensive status. In addition, a brief screening questionnaire was completed by each potential subject which assessed menstrual cycle variables, health history, drug use, catieine intake, and tobacco use. Following the screening session, eligible volunteers were designated and assigned to one of the five experimental conditrons, with twelve subjects in each group. Subjects were informed that the experimenter would schedule their laboratory session during the preovulatory phase of their next menstrual period; participants in rhe ‘friend’ condition were further
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instructed to contact their chosen partner to inform her of future participation. Lahorrrto~ session. Subjects were requested to abstain from physical exertion and food intake Ihr 1 hr prior to their participation in the laboratory session. They were also requested to refrain from Ingesting caffeine for a minimum of 8 hr prior to their laboratory session. This was confirmed through a self-report checklist administered immediately before the session. Upon their arrival, subjects were briefly oriented to the laboratory and asked about activities engaged in during the last hour. They were then asked to complete the aforementioned self-report checklist and the ISEL. Those individuals in the ‘friend’ conditton were instructed to complete the ISEL with their chosen ‘friend’ in mind. Those in the ‘alone’ and ‘stranger’ conditions were instructed to complete the form with whomever they consider their best friend in mind. The blood pressure cuff and pulse transducer were then attached as described above. and subjects were asked to rest quiet!y for a 15 min adaptation period. The final 6 min of this phase served as the first baseline period (BI ). AII subjects underwent Bl alone regardless of the experimental conditions to which they were assigned. ‘Friends’. if present, waited in a separate room during this period. B!ood pressure and heart rate were monitored as described above. While the subject underwent RI. the experimental protocol and duties were explained to the ‘friend’. Because potential subject fears of negative task performance evaluation by their partner could contaminate the measures of cardiovascular reactivity to the tasks, attempts were made to decrease the evaluative component of the protocol. All ‘friends’ and research assistants serving as ‘strangers’ were provided with portable cassette players, headsets, tapes of white noise, and several magazine articles. Before entering the laboratory they were instructed to sit in a chair positioned within the subject’s view, listen to the tape of white noise, and to peruse the articles for the duration of the tasks. At no time were they permitted to engage the subject in conversation or respond to any statements by the subject. ‘Friends’ participating in a ‘touch’ condition were requested to gently place their hand across the wrist of the subject’s non-dominant hand for the duration of the laboratory phase. Following Bl, subjects in the ‘friend’ and ‘stranger’ conditions were informed that measurement had stopped briefly and their friend or a research assistant would be entering the laboratory. They were informed that their ‘friend’ or a laboratory assistant would be with them to provide silent support while they underwent the experimental tasks. but that their partner would not be able to see or hear their task performance due to the use of earphones and reading materials. For individuals in the ‘touch’ conditions, they were further informed that their partner would be touching them throughout the laboratory sessions as a means of conveying support and comfort. The experimenter then demonstrated by touching the subject on the non-dominant wrist. Subjects in the alone condition were similarly informed that measurement had been stopped. They were instructed to rest quietly for a period of time equal to the break afforded subjects in both the ‘friend’ and ‘stranger’ conditions. A second 6 min resting baseline measure (B2) was then instituted for all subjects to assess for the potential effects of mere social presence on baseline cardiovascular levels. Heart rate and blood pressure were measured as described above. Next, the experimental tasks were presented to all subjects. Because the effect of task upon cardiovascular reactivity was not the focus of the present study, the two tasks were not counter-balanced. First, a mental arithmetic task was presented to all subjects. This was followed by a 1 min recovery period, a 6 min resting baseline (B3), the mirror-tracing task, and another one minute recovery period. During both tasks, the ‘friends’ and ‘strangers’ were instructed that they were to only function as a silent support partner for the subject. In both the ‘friend’ and ‘stranger’ conditions, the designated partner was present throughout both tasks and intervening rest period. Subjects assigned to a control condition completed both laboratory tasks alone. were requested to exit Following the conclusion of the mirror-tracing task, ‘friends’ and ‘strangers’ the laboratory. All subjects were then instructed to rest quietly during the final 6 min baseline period (B4). Heart rate and blood pressure were measured as described above. All instrumentation was than disconnected and subjects were debriefed.
RESULTS
Presentation of the results of this experiment subsumes four groups of analyses. parameters (HR, These included comparison of subjects’ resting cardiovascular SBP, DBP) at all four baseline phases among the five experimental groups (see Tables I-III). The second set of analyses involved contrasting cardiovascular responses (HR, SBP, DBP) of subjects in each group during the mental arithmetic and mirrortracer mental tasks. In the third set of analyses, subjects’ performances on mental tasks were compared across groups. Finally, the fourth analysis contrasted the scores
Social
37.5
support
among all five groups yielded by the four-component measure of social support. Each group of analyses was conducted employing a set of four multivariate planned comparisons. In the first comparison, subjects in the Alone condition were compared with subjects in the remaining four conditions to test for the effect of social presence. In comparison two, subjects in both Touch conditions (FT, ST) were compared with subjects in No-Touch conditions (FNT. SNT) to test for the effect of physical touch. Stranger (ST, SNT) and Friend (FT, FNT) subjects were contrasted in the third comparison to test for the effect of friendship factors. Finally, comparison four examined differences between the Alone and Friend Touch groups. This final comparison was included to determine whether the findings of Kamarck et al. were replicablc. TABLE I.-HEART
Alone M SD
Friend M
B4
79.9 11.7
89.0 10.3
79.0 12.1
82.‘7 11.8
77.2 11.7
89.7 13.8
89.7 14.4
97.4 20.2
90.7 15.5
93.3 15.3
91.3 13.4
83.5 11.2
83.5 12.0
94.5 11.6
85.5 11.4
88.6 9.6
84.7 11.0
85.2 14.7
84.8 14.4
94.5 14.9
85.8 15.4
90.9 16.0
85.9 15.2
82.2 15.4
80.2 14.2
105.9 21.5
83.8 14.0
90.7 15.1
83.2 13.3
77.8 9.5
no-touch
SD
Stranger M
MT
B2
touch
SD
Stranger M
Period MA B3
Bl
no-touch
SD
Friend M
RATE MEANS AND STANDARD DEVIATIONS BY GROUP
touch
SD
Key: Bl = baseline 1; B2 = baseline B3 = baseline 3; MT = mirror-tracer; SD = standard deviation.
2; MA = mental B4 = baseline 4;
arithmetic; M = mean;
TABLE II.-SYSTOLIC BLOOD PRESSURE MEANS AND STANDARD DEVIATIONS BY GROUP
Alone M SD
Friend M
SD
B4
117.0 8.6
117.0 10.8
131.4 10.8
117.4 9.2
126.6 17.9
117.1 10.2
116.2 7.6
115.7 7.2
124.3 6.4
116.4 7.6
123.0 12.8
116.5 8.0
116.0 8.6
115.1 8.0
133.1 12.9
115.1 9.4
121.0 16.2
116.5 6.9
112.6 9.0
113.1 9.6
122.9 12.5
113.2 9.2
122.3 13.6
114.0 10.2
116.3 9.5
115.7 9.3
133.3 11.1
117.7 11.1
122.7 9.8
119.3 8.7
no-touch
SD
Stranger M
MT
touch
SD
Stranger M
B2
no-touch
SD
Friend M
Period MA B3
Bl
touch
Key: Bl = baseline 1; B2 = baseline 83 = baseline 3; MT = mirror-tracer; SD = standard deviation.
