Mindfulness DOI 10.1007/s12671-014-0320-4
ORIGINAL PAPER
A Brief Mindfulness Exercise Reduces Cardiovascular Reactivity During a Laboratory Stressor Paradigm Patrick R. Steffen & Michael J. Larson
# Springer Science+Business Media New York 2014
Abstract Mindfulness meditation is increasingly used in health interventions and may reduce stress and blood pressure. We aimed to investigate the effectiveness of brief mindfulness meditation in reducing cardiovascular reactivity and recovery during a laboratory stressor. We randomly assigned 62 meditation-naïve participants to a mindfulness meditation group or a matched non-mindful listening exercise control group. There were no differences between groups in blood pressure, demographic, or mood variables at baseline. Mindfulness participants showed lower systolic blood pressure following the mindfulness exercise and decreased systolic and diastolic blood pressure reactivity during a speeded math stressor. Specifically, as the stressor progressed, blood pressure in the mindfulness group began to decrease, whereas in the control group, it continued to increase. There were no group differences during recovery. Overall, brief mindfulness meditation reduced cardiovascular reactivity to stress and may be an effective intervention for reducing stress-related blood pressure reactivity. Keywords Stress . Mindfulness . Meditation . Blood pressure . Cardiovascular reactivity
Introduction One third of Americans report experiencing high levels of chronic stress with which they feel they cannot adequately P. R. Steffen (*) Department of Psychology, Brigham Young University, Provo, UT, USA e-mail:
[email protected] M. J. Larson Department of Psychology and Neuroscience Center, Brigham Young University, Provo, UT, USA
cope (Keller et al. 2012; American Psychological Association 2008). Stress negatively impacts health and plays a significant role in the development and progression of cardiovascular disorders such as hypertension (Cohen et al. 2007; Keller et al. 2012; American Psychological Association 2008) and predicts the development of heart disease (Carroll et al. 2012), the leading cause of death in all developed countries (Mathers et al. 2009). In spite of the existence of effective interventions for chronic disorders such as hypertension and heart disease, approximately one half of persons receiving medical treatment fail to fully adhere to treatment recommendations (Centers for Disease Control 2010; Haynes et al. 2008). For example, only 50 % of those with diagnosed hypertension have their blood pressure within desirable limits, often because they do not follow their treatment recommendations as prescribed due to negative side effects (Egan et al. 2010; Ockene et al. 2002). According to the World Health Organization, it is more cost effective to improve adherence than it is to try to improve treatments (World Health Organization 2003). Utilizing treatments with less negative side effects is one possible way to increase treatment adherence and success. Mindfulness meditation is increasingly used as a method to decrease stress and improve health (Chiesa and Serretti 2009, 2010; Grossman et al. 2004; Hofmann et al. 2010). Mindfulness meditation interventions typically last between 8 and 12 weeks, have documented small yet meaningful reductions in stress and blood pressure in clinical populations (i.e., breast cancer) and in healthy populations, and do not have negative side effects (Chiesa and Serretti 2009, 2010; Goldstein et al. 2012; Goyal et al. 2014). Brief mindfulness interventions lasting three to four sessions have also demonstrated reductions in stress, negative mood, and heart rate (Zeidan et al. 2010). Given the difficulties associated with adherence to standard interventions, and research showing that both psychotherapy and medication treatments for mental health difficulties only have a mode of one session to convey information
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and enact change (e.g., Gibbons et al. 2011), brief effective interventions are desirable. Cardiovascular reactivity to stress during brief laboratory stressors is related to health outcomes over time (Chida and Steptoe 2010 for a review). High cardiovascular reactivity to stress and less recovery post-stress predict increased cardiovascular disease risk, including increased carotid intimamedia thickness and increased risk for developing hypertension. The Paced Auditory Serial Addition Task (PASAT; Gronwall et al. 1977), a speeded math task, is a good potential laboratory stressor as it increases perceived stress (Hirvikoski et al. 2011) and blood pressure levels (Carroll et al. 2003, 2011). In the Carroll studies, less blood pressure recovery following completion of the PASAT predicted increased risk of hypertension at