Stress management for essential hypertension: Comparison with a minimally effective treatment, predictors of response to treatment, and effects on reactivity

Journol Pnnted

of Ps,rhosomarrc in Great Bntam

Research.

Vol. 31. No. 4. pp. 453462.

1987. 0

0022.3999/87 $3.00 + .OO 1987 Per&mm Journals Ltd.

STRESS MANAGEMENT FOR ESSENTIAL HYPERTENSION: COMPARISON WITH A MINIMALLY EFFECTIVE TREATMENT,

PREDICTORS

TREATMENT,

AND EFFECTS

RAYMOND

M. ZURAWSKI*, (Received

7 August

TIMOTHY

OF RESPONSE

TO

ON REACTIVITY

W. SMITHt$

and B. KENT HOUSTON§

1986; accepted in revised form 22 Januar.v 1987)

Abstract-Few studies of psychological interventions for essential hypertension have incorporated comprehensive coping skills treatment programs, evaluated the efficacy of such programs against credible, minimally effective controls, examined the effects of these interventions on pressor responses, or clarified the nature of person by treatment interactions. The present study examined the relative effectiveness of multimodal stress management training and a minimally effective treatment control (i.e. GSR biofeedback training) in the treatment of essential hypertensives’ blood pressure at rest and in response to simulated stressful interpersonal situations. At the conclusion of an 8 week training period, stress management participants exhibited reliably lower resting diastolic blood pressure and tended to exhibit lower systolic pressure than controls. The former condition maintained their lower pressures through a h-month follow-up period, but decreases in controls over follow-up rendered the conditions equivalent in blood pressure. No differences between conditions emerged in analyses on pressor responses. Stress management training was somewhat more effective for individuals scoring low rather than high on measures of trait aniety and irritability.

INTRODUCTION SEVERAL reviews of the literature have appeared that suggest that relaxation training and related techniques are effective in the treatment of essential hypertension [lL4]. Seer’s [4] insightful review contains important recommendations for future studies in the area. These recommendations include (a) incorporation of more comprehensive, active, coping skills programs, (b) inclusion of credible attention-placebo control conditions, (c) examination of the generalization of effects, and (d) investigation of individual differences which may predict response to treatment. The present study was designed to address these recommendations. Concerning the first recommendation mentioned above, the overwhelming majority of studies to date have evaluated passive rather than active, coping skills training. This distinction concerns whether the intervention (a) provided rehearsal in the use of relaxation strategies for reducing stress generated in the treatment setting, and/or (b) instructed individuals to apply relaxation in dealing with in viva stressors. One case study [5] and two controlled outcome studies [6, 71 have featured both rehearsal and application as described above, although several other effective interventions have emphasized the importance of the application of techniques to everyday stress [8, 91. The controlled outcome studies featuring both rehearsal and *Department of Psychology, St. Norbert College, U.S.A. tDepartment of Psychology, University of Utah. U.S.A. *AlI correspondence should be addressed to Dr Smith, Department Utah, Salt Lake City, Utah, 84112, U.S.A. JDepartment of Psychology, University of Kansas, U.S.A. 453

of Psychology,

University

of

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R. M. ZURAWSKI et al.

application used some variant of ‘anxiety management training’ [lo], and found this technique to be effective relative to no treatment controls [6,7]. These preliminary findings suggest that an active, broad-based stress management training program may be beneficial. In the present study, the anxiety management training program was further extended to include a cognitive component making it similar to the program used by Crowther [7] and similar to ‘stress inoculation training’ [ll] and ‘multimodal anxiety management training’ [ 121 which have been used successfully in treating other psychophysiologic disorders [ 13, 141. A number of investigators have compared the effectiveness of relaxation training to that of attention-placebo control conditions with mixed results [15--201. However, no study to date has examined the relative effectiveness of stress management programs including the rehearsal and application components described above and attention-placebo controls. At least one study of a program emphasizing application to stress found the intervention superior to a placebo control condition involving mild physical exercise [9]. GSR biofeedback training was deemed a suitable minimally effective treatment control condition in the present study for several reasons. First, it is not yet clear whether biofeedback of a specific response such as GSR does indeed produce generalized reductions in sympathetic drive [21]. Second, although Pate1 [22] included GSR biofeedback training as a component in her successful comprehensive hypertension treatment program, she has indicated that the GSR biofeedback was the least effective single component of the treatment program (personal communication cited by Blanchard [23]). Thus, the greatest impact of GSR biofeedback in the treatment of essential hypertension may be due to attention-placebo factors such as the credibility of biofeedback [24]. Few studies have examined treatment effects on blood pressure responses to stress in hypertensives. Such investigations are important because antihypertensive medications may not adequately block pressor responses [25], and stress management training may be of particular benefit in this regard. Some of the studies examining this issue suggest that psychological interventions may reduce blood pressure elevations during [22], or immediately following [6] exposure to laboratory stressors, while others reveal no effects on stress reactivity or recovery [8, 261. In the present study, the stressor used to test generalization was a behavioral role-play task designed to simulate naturally occurring stressors more closely than the laboratory stressors used in previous research. Identification of individual differences that predict response to treatment may facilitate assigning persons to those interventions most likely to benefit them. To date, research on this issue has produced interesting but conflicting findings [19. 26-291. These equivocal findings may be a function of differences across studies in (a) the manner in which blood pressure was recorded, (b) the way in which individual difference dimensions were assessed, and (c) the type of outcome measure used. In the present study, three individual difference dimensions (trait anxiety, trait anger, and Type A behavior) were examined for their role in predicting outcome. These dimensions were chosen because the research noted above suggests that at least under certain conditions they may be predictive of outcome of pychological treatment for hypertension. To summarize, the purpose of the present study was to investigate the effectiveness of a multimodal stress management training program relative to a GSR biofeed-