2; MA = mental B4 = baseline 4;
arithmetic; M = mean;
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et al
TAHLE III.-DIASTOLIC BLOOD PRESSUKE MEANS AND STANUAKD DEVIATIONS BY GROUT
Alone M SD
Friend iw
SD
75.2 8.7
84.1 8.2
74.4 8.0
75.6 13.6
78.2 12.3
75.1 9.0
74.3 11.2
79.6 12,s
74.6 12.1
75.2 13.7
76.4 9.5
74.4 6.7
74.0 7.7
83.1 8.2
71.8 7.9
70.6 8.1
75.0 3.7
71.6 4.8
72.8 6.0
80.0 7.6
72.5 4.5
73.2 12.2
71.2 7.0
72.4 7.4
72.0 7.7
86.9 10.0
73.2 5.7
79.2 7.5
80.0 8.7
74.8 9.7
no-touch
M SD
Stranger
B4
touch
M Stranger
MT
B2
no-touch
SD
Friend
Period MA I33
Bl
touch
M SD
Key: Bl = baseline I; B2 = baseline B3 = baseline 3; MT = mirror-tracer; SD = standard deviation.
2; MA = mental B4 = baseline 4:
arithmetic:
M = mean;
Planned comparison multivariate analyses employed Wilks’ Lambda and significant effects at the multivariate level were further tested employing planned comparison univariate analyses of variance. Because of an instrumentation failure, blood pressure data from three subjects were lost. Therefore, analyses involving blood pressure data were conducted on only 57 subjects. Cardiovascular
baseline
levels
The overall MANOVA for baseline cardiovascular levels yielded a significant main effect for Period, F (9, 397) = 0.83, p < 0.001; follow-up univariate ANOVAS revealed a significant main effect for Period for HR, F (3. 165) = 3.30, p = 0.02, and DBP, F(3, 165) = 6.59 p < 0.001. Tukey tests indicated that for all subjects mean HR was significantly greater at baseline 3(M = 84.96 bpm) than at baseline 1 (Jkf = 83.68 bpm, p < 0.05). For DBP, the mean level was significantly greater at baseline 4 (M = 76.36 mm Hg) than at baseline 1 (M = 73.66 mm Hg, p < O.Ol), baseline 2 (M = 73.66 mm Hg, p < O.Ol), and baseline 3 (M = 73.3 mm Hg, p < 0.01). Regarding the planned group comparisons, all Group main effects and Group-byPeriod interactions were not significant, (Fs < l), except a significant Group-byPeriod interaction contrasting HRs of subjects in the Alone condition with HRs of subjects in all others conditions, F(3, 165) = 4.2, p = 0.00’7. Mean contrasts indicated that subjects in the ‘Alone’ condition had lower baseline HRs at baseline 4 (&I = 77 18 bpm) and somewhat lower HRs at baseline 1 (M = 77.83 bpm) than subjects in the ‘Other’ condition groups (baseline 4: A4 = 86.25 bpm p < 0.05, baseline 1: A4 = 85.16 bpm, p < 0.05). Because all groups were alone during baselines 1 and 4, these findings were attributed to sampling error. All remaining planned comparisons yielded no significant effects for HR, SBP, or DBP (all Fs < 1).
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Cardiovascular
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support
to mental tasks
Because this study attempted to assess the relative importance of physical touch, presence of another person, and presence of a friend in demonstrating attenuated cardiovascular reactions to stress, the series of four planned comparisons were again undertaken, and were analyzed using a MANCOVA, covarying baseline values immediately preceding each task. Mental arithmetic. The first planned comparison testing the effect of social presence was not significant, F(3,50) = 0.96, p = 0.565. However, the second comparisons testing the effect of physical touch yielded a main effect for Group, F(3,50) = 0.670, p < 0.001. Follow-up univariate analyses revealed main effects for HR, F(1,52) = 7.52,~ = 0.008, SBP, F(1,52) = 12.49,~ < 0.001, and DBP, F(1,52),p < 0.001. Subjects in Touch conditions responded to the stressor with significantly higher adjusted mean HRs (M = 101.8 bpm), SBPs (M = 133.25 mm Hg), and DBPs (M = 85.6 mm Hg) than subjects in the No-Touch conditions: HRs (M = 92.65 bpm), SBPs (M = 123.59 mm Hg), and DBPs (M = 79.9 mm Hg; see Figs l-3). Mental
arithmetic
3tar tracer
120 1 115
, 109
110 H
i
105
R b p m
100 95
‘+L
60 A
FNT
FT
SNT
ST
A
FNT
FT
SNT
ST
Group
FIG. 1. HR responses to the mental arithmetic and mirror-tracer challenges for subjects in the alone (A), friend-touch (FT), friend-no touch (FNT), stranger touch (ST), and stranger-no touch (SNT) groups (covariance adjusted means are depicted). Mental
star tracer
arithmetic
140
135
I
133.3
1
:1
30.1
;
130
P A m H 9
120
115
110
.- II A
FNT
124.8
16
124
125
FT
IIT
ST
A
FNT
FT
SNT
ST
Group
FIG. 2. SBP responses to the mental arithmetic and mirror-tracer challenges for subjects in the alone (A), friend-touch (FT), friend-no touch (FNT), stranger touch (ST), and stranger-no touch (SNT) groups (covariance adjusted means are depicted).
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i ES 3
90
A
FNT
FT
SNT
ST
A
FNT
FT
SNT
ST
Group
FIG. 3. DBP responses to the mental arithmetic and mirror-tracer challenges for subjects in the alone (A), friend-touch (FT), friend-no touch (FNT), stranger touch (ST), and stranger-no touch (SNT) groups (covariance adjusted means are depicted).
The third comparison testing friendship factors also yielded a main effect for Group, F(3,50) = 0.817, p = 0.017, with follow-up univariate ANCOVAs indicating significant main effects for HR, F(1,52) = 5.64, p = 0.021, and DBP, F( 1,52) = 4.45, p = 0.04. With respect to both measures, subjects in the Stranger conditions (ST, SNT) responded to the stressor with significantly higher HRs (M = 100.2 bpm), and DBPs (M = 83.45 mm Hg) than subjects in the Friend conditions (FT, FNT): HR (M = 93.25 bpm), and DBP (M = 81.35 mm Hg). The fourth planned comparison contrasting the FT and A groups revealed no significant effect, F(3,50) = 0.921, p = 0.250. Because of evidence indicating that the FNT group experienced less cardiovascular reactivity to the mental arithmetic task than all other groups, a comparison was undertaken contrasting the FNT and Alone (control) group. Univariate analysis of covariance indicated that no significant effects emerged with respect to HR, F( 1,21) = 0.399, p = 0.535, or DBP, F(1,21) = 2.601, p = 0.122. However, a main effect for SBP emerged, F(1,21) = 6.274, p = 0.021, with subjects in the Alone condition responding to the stressor with higher SBP (M = 131.42 bpm) than subjects in the FNT condition 9M = 124.33 bpm). Mirror-tracer. None of the planned comparisons revealed significant effects for HR, SBP, or DBP (all Fs < 1). Performance
on mental
tusks
Mental arithmetic task. No significant effects were derived from the planned comparison multivariate analyses of the performance scores (all Fs < l), indicating that subjects in all five groups performed comparably. Mirror-tracing task. None of the planned comparisons revealed significant effects (all Fs < 1). Thus, subjects in all groups performed comparably. Social support The four measures of social support; appraisal, gible; were also subjected to a planned comparison
belonging, MANOVA.