subsequent 5- and 12-year follow-up examinations, and predicted mortality over a 16-year period. Therefore, the PASAT provides a good laboratory-based stressor to examine cardiovascular reactivity, the effects of stress on health, as well as for examining potential treatment options, such as mindfulness meditation. Mindfulness meditation involves focusing on the present moment in an open and nonjudgmental way. Although mindfulness meditation derives from Buddhist traditions, it has been adapted for use in Western therapeutic modalities with less emphasis on spiritual concerns and more on achieving a mindful point of view. A number of studies show mindfulness meditation practice related to decreased stress and improved health (see Goldstein et al. 2012; Goyal et al. 2014; Grossman et al. 2004; Hofmann et al. 2010 for reviews). Mindfulnessbased cognitive therapy (MBCT) and mindfulness-based stress reduction (MBSR) are two widely used therapeutic approaches that have incorporated mindfulness meditation. Both of these approaches are associated with significant reductions in self-reported stress relative to controls (Bohlmeijer et al. 2010). Chiesa and Serretti (2009, 2010) hypothesize that mindfulness reduces emotional reactivity and ruminative tendencies and thereby reduces stress responsiveness. Mindfulness meditation significantly reduces perceived stress. Britton et al. (2012) studied the impact of MBCT on stress response. They administered the Trier Social Stress Test (TSST) pre- and post-participation in MBCT to examine changes in stress over an 8-week period compared to a wait list control group. Mindfulness meditation significantly reduced emotional reactivity to social stress. A neuroimaging study, using an 8-week mindfulness stress reduction program, found that decreases in perceived stress were related to decreased amygdala gray matter density (Holzel et al. 2010). In these studies, it appears that mindfulness contributes to stress reduction through improved emotion regulation, which may be the pathway through which mindfulness impacts cardiovascular reactivity (Britton et al. 2012; Nyklicek et al. 2013). Mindfulness meditation reduces blood pressure and cardiovascular reactivity. For example, Nyklicek et al.
(2013) administered a brief laboratory stressor to a community sample before and after 8 weeks of MBSR training using an experimental design. Relative to a waitlist control group, mindfulness meditation reduced overall blood pressure (BP) as well as reduced BP reactivity during the second administration of the laboratory stressor. Campbell et al. (2012) used MBSR to show that those higher in BP at baseline had significant decreases in BP relative to a control group; however, there were no effects for those with low BP at baseline. Carlson et al. (2007) used MBSR to show decreased blood pressure response over time, as well as decreased psychological stress. Reviews of the effects of mindfulness on health conducted by Goldstein et al. (2012), Goyal et al. (2014), Grossman et al. (2004), and Chiesa and Serretti (2009, 2010) indicate that MBSR predicted decreased BP and better health outcomes, particularly in younger and healthy populations suggesting that it may be useful in the prevention of disease. Overall, the research indicates that mindfulness meditation exerts a small but meaningful reductions in stress and cardiovascular reactivity. It is not known, however, the amount of mindfulness meditation that is required for positive health benefits and whether or not brief mindfulness meditation can influence cardiovascular reactivity to a stressor. Given that cardiovascular reactivity to stress is a significant predictor of hypertension and heart disease (Carroll et al. 2003, 2011, 2012; Chida and Steptoe 2010) and over one third of the American population reports experiencing high levels of stress associated with concomitant declines in immune functioning and mental health (American Psychological Association 2008; Keller et al. 2012), effective interventions are sorely needed. A significant benefit of mindfulness is that it is relatively simple to practice (although difficult to master), potentially leading to increased treatment adherence even in novices. The purpose of this study was to examine whether a brief mindfulness exercise could be used to reduce the physiological effects of the stress response. Using a randomized experimental design, we specifically addressed three research questions. First, will engaging in a single-session, brief mindfulness exercise result in reduced blood pressure and heart rate relative to a control group? Second, will a brief mindfulness exercise reduce cardiovascular reactivity to the PASAT laboratory stressor? Third, will a brief mindfulness exercise increase cardiovascular recovery post-stressor?