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back minimal treatment control condition in the treatment of essential hypertensives’ blood pressure at rest and in response to simulated stressful interpersonal situations. Because of the equivocal findings in research to date concerning predictors of treatment outcome, no specific predictions were made regarding the relationship between the individual difference dimensions and outcome. METHOD Subjects Participants in the present study were selected from an original sample of 113 individuals listed as hypertensive at a community Public Health Department. Individuals were identified as hypertensive if they exhibited consecutive casual blood pressure readings of 140/90 mm Hg or greater at one of the Department’s free screening clinics. Selection criteria required that participants (a) be under the care of a physician and carry a diagnosis of ‘essential hypertension,’ (b) be between the ages of 18 and 60, (c) not be excessively overweight, and (d) be willing to monitor daily type and dosage of medication taken throughout the project. Twenty-nine individuals meeting these criteria expressed a willingness to participate in a study of behavioral techniques to reduce blood pressure. Subjects were assigned either to a stress management training (SMT) or a GSR biofeedback training control condition (BIO). Two therapists were employed (the first and second authors) and each conducted training for half of the participants in each condition. The therapists employed the same detailed training manuals to ensure standardization of presentation. Assignment of participants to Condition and Therapist was random with the constraint of constituting groups equivalent in sex and weight/height ratio. Of the 29 individuals described above, four withdrew prior to the completion of training leaving 25 for further analyses. Those withdrawing cited time constraints or illness as reasons for their withdrawal. Demographic data on the remaining individuals are presented in Table I. No statistically reliable differences between conditions and/or therapists emerged on any of the demographic variables. All participants were Caucasian and all had been under the care of a physician for their hypertension for at least 6 months. Those receiving anti-hypertensive medication all had been maintained on stable regimens for at least 3 months. Apparatw and instruments The GSR biofeedback training was conducted using Lafayette Instruments Feedback was delivered over headphones in the form of a tone that increased to arousal.

TABLE

I.-CHARACTERISTICSOFSAMPLESUBGROUPS Treatment

conditions

Stress management Therapist n

Age

M= SD =

Weight/height

Medication

1

GSR biofeedback

Therapist

2

Therapist

1

Therapist

7

7

6

5

48.14 10.18

46.86 10.86

46.67 12.14

45.30 12.06

2.10 0.39

2.35 0.24

2.40 0.56

0.52

5x2

5:2

4:2

3:2

3:4

412

2:3

ratio (lb/in.)

M

Sex ratio

Model GSR 5140 units. in pitch in direct relation

= 2.31

(females:males)

status

(medicated:unmedicated) 5:2

2

R.

456

M.

ZUKAWSKI

et al.

During assessment sessions, participants’ systolic and diastolic blood pressure (SBP, DBP) and pulse rate (PR) were recorded by means a digital electronic aneroid sphygmomanometer. This unit (Sears Digital 2153) has been found to be highlv resting and reactive SBP, I _ reliable and valid in measuring DGP and PR [30]. The individual difference dimensions assessed as possible predictors of treatment outcome were anxiety, anger, and Type A behavior. Trait anxiety was measured using the total anxiety score from the Institute for Personality and Ability Testing (IPAT) Anxiety Scale [31]. Trait anger was measured using the irritability subscale of the Buss-Durkee Hostility Inventory [32]. Type A behavior was assessed using the Framingham Type A Scale [40]. Finally, to ascertain whether the SMT and RIO conditions were similar in the attention-placebo factors they engendered, a brief three-item expectancy/credibility questionnaire was administered to all participants at the conclusion of their initial training session. Subjects rated how much they expected their BP to change, how helpful they expected the treatment to be for others with hypertension. and the probability of the training helping them reduce BP. To determine whether subjective impressions concerning credibility or general efficacy of the training changed differentially across conditions, a parallel form of the questionnaire was administered after the final training session.