self-esteem, and tanNo significant effects
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379
emerged, and the Fs for all comparisons were less than one. This indicated that all five groups were equal regarding the perceived social support of their friend or best friend. DISCUSSION
The results of this study provided evidence which supports the importance of the presence of a friend in moderating cardiovascular responses to stress. The importance of physical touch and mere social contact was not supoported with relation to attenuated cardiovascular responding to stress. In fact, regarding physical touch, an unexpected finding was observed in that individuals who were touched exhibited greater HR, SBP, and DBP responses to the mental arithmetic challenge than their No Touch counterparts, suggesting perhaps a detrimental effect of physical contact. The present findings also failed to replicate the results reported by Kamarck et al. [ 131, both regarding cardiovascular responses to stress and baseline cardiovascular parameters. Examination of baseline data indicated that subjects in the alone condition experienced lower HKs during baseline four when compared with subjects in all other groups. For the most part, however, the experimental groups did not differ on cardiovascular levels during baseline phases. Overall, these findings indicated that the mere presence of either a friend or a stranger (either touching or not touching the subject) which occurred during baseline 2 and 3 for subjects in the stranger touch, stranger no-touch, friend touch, and friend no-touch groups did not affect tonic cardiovascular level (i.e. HR, SBP, or DBP). These findings differ slightly from those reported by Kamarck et al. [ 131. Although Kamarck et al. [ 131 found no differences in basal HR or DBP between friend touch and alone subjects, a slight upward trend in SBP across baseline for alone subjects and a slight downward trend in SBP for friend touch subjects was reported showing a small effect for social support on basal measures of SBP. Because the current data resulted in findings inconsistent with Kamarck et al. [ 131, several differences between studies were considered. First, it seems intuitively apparent that the presence of an unknown individual, particularly if that stranger is physically touching you, should elicit some level of stress, anxiety, or discomfort. This phenomenon should be particularly apparent during task presentation. Anecdotal reports from both subjects and laboratory assistants upon leaving the laboratory indicated higher subjective stress levels and increases in stress-indicative behaviors (lack of eye contact, scanning, increased voice tremulousness) for subjects in the stranger-touch condition. Second, further consideration must also be given to possible methodological incongruencies between the current study and the investigation by Kamarck et al. [ 131. While both studies utilized almost identical protocols, the Kamarck et d. [ 131 study used male experimenters interacting with female subjects. In addition, that study was conducted by a professor in a sophisticated laboratory setting. In contrast, the current study involved exclusively female-to-female interactions, was conducted by a graduate student, and was undertaken in a university laboratory setting. Other potentially influential factors also need to be considered. Differences in
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variability, as evidenced by standard deviations, may have also contributed to inconsistent findings between the present and previous work, making statistical comparisons less likely to be significant. Subjects in the alone condition responded with much greater variation across cardiovascular measures than subjects in the other conditions. This increased variability is also greater when compared to variation reported in previous studies. This increased variability may also be related to the sample size employed in the present study. The Kamarck et al. [ 131 study utilized a slightly larger sample size than did the current study, and this may have influenced the results. Their study included 19-20 subjects per cell, while the current study included 12 per cell. However, a power analysis performed prior to the onset of data collection indicated an adequate sample size to detect the magnitude of differences observed by Kamarck ef al. [ 131. Also, overall sample differences between the subject pool at the University of Pittsburgh, where the Kamarck ef al. [ 131 study was undertaken, and the subject pool at West Virginia University, where the current study was undertaken, may have influenced the results. Social support may mean different things to individuals in urban university settings, in comparison to the social atmosphere in West Virginia. The calculation of baseline-to-task change scores for HR and BP parameters were reported by Kamarck et al. [ 131 to compare cardiovascular reactions of women to behavioral challenges across studies. An examination of the change scores from the current data indicated that subjects in the alone condition responded to the mental arithmetic challenge with lower HR and BP measures when compared with previous work. For example, HR reactions of previous studies have ranged from 11.5-17.8 bpm and SBP and DBP reactions have ranged from 18.7-20.7 mm Hg, respectively. In contrast, subjects in the alone condition this study exhibited a 9.1 bpm increase in HR, a 14.5 mm Hg in SBP, and a 8.9 mrn Hg increase in DBP. Lending further support to this argument, post hoc comparisons of responses to the mental arithmetic stressor between the Alone (control) and FNT (‘most helpful’) conditions indicated non-significant differences with respect to HR and DBP responses to the stressor. Had the Alone condition responded consistent with past studies, significant differences between these two groups would have been expected to emerge. The discrepancy in the change scores emanating from the two studies necessitates further consideration. Had the reactions of subjects in the alone condition been comparable with those found in the Kamarck et al. [ 131 study, it seems likely that the present findings would have replicated previous work in addition to demonstrating the importance of friendship factors in modulating the magnitude of cardiovascular responses. The influence of many of the aforementioned factors limit the generalizability of this study. Additionally, clarification of the mechanisms which underlie the effects observed in this study still remain to be elucidated. However, the procedures employed in this and the Kamarck et al. [ 131 study do provide a useful laboratory model for future investigation of the interactive roles of socially supportive variables and cardiovascular responses to stress. Additionally work to highlight the mediating variables of social support is crucial. Replication of the current findings, as well as delineation of both qualitative and quantitative criteria necessary for successful ‘friend’ support and gender influences represent some of the next important steps in this area.