Method Participants Participants were recruited from undergraduate psychology courses. Upon expressing interest in the study, participants were randomly assigned to either a mindfulness group (n=30; 14 females) or a control group (n=32; 17 females). Sample
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characteristics are presented as a function of experimental group in Table 1. We measured baseline anxiety and depressive symptoms due to previous research that shows depressive and anxiety symptoms can alter cardiovascular stress reactivity (e.g., Carroll et al. 2007). Importantly, the groups did not differ in regard to age, gender distribution, ethnicity, years of education, baseline depression symptoms measured by the Beck Depression Inventory-Second Edition (BDI-II; Beck 1996), or baseline trait anxiety, or state anxiety symptoms as measured by the State-Trait Anxiety Inventory (STAI; Spielberger et al. 1983). No participants had ever engaged in mindfulness meditation practices. The study received Institutional Review Board approval before beginning.
behaviors. The specific tracks were Awareness, A Sixth Sense (time=7:41), and An Ethical Foundation (time=6:30; total passive listening time=14:19). Notably, the mindfulness and control tasks included listening to the same voice (KabatZinn) from the same CDs for approximately the same amount of time. Thus, the primary difference that was manipulated was the participation in a mindfulness task versus passive listening about ethical behaviors and awareness.
Measures Paced Auditory Serial Addition Task
Procedure The experimental and control groups completed the same procedures, with the exception of the mindfulness exercise. Upon arrival for the study participants completed written informed consent followed by a demographic questionnaire and measures of mood (BDI-II; STAI). Following completion of the questionnaires, three baseline blood pressure and heart rate values were collected followed by the mindfulness or control exercise (with the total baseline period lasting approximately 15 min), PASAT stressor task (approximately 8 min), and subsequent recovery period (recovery period was 20 min of sitting in a quiet room). The STAI post-measure was administered immediately after the PASAT was completed. Blood pressure and heart rate readings were taken 2 min apart and averaged together for increased reliability at baseline, minutes 6 and 8 of the mindfulness or control exercise (Early Mindfulness), minutes 12 and 14 of the mindfulness or control exercise (Late Mindfulness), minutes 2 and 4 of the PASAT stressor (Early PASAT), minutes 6 and 8 of the PASAT stressor (Late PASAT), minutes 8 and 10 of the recovery period (Early Recovery), and minutes 18 and 20 of the recovery period (Late Recovery). The experiment took about an hour to complete. Following completion of the study participants were debriefed regarding the purposes of the research and provided either $10 per hour or course credit. To compare brief mindfulness meditation with nonmindfulness in an experimental setting, participants engaged in either passive listening or mindfulness exercises from Jon Kabat-Zinn’s Mindfulness for Beginners two-disk CD set (Kabat-Zinn 2006). Participants in the mindfulness group were provided basic standardized instruction on mindfulness and the importance of focusing on the present moment in an open and nonjudgmental way. They completed the Mindfulness of Breathing exercise from the second CD of KabatZinn’s Mindfulness for Beginners (total time in the exercise was 14:33). Participants in the control group also passively listened to two tracks from the same CD focusing on awareness of the environment and the importance of ethical