of

Procedure Assessment sessions. Upon arrival for the pretreatment assessment session, participants received a brief description of the project and completed an informed consent statement. A resting period followed during which participants sat quietly as their physiological responses were recorded. Blood pressure and pulse rate were recorded at 90.set intervals until eight such determinations had been made. Following completion of the rest period, a laboratory assistant introduced the task period with the rationale of attempting to estimate pressor responses in the natural environment. Participants interacted with the assistant in a series of role-play situations. Two neutral situations were presented to familiarize participants with the task. The task phase proper consisted of a series of more ‘demanding’ situations. These situations were presented until four recordings each of blood pressure and pulse rate had been obtained, each at 90-set intervals. To illustrate, one situation described the assistant as an insistent neighbor extending an invitation to a social gathering to the participant who was described as ‘too busy to attend’. During a recovery period, participants sat quietly while four recordings of physiological responses were obtained, each at 90-see intervals. The blood pressure cuff was then removed and participants completed the previously described battery of individual difference measures. Post-treatment and follow-up assessment sessions were identical to the pre-treatment session except that different laboratory assistants and role-play vignettes were employed to prevent habituation and to permit investigation of generalization of treatment effects. Treatment Multimodal Stress Management Truining (SMT). Both SMT and BIO were conducted in eight weekly small group sessions, each lasting 60 to 90 min. In the initial session, SMT participants were told that they would be learning a series of self-control skills to help them better deal with stressful situations which may have been maintaining their high blood pressure. Following this, participants were (a) taught a progressive muscle relaxation exercise [34]. (b) told to practice the technique twice daily in non-stressful situations, (c) told not to apply the technique in stressful situations until their skills had developed further. and (d) given forms on which to document their home practice. Over the next few sessions, the role of cognitions in stressful experiences was discussed and cognitive coping strategies were presented [ll]. Participants were also taught additional relaxation techniques including ‘cue controlled breathing’ [35] and relaxation imagery. Beginning in session four, participants were asked to maintain a diary of stressful situations and of the thoughts and feelings that accompanied them. In-session rehearsal of coping skills was the primary focus of sessions five through eight. These sessions were patterned after the ‘anxiety management training’ model [lo]. Specifically, participants used situations listed on their stress diaries to imaginally reconstruct the proprioceptive. affective, and cognitive cues accompanying stressful situations, and then used their physical and cognitive coping skills in alleviating the tension they had induced. Homework assignments were now expanded to include application of coping skills in viva. Discussion of the rehearsal and application was incorporated to further hone the developing coping skills. To prompt continued pratice and application of skills, periodic phone contacts were made throughout the follow-up phase. GSR Biofeedback Trairting (BZO). The initial session of BIO provided a rationale for biofeedback training and instruction in the use of the biofeedback equipment. The remaining sessions consisted of ‘baseline’ and ‘training’ periods. During baseline periods, participants practiced a ‘mental scanning exercise’, in which they closed their eyes and surveyed their bodies for a variety of sensations. This

Stress management

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exercise served to parallel the relaxation exercises in the SMT condition, to provide a focus for homework assignments, and ostensibly to enhance sensitivity to cues helpful in manipulating the GSR response. To render the exercise minimally effective, participants were taught to scan for a variety of bodily sensations, not simply those commonly associated with relaxation. During training periods, feedback was provided over headphones as previously described. Over the course of the sessions, participants were instructed to increase, decrease, and then alternately increase and decrease arousal. Participants were given the latter instructions ostensibly to enhance greater overall control of the GSR response. Homework assignments consisted of instructions to practice the scanning exercise and were monitored using forms similar to those given to SMT participants. At no time were BIO participants told to apply their strategies in response to imaginally-induced or naturally-occurring stress. To parallel the follow-up contact with SMT participants, periodic phone contacts were scheduled with BIO participants during the follow-up period. Preparation Average computing recordings,

of physiological data values for SBP, DBP, and PR were derived for each period in each assessment session by the mean of the last four determinations of rest period BP and PR, the four task period and the four recovery period readings.