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support
381
With current health concerns focusing on amelioration of lifestyle disease risk, investigations of this nature may provide insight towards a consistent, protective mechanism associated with social support which may be integrated into daily life. The hypothesized result would include increased longevity through social integration. To facilitate research in this area, future investigations should focus on replication and extension of current studies. In addition, gender effects on cardiovascular reactivity to stress in light of socially supportive variables should be examined, as both of the current studies used females. Finally, the duration and type of social affiliation should be considered with respect to future research, as these areas may also provide useful avenues to the protective role of social support in the face of stress. REFERENCES 1. BERKMAN LF, SYME SL. Social networks, host resistance, and mortality: A nine-year follow-up study of Alameda County residents. Am J Epidemiol 1979; 109: 186-204. 2. MEDALIE JH, GOL~BOURT U. Angina pectoris among 10,000 men: II. Psychosocial and other risk factors as evidenced by multivariate analysis of a five year incidence study. Am J Med 1976; 60: 910-919. 3. HOUSE JS, ROBBINS C, METZNER HL. The association of social relationships and activities with mortality: Prospective evidence from the Tecumseh community health study. Am J Epidemiol 1982; 116: 123-140. 4. KAPLAN GA. COHEN BA, COHEN RD, GIJRALNIK J. The decline in ischemic heart disease mortality: Prospective evidence from the Alameda county study. Am J Epidemiol 1988; 127: 1131--l 142. 5. ORTH-GOMER K, JOHNSON JV. Social network interaction and mortality: A six year follow-up study of a random sample of the Swedish population. J Chronic Dis 1987; 40: 949-957. 6. SCHOENBACH VJ, KAPLAN BH, FRIEDMAN L, KLEINBAUM DG. Social ties and mortality in Evans County, Georgia. Am J Epidemiol 1986; 123: 577-591. 7. UNDEN AL, ORTH-GOMER K, ELOFSSON S. Cardiovascular effects of social support in the work place: Twenty-four hour ECG monitoring of men and women. Psychosom Med 1991; 53: 50-60. 8. KRANTZ DS. MANUCK SB. Acute psychophysiologic reactivity and risk of cardiovascular disease: A review and methodologic critique. Psycho1 Bull 1984; 96: 435-464. 9. DRESCHER VM, GANTT WH, WHITEHEAD WE. Heart rate in response to touch. Psychosom Med
1980; 42: 559-565. 10. DRESCHER VM, HAYHURST V, WHITEHEAD WE, JOSEPH JA. The effects of tactile stimulation on pulse rate and blood pressure. Biol Psychia? 1982; 17: 1347-1352. 11. HOUSE JS, LANDIS KR, UMBERTSON D. Social relationships and health. Science 1988; 241: 540-544. 12. MANUCK SM, KAPLAN JR, CLARKSON TB. Atherosclerosis, social dominance and cardiovascular reactivity. In Biological and Psychological Factors in Cardiovascular Disease (Edited by SCHMIDT TH, DEMBROSKI TM, BLUMCHEN G) pp. 459-474. Berlin: Springer, 1986. 13. KAMARCK TW, MANUCK SB, JENNINGS BR. Social support reduces cardiovascular reactivity to psychological challenge: A laboratory model. Psychosom Med 1990; 52: 42-58. 14. POLOFRONE JM, MANUCK SB. Effects of menstrual phase and parental history of hypertension on cardiovascular responses to cognitive challenge. Psychosom Med 1988; 50: 23-36. 15. JORGENSON RS, HOUSTON BK. Family history of hypertension, gender, and cardiovascular reactivity and stereotypy during stress. J Behav Med 1981; 4: 175-189. 16. VON EIFF AW, PLOTZ EJ, BECK KJ, CZERNIK A. The effect of estrogens and progestins on blood pressure regulation of normotensive women. Am J Obstet Gynecol 1971; 109: 887-892. 17. COHEN S, MERMELSTEIN R, KAMARCK TW, HOBERMAN HM. Measuring the functional components of social support. In Social Support: Theory, Research and Application (Edited by SARASON IG, SARASON BR) pp. 73-94. Dordrecht: Marinus Nijohoff, 1985.
16 April
KEVIN
1991;
T. LARKIN
accepted
in revised
and JENNIFER L.
form 12 Se1xemher
ABEL
199 I)
Abstract-To examine the effects of social support on cardiovascular reactions to behavioral stress, the present study tested the relative contribution of three elements of social support: the presence of angther person in the laboratory; the presence of a person considered to be a friend; and physical touch. Sixty undergraduate females were assigned to one of the following groups: alone (A); friend present-touch (FT); friend present-no touch (FNT); stranger present-touch (ST); and stranger present-no touch (SNT). Heart rate (HR), systolic blood pressure @BP), and diastolic blood pressure (DBP) measures were obtained across baseline phases and during presentation of two behavioral challenges (mental arithmetic, mirror-tracing). The findings suggest that neither the presence of a stranger nor physical touch are related to attenuated cardiovascular reactions to stress; rather, if the extent of cardiovascular reactivity is related to social support, the presence of a friend may be the important mediating variable.
INTRODUCTION SOCIALLY supportive interpersonal relationships have been positively linked to cardiovascular health [ 1, 21. Although a great deal of research has examined whether social support exerts a direct influence on the cardiovascular health status of an individual or a buffering influence on the relationship between levels of stress and subsequent health status [ 3-71 , very little is known regarding the physiological mechanisms responsible for the effect of social phenomenon on pathological cellular or vascular cardiovascular conditions. One fertile source of data which has attempted to explain the complex relationship between social/behavioral factors and cardiovascular disease (CVD) involves the examination of cardiovascular reactivity to laboratory stressors. A variety of studies have demonstrated that behaviorally-elicited psychophysiological reactivity may serve as a factor which contributes directly and/or serves as a marker to the pathogenic substrates functioning in the etiology of disorders such as CVD or essential hypertension [ 81. Results of preliminary studies examining the relationship between social support and magnitude of cardiovascular responding to stress have indicated that social presence and physical contact is generally related to lower levels bf cardiovascular arousal [ 9-121. Recent research by Unden et al. [7] found that persons reporting low social support in their work environments had significantly higher heart rates during work, leisure, and rest hours than those reporting higher levels of social support. Moreover, it seems that limited exposure to social contact produces psychological and physiological changes which, if chronic, can result in increased morbidity or mortality [ 111 . Extrapolating from these findings, Kamarck er al. [ 131 investigated the effects of non-evaluative social interactions on cardiovascular reactivity. Heart rate (HR),