The PASAT is a speeded mathematics task originally designed to identify individuals with a head injury and track their recovery (Gronwall 1977). The PASAT is thought to measure speed of information processing, auditory attention, and working memory (Tombaugh 2006). Studies indicate that, due to the speed and complexity of the task, the PASAT can be a stressful experience and it has been used as a laboratory stressor in previous research (e.g., Lejuez et al. 2003; Tanosoto et al. 2012). Participants were presented with a random series of digits from 1 to 9 via recorded voice (ours were presented using an MP3 player on a personal computer). Participants were subsequently instructed to consecutively add the digits such that the current digit is added to the previous digit, not to the sum of the previous two digits. Participants typically complete four blocks of fifty digits each block. To increase difficulty and monotonically manipulate attention load, the interstimulus interval (ISI) decreases across the four blocks from 2.4 s, to 2.2 s, to 1.6 s, and finally 1.2 s. To be efficient with the laboratory stressor, we utilized the fastest 1.6-s and 1.2-s ISI blocks that should be related to the highest stress levels (50 trials for each block for a total of 100 trials). Blood Pressure and Heart Rate Data Acquisition Heart rate, diastolic, and systolic blood pressure data were collected using a Dinamap Model 8100 automated blood pressure monitor (Critikon Corporation, Tampa, FL, USA) that capitalizes on the oscillometric method. Readings were obtained following the specifications of the manufacturer using a cuff that was measured and properly sized to fit on the upper nondominant arm of the participant. Data Analysis Before analyzing the research questions, experimental groups were first compared to examine whether groups were not significantly different at baseline for demographic, blood pressure, and mood variables using independent sample t tests
Mindfulness Table 1 Sample characteristics by experimental group
Age Gender (% female) Ethnicity (% white) Education (years) BDI-II STAI-trait STAI-state pre STAI-state post PASAT % correct first trial PASAT % correct last trial Baseline SBP (mm/Hg) Baseline DBP (mm/Hg) Baseline heart rate (BPM)
Mindfulness (n=30)
Control (n=32)
Analysis
Mean (SD) or % 19.9 (2.0) 47 % 94 % 13.5 (1.4) 6.7 (5.5) 33.1 (9.3) 30.5 (8.1) 28.1 (10.0) 0.60 (0.20) 0.53 (0.18) 116 (10) 68 (7) 77 (13)
Mean (SD) or % 20.6 (2.3) 53 % 94 % 14.1 (1.5) 8.0 (8.6) 35.3 (9.4) 30.7 (8.2) 30.7 (8.7) 0.63 (0.25) 0.50 (0.23) 116 (12) 69 (10) 71 (13)
t or χ2 −1.32 0.26 0.04 −1.70 −0.64 −0.93 −0.08 −1.06 −0.46 0.55 0.08 −0.84 1.89
p 0.18 0.61 0.95 0.09 0.53 0.35 0.94 0.30 0.65 0.59 0.93 0.41 0.06
BDI-II Beck Depression Inventory-2nd edition, STAI State Trait Anxiety Inventory, SBP systolic blood pressure, DBP diastolic blood pressure, BPM beats per minute
and chi-square analyses. 2-Group × 7-Time repeated measures analyses of variance (ANOVAs) were used to analyze the research questions. We report partial-eta2 (n2a) for ANOVA effect sizes, and significant main effects and interactions were decomposed using follow-up contrasts. Main effects for time were calculated to examine the impact of the experiment on blood pressure and heart rate from baseline to recovery, including the stressor. Time main effects were followed up by analyses of group × time interactions and tests of group differences. For the first research question on the effects of brief mindfulness training on blood pressure and heart rate, follow-up contrasts were conducted to examine differences immediately post-manipulation controlling for baseline. For the second research question on the effects brief mindfulness training on differences in cardiovascular reactivity to the PASAT, follow-up contrasts were conducted to examine differences from baseline to the beginning of the PASAT and from the beginning of the PASAT to the end of the PASAT. For the third research question on the effects of brief mindfulness training on cardiovascular recovery after the end of the stressor, follow-up contrasts were conducted to examine differences from baseline to the first recovery period (10 min) and to the second recovery period (20 min).
Results We examined whether brief mindfulness training would improve performance on the PASAT and if state anxiety would be related to worse performance on the PASAT. There were no between-group differences on state anxiety post-stressor or
PASAT performance (see Table 1). There was a significant main effect of time for PASAT performance with the average score decreasing from the first trial to the last trial, F(1,59)= 38.40, p