RESULTS

Equivalence of conditions in expectancies and involvement To determine whether the SMT and BIO conditions differed initially in perceived credibility or in the expectations they engendered, t-tests were computed for each of the three items on the expectancy form administered at the end of the first training session. No statistically reliable differences were found between conditions. A similar set of t-tests on each of the items on the expectancy form administered at the end of the final training session again revealed no condition differences. Participants in both conditions perceived their respective training programs as highly credible and were confident that the training program could lower their blood pressure and the blood pressure of others exposed to similar training. A further indication of the similarity of SMT and BIO in non-specific factors emerged in an examination of home practice data. An average of the reported instances of practice per week was calculated for each of the participants in each condition, and subjected to a 2(conditions) by 7(weeks of practice) repeated measures analysis of variance. These analyses yielded no statistically reliable main effects or interactions. Inspection of the means revealed that both SMT and BIO participants reported between eight and nine home practice sessions per week and reported maintaining these rates throughout the training period. Thus, there is ample evidence that SMT and BIO conditions were equivalent in perceived credibility, expectations for successful outcome, and involvement. Relative effectiveness of SMT and BIO In analyzing pre-treatment resting data, raw values were used. These average resting values were used as convariates in analyzing pre-treatment task period data in order to eliminate the influence of resting period level on task period arousal (i.e. the law of initial values; [36]). Similarly, to eliminate the influence of task period arousal on the magnitude of responses during the recovery period (the law of final values; [37]), analyses of pre-treatment recovery period data used pretreatment task period values as a covariate. The analyses of post-treatment and follow-up session data were similar to those described above with the following additions. Analyses of the data for each of the

R. M. ZURAWSKI

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et al.

post-treatment and follow-up periods also included statistical control of subjects’ responses during the corresponding pre-treatment period. This was done to control for any differences between conditions in pre-treatment responses. Thus, the primary analyses were represented by a series of 2(conditions) by 2(medication status) analyses of variance and covariance. However. because the analyses yielded very few main effects or interactions involving medication status, and because these effects did not conform to a consistent pattern, medication status will not be mentioned further. Because of random assignment to conditions, no differences between conditions were expected for pre-treatment measures. Analyses of the pre-treatment data indeed revealed no differences between groups in resting, task, or recovery periods. Post-treatment session. Analyses conducted on resting blood pressures at posttreatment revealed a statistically reliable difference between conditions on DBP, F(1, 20) = 7.47, p = 0.01. Inspection of the means indicated that, as predicted, SMT participants exhibited reliably lower resting DBP than their BIO counterparts (79 mm Hg vs 89 mm Hg). The analyses also revealed a difference between conditions in the expected direction that approached significance on SBP, F(1, 20) = 3.27, p = 0.086, (128 mm Hg vs 136 mm Hg). The mean values for these and other SBP and DBP values are reported in Table II. No other statistically significant differences between conditions were observed during the rest period.

TABLE II. -RAW Stress management

MEAN BLOOD PRESSURE DATA

training

GSR biofeedback

training

Pre-test

Post-test

129.07 17.48

137.89 19.22

136.27 11.81

126.81 13.99

70.34 5.78

80.30 9.54

85.25 17.10

89.36 12.97

79.1’) 8.78

157.64 17.83

142.79 17.84

141.36 18.02

155.86 20.23

143.11 11.03

137.38 18.41

97.64 14.19

86.39 7.51

88.71 7.18

95.86 17.35

93.32 11.08

92.28 15.78

139.66 16.25

130.98 14.34

134.59 16.14

141.14 17.92

136.14 8.69

131.44 16.73

90.35 13.77

80.70 4.94

77.00 12.55

86.59 15.73

86.77 11.77

77.97 7.53

Pre-test

Post-test

137.07 16.22

127.88 15.11

87.14 16.71

Follow-up

Follow-up

Period Resting SBP M= SD= DBP M= SD= Task SBP M= SD= DBP M= SD= Recovery SBP M= SD= DPB M= SD=