Address correspondence West Virginia University,
to: Jennifer L. Edens, M.A., Department Morgantown, WV 26506, U.S.A. 371
of Psychology,
104 Oglebay
Hall,
312
J. L.
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et al
systolic blood pressure (SBP), and diastolic blood pressure (DBP) were monitored in college-aged women undergoing two laboratory stressorsl mental arithmetic and a concept formation task. Subjects were randomly assigned to one of two conditions. In the ‘alone’ condition, the subject engaged in all laboratory tasks unaccompanied. In the ‘friend’ condition, a pre-designa.ted friend accompanied the subject, silently supported her during the stressors, and touched her on the non-dominant wrist throughout the task. Although no differences in task performance or subjective aEect were observed between subjects in the two conditions, those in fhe ‘friend’ condition showed decreased HR and SBP reactivity to both challenges when compared to subjects in the ‘alone’ condition. Some reduction in diastolic blood pressure (DBP) was present, but was not significant. Given that non-evaluative social support has been hypothesized to reduce the impact of the stress response, these findings are important in identifying psychophysiologic mechanisms (i.e. reduced cardiovascular reactivity) responsible for explaining how social support may moderate the pathogenic process. Although these results indicated that females responded with decreased HR and SBP response to laboratory stressors when touched by a non-evaluative friend during the stressful tasks, it was unclear whether social presence, physical contact, friendship factors, or an interaction of these variables was responsible for the decreased cardiovascular responses. In an effort to replicate the findings of Kamarck et al. [ 13 ] and address the above unanswered questions, the present study examined female students who were instructed to complete two laboratory challenges in one of five experimental conditions: (a) with a non-evaluative, subject-chosen friend present; (b) with a subject-chosen friend present touching the subject on the non-dominant arm; (c) with a non-evaluative, experimenter-chosen stranger present; (d) with an experimenter-chosen stranger present and touching the subject on the non-dominant arm; and (e) with the subject in the laboratory room alone. METHODS Subjects
and design
Sixty female undergraduate student volunteers served as subjects for this study. Potential participants who reported a history of chronic illness, use of medications with cardiovascular effects, or who were smokers were excluded from participation. Also, any individuals reporting prior experience in a study uti!izing mental arithmetic tasks were excluded. Because of a recent report that suggested cardiovascular responses to stressors may be affected by hormonai fluctuations in females [ 141. all subjects were assessed during equivalent phases of their menstrual cycle. Research has also indicated greater magnitudes of reactivity to stressors during the preovulatory phase [ 141, thus all subjects were scheduled during this time. Any females reporting an irregular cycle were excluded from participation. Because family history of cardiovascular disease 1151 and current use of oral synthetic hormones [ 161 have been shown to affect cardiovascular reactions, subject characteristics on these two variables were matched across the five experimental condilions, subjects were matched across the five yielding equal numbers in each group. Following selection, experimental groups: (I) the ‘alone’ (A) condition; (2) the ‘stranger-no touch’ (SNT) condition; (3) the ‘stranger-touch’ (ST) condition; (4) the ‘friend-no touch’ (FNT) conchtion; or (5) the ‘friend-touch (FT) condition. Those assigned to the two ‘friend’ conditions were asked to recruit their closest female friend, heretofore referred to as ‘friend’, who agreed to accompany. the subject to the laboratory session. Only’ same-sex friends were requested in order to decrease reactlvlty based on the potential ambiguity present in opposite-sex interactions. Subjects chosen to participate received 1 hr of course extra credit for the laboratory session. ‘Friends‘ who appeared with subjects during the task received no compensation.
Social Experimental
support
313
tasks
Mental arithmetic tusk. The mental arithmetic task was conducted in three consecutive I-min trials, and all digits, instructions. and prompts were presented via a pre-recorded tape. Subjects were given a different four digit number at the beginning of each trial, then requested to perform serial subtraction by 17 aloud. To enhance the subjects’ perceptions of task importance, they were told that both the speed and accuracy of their performance would be evaluated. A prompt to work quickly and accurately was also presented prior to the onset of the second number. Serial 17 subtraction was modeled for the subjects via the taped instructions prior to the onset of the first trial, and the modeled subtraction was performed four times at the rate of approximately one per second. Performance scores for the mental arithmetic task were calculated as a percentage of correct responses to attempted subtractions. hfirror-tracing task. Subjects were presented with the mirror-tracing apparatus and a red pencil. They were requested via taped instructions to trace the out!ine of a six-sided star using only the mirror image of the star as a guide. They were further instructed that accuracy and speed were evaluated; thus, they were urged to trace within the star boundaries but to work as quickly as possible. At one point during the task, subjects were urged by taped instruction to increase the speed and accuracy of their performance. Performance scores for the mirror-tracing task were analyzed two ways. The first score indicated the number of stars that the subject completed. The second score indicated the number of errors the subject made on all stars completed within the trial. Measures
ofcardiovascular
reactivity
Heart rate was monitored during the laboratory session using a Grass photoelectric pulse transducer attached to the index finger of the non-dominant hand. The pulse waves were detected by a Grass 7Pl preamplifier and a Grass Model 7 Polygraph. Systolic and diastolic blood pressures were measured using an IBS automated sphygmomanometer. The standard occluding cuff, which was attached to the subject’s non-dominant arm, was programmed to automatically inflate and deflate every minute; blood pressure was detected by a small microphone array positioned over the brachial artery. Cardiovascular responding was recorded throughout all baseline and task phases by an experimenter located in an adjacent room. Although the experimenter was able to view the subject through a small window between the rooms, the subject was not able to see the experimenter during the session. All communication was conducted through a two-way intercom. Heart rate data was averaged across one minute intervals, and blood pressure readings were taken at the onset of each one minute interval. Measure
ofsocial support
The subjects’ perception of social supportiveness by their chosen ‘friend’ or their ‘best friend’ (for subjects in the Alone or Stranger conditions) was measured using a modified version of the Interpersonal Support Evaluation List (ISEL); [ 171 The original ISEL consists of 40 items comprising four IO-item subscales covering theoretically derived aspects of social support. ‘The subscales include measures of appraisal, belonging, tangible, and self-esteem supports. Adequate internal and test-retest reliabilities have been established for the original form of the ISEL. Discriminant validity between the original ISEL and both social desirability and social anxiety has also been achieved. The ISEL adequately assesses supportiveness throughout the entire social network. However, since the present study sought to evaluate only a single source or support, the original scale was modified to reflect the subjects’ perceptions of supportiveness by their chosen ‘friend’ or their ‘best friend’ (for subjects in the Alone or Stmnger conditions). The modified ‘appraisal support’ subscale examined the subjects’ ability to talk to and confide in their ‘friend’. The perception of availability of their ‘friend’ to do things with the subject was evaluated in the ‘belonging’ subscale. The modified ‘tangible support’ subscale assessed the subjects’ perceived ability to receive material aid from their ‘friend’. Finally, the subjects’ perceptions of their self-worth as compared to their ‘friend’ was examined in the ‘self-esteem’ subscale. All items on the scale were listed in random order and were counterbalanced for positive and negative socially desirable statements.
Screening session. Volunteers were solicited via a notice posted on the subject recruitment bulletin board in the Psychology Building of West Virginia University. Those interested were requested to attend an information and screening session where a Family Medical History Questionnaire was completed to determine the family’s hypertensive status. In addition, a brief screening questionnaire was completed by each potential subject which assessed menstrual cycle variables, health history, drug use, catieine intake, and tobacco use. Following the screening session, eligible volunteers were designated and assigned to one of the five experimental conditrons, with twelve subjects in each group. Subjects were informed that the experimenter would schedule their laboratory session during the preovulatory phase of their next menstrual period; participants in rhe ‘friend’ condition were further
374
J. L. EDENS et al.
instructed to contact their chosen partner to inform her of future participation. Lahorrrto~ session. Subjects were requested to abstain from physical exertion and food intake Ihr 1 hr prior to their participation in the laboratory session. They were also requested to refrain from Ingesting caffeine for a minimum of 8 hr prior to their laboratory session. This was confirmed through a self-report checklist administered immediately before the session. Upon their arrival, subjects were briefly oriented to the laboratory and asked about activities engaged in during the last hour. They were then asked to complete the aforementioned self-report checklist and the ISEL. Those individuals in the ‘friend’ conditton were instructed to complete the ISEL with their chosen ‘friend’ in mind. Those in the ‘alone’ and ‘stranger’ conditions were instructed to complete the form with whomever they consider their best friend in mind. The blood pressure cuff and pulse transducer were then attached as described above. and subjects were asked to rest quiet!y for a 15 min adaptation period. The final 6 min of this phase served as the first baseline period (BI ). AII subjects underwent Bl alone regardless of the experimental conditions to which they were assigned. ‘Friends’. if present, waited in a separate room during this period. B!ood pressure and heart rate were monitored as described above. While the subject underwent RI. the experimental protocol and duties were explained to the ‘friend’. Because potential subject fears of negative task performance evaluation by their partner could contaminate the measures of cardiovascular reactivity to the tasks, attempts were made to decrease the evaluative component of the protocol. All ‘friends’ and research assistants serving as ‘strangers’ were provided with portable cassette players, headsets, tapes of white noise, and several magazine articles. Before entering the laboratory they were instructed to sit in a chair positioned within the subject’s view, listen to the tape of white noise, and to peruse the articles for the duration of the tasks. At no time were they permitted to engage the subject in conversation or respond to any statements by the subject. ‘Friends’ participating in a ‘touch’ condition were requested to gently place their hand across the wrist of the subject’s non-dominant hand for the duration of the laboratory phase. Following Bl, subjects in the ‘friend’ and ‘stranger’ conditions were informed that measurement had stopped briefly and their friend or a research assistant would be entering the laboratory. They were informed that their ‘friend’ or a laboratory assistant would be with them to provide silent support while they underwent the experimental tasks. but that their partner would not be able to see or hear their task performance due to the use of earphones and reading materials. For individuals in the ‘touch’ conditions, they were further informed that their partner would be touching them throughout the laboratory sessions as a means of conveying support and comfort. The experimenter then demonstrated by touching the subject on the non-dominant wrist. Subjects in the alone condition were similarly informed that measurement had been stopped. They were instructed to rest quietly for a period of time equal to the break afforded subjects in both the ‘friend’ and ‘stranger’ conditions. A second 6 min resting baseline measure (B2) was then instituted for all subjects to assess for the potential effects of mere social presence on baseline cardiovascular levels. Heart rate and blood pressure were measured as described above. Next, the experimental tasks were presented to all subjects. Because the effect of task upon cardiovascular reactivity was not the focus of the present study, the two tasks were not counter-balanced. First, a mental arithmetic task was presented to all subjects. This was followed by a 1 min recovery period, a 6 min resting baseline (B3), the mirror-tracing task, and another one minute recovery period. During both tasks, the ‘friends’ and ‘strangers’ were instructed that they were to only function as a silent support partner for the subject. In both the ‘friend’ and ‘stranger’ conditions, the designated partner was present throughout both tasks and intervening rest period. Subjects assigned to a control condition completed both laboratory tasks alone. were requested to exit Following the conclusion of the mirror-tracing task, ‘friends’ and ‘strangers’ the laboratory. All subjects were then instructed to rest quietly during the final 6 min baseline period (B4). Heart rate and blood pressure were measured as described above. All instrumentation was than disconnected and subjects were debriefed.
RESULTS
Presentation of the results of this experiment subsumes four groups of analyses. parameters (HR, These included comparison of subjects’ resting cardiovascular SBP, DBP) at all four baseline phases among the five experimental groups (see Tables I-III). The second set of analyses involved contrasting cardiovascular responses (HR, SBP, DBP) of subjects in each group during the mental arithmetic and mirrortracer mental tasks. In the third set of analyses, subjects’ performances on mental tasks were compared across groups. Finally, the fourth analysis contrasted the scores
Social
37.5
support
among all five groups yielded by the four-component measure of social support. Each group of analyses was conducted employing a set of four multivariate planned comparisons. In the first comparison, subjects in the Alone condition were compared with subjects in the remaining four conditions to test for the effect of social presence. In comparison two, subjects in both Touch conditions (FT, ST) were compared with subjects in No-Touch conditions (FNT. SNT) to test for the effect of physical touch. Stranger (ST, SNT) and Friend (FT, FNT) subjects were contrasted in the third comparison to test for the effect of friendship factors. Finally, comparison four examined differences between the Alone and Friend Touch groups. This final comparison was included to determine whether the findings of Kamarck et al. were replicablc. TABLE I.-HEART
Alone M SD
Friend M
B4
79.9 11.7
89.0 10.3
79.0 12.1
82.‘7 11.8
77.2 11.7
89.7 13.8
89.7 14.4
97.4 20.2
90.7 15.5
93.3 15.3
91.3 13.4
83.5 11.2
83.5 12.0
94.5 11.6
85.5 11.4
88.6 9.6
84.7 11.0
85.2 14.7
84.8 14.4
94.5 14.9
85.8 15.4
90.9 16.0
85.9 15.2
82.2 15.4
80.2 14.2
105.9 21.5
83.8 14.0
90.7 15.1
83.2 13.3
77.8 9.5
no-touch
SD
Stranger M
MT
B2
touch
SD
Stranger M
Period MA B3
Bl
no-touch
SD
Friend M
RATE MEANS AND STANDARD DEVIATIONS BY GROUP
touch
SD
Key: Bl = baseline 1; B2 = baseline B3 = baseline 3; MT = mirror-tracer; SD = standard deviation.
2; MA = mental B4 = baseline 4;
arithmetic; M = mean;
TABLE II.-SYSTOLIC BLOOD PRESSURE MEANS AND STANDARD DEVIATIONS BY GROUP
Alone M SD
Friend M
SD
B4
117.0 8.6
117.0 10.8
131.4 10.8
117.4 9.2
126.6 17.9
117.1 10.2
116.2 7.6
115.7 7.2
124.3 6.4
116.4 7.6
123.0 12.8
116.5 8.0
116.0 8.6
115.1 8.0
133.1 12.9
115.1 9.4
121.0 16.2
116.5 6.9
112.6 9.0
113.1 9.6
122.9 12.5
113.2 9.2
122.3 13.6
114.0 10.2
116.3 9.5
115.7 9.3
133.3 11.1
117.7 11.1
122.7 9.8
119.3 8.7
no-touch
SD
Stranger M
MT
touch
SD
Stranger M
B2
no-touch
SD
Friend M
Period MA B3
Bl
touch
Key: Bl = baseline 1; B2 = baseline 83 = baseline 3; MT = mirror-tracer; SD = standard deviation.
2; MA = mental B4 = baseline 4;
arithmetic; M = mean;
J. L. EDENS
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et al
TAHLE III.-DIASTOLIC BLOOD PRESSUKE MEANS AND STANUAKD DEVIATIONS BY GROUT
Alone M SD
Friend iw
SD
75.2 8.7
84.1 8.2
74.4 8.0
75.6 13.6
78.2 12.3
75.1 9.0
74.3 11.2
79.6 12,s
74.6 12.1
75.2 13.7
76.4 9.5
74.4 6.7
74.0 7.7
83.1 8.2
71.8 7.9
70.6 8.1
75.0 3.7
71.6 4.8
72.8 6.0
80.0 7.6
72.5 4.5
73.2 12.2
71.2 7.0
72.4 7.4
72.0 7.7
86.9 10.0
73.2 5.7
79.2 7.5
80.0 8.7
74.8 9.7
no-touch
M SD
Stranger
B4
touch
M Stranger
MT
B2
no-touch
SD
Friend
Period MA I33
Bl
touch
M SD
Key: Bl = baseline I; B2 = baseline B3 = baseline 3; MT = mirror-tracer; SD = standard deviation.