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Although no statistically reliable differences between conditions were observed during the post-treatment task period, analyses of recovery period data revealed a trend for subjects in SMT to exhibit lower SBP than subjects in BIO, F(l, 18) = 3.43, p = 0.08. Follow-up session. Three BIO participants failed to take part in the final assessment session. Two of these individuals cited time constraints and one gave no reason. The analyses of blood pressure data revealed no reliable differences between conditions during any of the periods. The equivalence of resting pressures at followup occurred because SMT participants showed substantial decreases from pre- to post-treatment that were maintained through follow-up, while BIO participants showed an equivalent decrease between post-treatment and follow-up sessions (see Table 11). Only one statistically reliable difference between conditons emerged during the follow-up assessment, that occurring on task period PR, F(l, 15) = 5.90, p = 0.028. Examination of the means indicated that SMT participants had higher pulse rates than did those in BIO. Individual difference dimension by treatment interactions To determine whether initial scores on the individual difference dimensions were related to treatment outcome, a series of multiple regression analyses were conducted, one for each dependent measure in each period of the post-treatment and follow-up assessment sessions. In these hierarchical regression analyses, dependent measures served as criterion variables. Covariates (e.g. resting levels) and main effects (Conditions, Individual Difference Scores) were entered on the first step of the equation and the Conditions by Individual Difference score interaction was entered on the second (final) step [38]. The interaction term is a reflection of a differential relationship between individual difference score and treatment outcome depending on the training condition to which the participant had been assigned. Statistically reliable individual difference score by conditions interactions occurred in two instances, both involving DBP during the post-treatment task period (interaction p’s < 0.025). Individuals higher in trait anxiety or trait anger scores evidenced more arousal following treatment than did low anxiety or anger clients, if exposed to SMT, r’s = 0.57, 0.45, respectively. In the BIO condition, neither anxiety nor anger was related to post-treatment, task period DBP (r’s = 0.14, -0.16, respectively). DISCUSSION

The foregoing analyses reflect a mixed picture of the value of SMT relative to a minimally effective treatment control. At post-treatment, SMT appeared to be clearly effective. It produced reliably lower resting DBP, and trends toward lower resting SBP and lower recovery period SBP. The magnitude of these raw DBP decreases was similar to that obtained in previous studies of relaxation-based interventions for hypertension [4]. Such decreases are noteworthy in at least two respects. First, the BIO group served as a very stringent comparison group that certainly controlled for credibility, expectancy and involvement. Second, the pre-treatment blood pressures in this sample were relatively low. McCaffrey and Blanchard [l]

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assert that low pre-treatment pressure may obscure differences between conditions. These findings would seem to suggest that the SMT procedure produced short term decreases in blood pressure beyond effects that could be attributed to credibility or expectations for successful outcome, or non-specific attempts at self-management of stress. However, the follow-up results suggest a more cautious interpretation is in order. Because BIO participants exhibited a substantial decrease in resting BP between post-treatment and follow-up, no differences between SMT and BIO existed at follow-up. Thus, any effects specific to SMT appear to have waned over the followup period, because BP levels in the minimally effective treatment decreased during this period of time. Caution should be exercised in accepting this interpretation, however, given that three subjects in the BIO group were not available for post-testing. Finally, it should be noted that SMT was not more effective than BIO in reducing pressor responses. Both conditions exhibited raw pre- to post-treatment decreases in task period SBP of 13-15 mm Hg. Why these findings occurred is unclear. However, at least three factors may have functioned to attenuate differences between the SMT and BIO conditions. First, as indicated above, the BIO condition may have been more effective than was predicted. Although there was no focus on rehearsal or application of complex coping strategies in this condition, five BIO participants spontaneously reported having applied coping strategies in stressful situations. Hence, despite distinctly different treatment emphases, it seems that at least a portion of BIO participants generated self-control coping strategies similar to those formally taught only in SMT. Second, selection factors may have increased the likelihood of therapeutic changes among the BIO participants. Participants in both conditions were volunteers from a larger pool of hypertensives. Their motivation to participate in a study of behavioral techniques to lower blood pressure may have made the self-generation of effective stress management even in the BIO group more likely. Finally, this same motivation, coupled with the non-specific encouragement toward self-control of stress, may have produced general behavioral changes (i.e. decreased work hours, Unfortunately, these behaviors etc.) which could have reduced blood pressure. were not monitored, so this hypothesis could not be investigated. While the foregoing factors may explain why differences between conditions were somewhat attenuated, it is nonetheless difficult to understand why SMT was somewhat less effective for those scoring high on measures of trait anxiety and irritability. It might be speculated that SMT was a complex and difficult program to implement. Further, chronically anxious or angry individuals could be viewed as confronting situations requiring coping more frequently than those lower in trait anxiety or anger. Thus, the combination of a complex coping strategy and an individual forced to implement coping strategies frequently may have contributed to the greater post-treatment arousal in SMT participants high in trait anxiety or irritability. The results of the present study provide several potential directions for future research. Such research should extend the list of individual difference dimensions that could predict outcome to include physiological as well as psychological factors (family history of hypertension, plasma renin levels, etc.). The fact that SMT was more effective at post-treatment but not at follow-up suggests that future research

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should examine the processes through which these treatments exert their effects. Direct effects may occur in the context of more general shifts in health behaviors and self-control. Continued investigations along these lines have the potential to maximize the demonstrated effectiveness of stress management techniques for the treatment of this disorder. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19.

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