2; MA = mental B4 = baseline 4:
arithmetic:
M = mean;
Planned comparison multivariate analyses employed Wilks’ Lambda and significant effects at the multivariate level were further tested employing planned comparison univariate analyses of variance. Because of an instrumentation failure, blood pressure data from three subjects were lost. Therefore, analyses involving blood pressure data were conducted on only 57 subjects. Cardiovascular
baseline
levels
The overall MANOVA for baseline cardiovascular levels yielded a significant main effect for Period, F (9, 397) = 0.83, p < 0.001; follow-up univariate ANOVAS revealed a significant main effect for Period for HR, F (3. 165) = 3.30, p = 0.02, and DBP, F(3, 165) = 6.59 p < 0.001. Tukey tests indicated that for all subjects mean HR was significantly greater at baseline 3(M = 84.96 bpm) than at baseline 1 (Jkf = 83.68 bpm, p < 0.05). For DBP, the mean level was significantly greater at baseline 4 (M = 76.36 mm Hg) than at baseline 1 (M = 73.66 mm Hg, p < O.Ol), baseline 2 (M = 73.66 mm Hg, p < O.Ol), and baseline 3 (M = 73.3 mm Hg, p < 0.01). Regarding the planned group comparisons, all Group main effects and Group-byPeriod interactions were not significant, (Fs < l), except a significant Group-byPeriod interaction contrasting HRs of subjects in the Alone condition with HRs of subjects in all others conditions, F(3, 165) = 4.2, p = 0.00’7. Mean contrasts indicated that subjects in the ‘Alone’ condition had lower baseline HRs at baseline 4 (&I = 77 18 bpm) and somewhat lower HRs at baseline 1 (M = 77.83 bpm) than subjects in the ‘Other’ condition groups (baseline 4: A4 = 86.25 bpm p < 0.05, baseline 1: A4 = 85.16 bpm, p < 0.05). Because all groups were alone during baselines 1 and 4, these findings were attributed to sampling error. All remaining planned comparisons yielded no significant effects for HR, SBP, or DBP (all Fs < 1).
Social
Cardiovascular
responses
377
support
to mental tasks
Because this study attempted to assess the relative importance of physical touch, presence of another person, and presence of a friend in demonstrating attenuated cardiovascular reactions to stress, the series of four planned comparisons were again undertaken, and were analyzed using a MANCOVA, covarying baseline values immediately preceding each task. Mental arithmetic. The first planned comparison testing the effect of social presence was not significant, F(3,50) = 0.96, p = 0.565. However, the second comparisons testing the effect of physical touch yielded a main effect for Group, F(3,50) = 0.670, p < 0.001. Follow-up univariate analyses revealed main effects for HR, F(1,52) = 7.52,~ = 0.008, SBP, F(1,52) = 12.49,~ < 0.001, and DBP, F(1,52),p < 0.001. Subjects in Touch conditions responded to the stressor with significantly higher adjusted mean HRs (M = 101.8 bpm), SBPs (M = 133.25 mm Hg), and DBPs (M = 85.6 mm Hg) than subjects in the No-Touch conditions: HRs (M = 92.65 bpm), SBPs (M = 123.59 mm Hg), and DBPs (M = 79.9 mm Hg; see Figs l-3). Mental
arithmetic
3tar tracer
120 1 115
, 109
110 H
i
105
R b p m
100 95
‘+L
60 A
FNT
FT
SNT
ST
A
FNT
FT
SNT
ST
Group
FIG. 1. HR responses to the mental arithmetic and mirror-tracer challenges for subjects in the alone (A), friend-touch (FT), friend-no touch (FNT), stranger touch (ST), and stranger-no touch (SNT) groups (covariance adjusted means are depicted). Mental
star tracer
arithmetic
140
135
I
133.3
1
:1
30.1
;
130
P A m H 9
120
115
110
.- II A
FNT
124.8
16
124
125
FT
IIT
ST
A
FNT
FT
SNT
ST
Group
FIG. 2. SBP responses to the mental arithmetic and mirror-tracer challenges for subjects in the alone (A), friend-touch (FT), friend-no touch (FNT), stranger touch (ST), and stranger-no touch (SNT) groups (covariance adjusted means are depicted).
378
J.
95
L.
EDENS
et al.
i ES 3
90
A
FNT
FT
SNT
ST
A
FNT
FT
SNT
ST
Group
FIG. 3. DBP responses to the mental arithmetic and mirror-tracer challenges for subjects in the alone (A), friend-touch (FT), friend-no touch (FNT), stranger touch (ST), and stranger-no touch (SNT) groups (covariance adjusted means are depicted).
The third comparison testing friendship factors also yielded a main effect for Group, F(3,50) = 0.817, p = 0.017, with follow-up univariate ANCOVAs indicating significant main effects for HR, F(1,52) = 5.64, p = 0.021, and DBP, F( 1,52) = 4.45, p = 0.04. With respect to both measures, subjects in the Stranger conditions (ST, SNT) responded to the stressor with significantly higher HRs (M = 100.2 bpm), and DBPs (M = 83.45 mm Hg) than subjects in the Friend conditions (FT, FNT): HR (M = 93.25 bpm), and DBP (M = 81.35 mm Hg). The fourth planned comparison contrasting the FT and A groups revealed no significant effect, F(3,50) = 0.921, p = 0.250. Because of evidence indicating that the FNT group experienced less cardiovascular reactivity to the mental arithmetic task than all other groups, a comparison was undertaken contrasting the FNT and Alone (control) group. Univariate analysis of covariance indicated that no significant effects emerged with respect to HR, F( 1,21) = 0.399, p = 0.535, or DBP, F(1,21) = 2.601, p = 0.122. However, a main effect for SBP emerged, F(1,21) = 6.274, p = 0.021, with subjects in the Alone condition responding to the stressor with higher SBP (M = 131.42 bpm) than subjects in the FNT condition 9M = 124.33 bpm). Mirror-tracer. None of the planned comparisons revealed significant effects for HR, SBP, or DBP (all Fs < 1). Performance
on mental
tusks
Mental arithmetic task. No significant effects were derived from the planned comparison multivariate analyses of the performance scores (all Fs < l), indicating that subjects in all five groups performed comparably. Mirror-tracing task. None of the planned comparisons revealed significant effects (all Fs < 1). Thus, subjects in all groups performed comparably. Social support The four measures of social support; appraisal, gible; were also subjected to a planned comparison
belonging, MANOVA.
self-esteem, and tanNo significant effects
Social support
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emerged, and the Fs for all comparisons were less than one. This indicated that all five groups were equal regarding the perceived social support of their friend or best friend. DISCUSSION
The results of this study provided evidence which supports the importance of the presence of a friend in moderating cardiovascular responses to stress. The importance of physical touch and mere social contact was not supoported with relation to attenuated cardiovascular responding to stress. In fact, regarding physical touch, an unexpected finding was observed in that individuals who were touched exhibited greater HR, SBP, and DBP responses to the mental arithmetic challenge than their No Touch counterparts, suggesting perhaps a detrimental effect of physical contact. The present findings also failed to replicate the results reported by Kamarck et al. [ 131, both regarding cardiovascular responses to stress and baseline cardiovascular parameters. Examination of baseline data indicated that subjects in the alone condition experienced lower HKs during baseline four when compared with subjects in all other groups. For the most part, however, the experimental groups did not differ on cardiovascular levels during baseline phases. Overall, these findings indicated that the mere presence of either a friend or a stranger (either touching or not touching the subject) which occurred during baseline 2 and 3 for subjects in the stranger touch, stranger no-touch, friend touch, and friend no-touch groups did not affect tonic cardiovascular level (i.e. HR, SBP, or DBP). These findings differ slightly from those reported by Kamarck et al. [ 131. Although Kamarck et al. [ 131 found no differences in basal HR or DBP between friend touch and alone subjects, a slight upward trend in SBP across baseline for alone subjects and a slight downward trend in SBP for friend touch subjects was reported showing a small effect for social support on basal measures of SBP. Because the current data resulted in findings inconsistent with Kamarck et al. [ 131, several differences between studies were considered. First, it seems intuitively apparent that the presence of an unknown individual, particularly if that stranger is physically touching you, should elicit some level of stress, anxiety, or discomfort. This phenomenon should be particularly apparent during task presentation. Anecdotal reports from both subjects and laboratory assistants upon leaving the laboratory indicated higher subjective stress levels and increases in stress-indicative behaviors (lack of eye contact, scanning, increased voice tremulousness) for subjects in the stranger-touch condition. Second, further consideration must also be given to possible methodological incongruencies between the current study and the investigation by Kamarck et al. [ 131. While both studies utilized almost identical protocols, the Kamarck et d. [ 131 study used male experimenters interacting with female subjects. In addition, that study was conducted by a professor in a sophisticated laboratory setting. In contrast, the current study involved exclusively female-to-female interactions, was conducted by a graduate student, and was undertaken in a university laboratory setting. Other potentially influential factors also need to be considered. Differences in
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variability, as evidenced by standard deviations, may have also contributed to inconsistent findings between the present and previous work, making statistical comparisons less likely to be significant. Subjects in the alone condition responded with much greater variation across cardiovascular measures than subjects in the other conditions. This increased variability is also greater when compared to variation reported in previous studies. This increased variability may also be related to the sample size employed in the present study. The Kamarck et al. [ 131 study utilized a slightly larger sample size than did the current study, and this may have influenced the results. Their study included 19-20 subjects per cell, while the current study included 12 per cell. However, a power analysis performed prior to the onset of data collection indicated an adequate sample size to detect the magnitude of differences observed by Kamarck ef al. [ 131. Also, overall sample differences between the subject pool at the University of Pittsburgh, where the Kamarck ef al. [ 131 study was undertaken, and the subject pool at West Virginia University, where the current study was undertaken, may have influenced the results. Social support may mean different things to individuals in urban university settings, in comparison to the social atmosphere in West Virginia. The calculation of baseline-to-task change scores for HR and BP parameters were reported by Kamarck et al. [ 131 to compare cardiovascular reactions of women to behavioral challenges across studies. An examination of the change scores from the current data indicated that subjects in the alone condition responded to the mental arithmetic challenge with lower HR and BP measures when compared with previous work. For example, HR reactions of previous studies have ranged from 11.5-17.8 bpm and SBP and DBP reactions have ranged from 18.7-20.7 mm Hg, respectively. In contrast, subjects in the alone condition this study exhibited a 9.1 bpm increase in HR, a 14.5 mm Hg in SBP, and a 8.9 mrn Hg increase in DBP. Lending further support to this argument, post hoc comparisons of responses to the mental arithmetic stressor between the Alone (control) and FNT (‘most helpful’) conditions indicated non-significant differences with respect to HR and DBP responses to the stressor. Had the Alone condition responded consistent with past studies, significant differences between these two groups would have been expected to emerge. The discrepancy in the change scores emanating from the two studies necessitates further consideration. Had the reactions of subjects in the alone condition been comparable with those found in the Kamarck et al. [ 131 study, it seems likely that the present findings would have replicated previous work in addition to demonstrating the importance of friendship factors in modulating the magnitude of cardiovascular responses. The influence of many of the aforementioned factors limit the generalizability of this study. Additionally, clarification of the mechanisms which underlie the effects observed in this study still remain to be elucidated. However, the procedures employed in this and the Kamarck et al. [ 131 study do provide a useful laboratory model for future investigation of the interactive roles of socially supportive variables and cardiovascular responses to stress. Additionally work to highlight the mediating variables of social support is crucial. Replication of the current findings, as well as delineation of both qualitative and quantitative criteria necessary for successful ‘friend’ support and gender influences represent some of the next important steps in this area.
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With current health concerns focusing on amelioration of lifestyle disease risk, investigations of this nature may provide insight towards a consistent, protective mechanism associated with social support which may be integrated into daily life. The hypothesized result would include increased longevity through social integration. To facilitate research in this area, future investigations should focus on replication and extension of current studies. In addition, gender effects on cardiovascular reactivity to stress in light of socially supportive variables should be examined, as both of the current studies used females. Finally, the duration and type of social affiliation should be considered with respect to future research, as these areas may also provide useful avenues to the protective role of social support in the face of stress. REFERENCES 1. BERKMAN LF, SYME SL. Social networks, host resistance, and mortality: A nine-year follow-up study of Alameda County residents. Am J Epidemiol 1979; 109: 186-204. 2. MEDALIE JH, GOL~BOURT U. Angina pectoris among 10,000 men: II. Psychosocial and other risk factors as evidenced by multivariate analysis of a five year incidence study. Am J Med 1976; 60: 910-919. 3. HOUSE JS, ROBBINS C, METZNER HL. The association of social relationships and activities with mortality: Prospective evidence from the Tecumseh community health study. Am J Epidemiol 1982; 116: 123-140. 4. KAPLAN GA. COHEN BA, COHEN RD, GIJRALNIK J. The decline in ischemic heart disease mortality: Prospective evidence from the Alameda county study. Am J Epidemiol 1988; 127: 1131--l 142. 5. ORTH-GOMER K, JOHNSON JV. Social network interaction and mortality: A six year follow-up study of a random sample of the Swedish population. J Chronic Dis 1987; 40: 949-957. 6. SCHOENBACH VJ, KAPLAN BH, FRIEDMAN L, KLEINBAUM DG. Social ties and mortality in Evans County, Georgia. Am J Epidemiol 1986; 123: 577-591. 7. UNDEN AL, ORTH-GOMER K, ELOFSSON S. Cardiovascular effects of social support in the work place: Twenty-four hour ECG monitoring of men and women. Psychosom Med 1991; 53: 50-60. 8. KRANTZ DS. MANUCK SB. Acute psychophysiologic reactivity and risk of cardiovascular disease: A review and methodologic critique. Psycho1 Bull 1984; 96: 435-464. 9. DRESCHER VM, GANTT WH, WHITEHEAD WE. Heart rate in response to touch. Psychosom Med
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