Mindfulness DOI 10.1007/s12671-017-0793-z
ORIGINAL PAPER
Mindfulness Training, Yoga, or Both? Dismantling the Active Components of a Mindfulness-Based Stress Reduction Intervention Melissa Hunt 1 & Farah Al-Braiki 1 & Shannon Dailey 1 & Rachel Russell 1 & Krystyna Simon 1
# Springer Science+Business Media, LLC 2017
Abstract Mindfulness-based stress reduction (MBSR) can help college students cope effectively with stress, reducing negative affect in the short term and resulting in higher (more adaptive) heart rate variability (HRV). However, HRV is a measure of cardiovascular fitness, as well as parasympathetic control of the stress response. MBSR is a multicomponent intervention and it is unclear to what extent movement, including gentle yoga, mindfulness training, or the synergy between the two, has an impact on emotional and physiological outcomes. The current study dismantled yoga and explicit mindfulness training in a brief stress reduction intervention in college students. Participants were randomly assigned to either mindfulness training and meditation alone (no movement); yoga alone (no explicit mindfulness training); combined yoga and mindfulness training and meditation; an active placebo control consisting of study breaks with party games, access to a therapy dog, and healthful snacks; or a no-treatment control. All active treatments resulted in decreases in anxiety and dysphoria over the 4 weeks of treatment relative to the notreatment control, although by week 4, only the combined and yoga groups were significantly different from the control group on both measures. The no-treatment control group showed the lowest HRV at rest and during the challenge. The combined and yoga groups showed the highest HRV at rest, followed by moderate declines in HRV during the challenge, suggesting adaptive vagal withdrawal. The mindfulness training alone group was the only group to show no decrease
* Melissa Hunt
[email protected]
1
Department of Psychology, University of Pennsylvania, 425 South University Avenue, Philadelphia, PA 19104, USA
in HRV during the challenge, suggesting that they were the least stressed by the challenge. Keywords Mindfulness . Stress management . Yoga . Anxiety . Heart rate variability . Meditation
Introduction College students often rank stress as the number 1 health impediment to academic performance (American College Health Association 2008) and a significant factor in overall wellbeing (Brougham et al. 2009). Historically, approximately 75% of college students have reported at least moderate stress, with another 10% reporting serious stress (Abousiere 1994). Over a span of 10 years, longitudinal studies have revealed a nationwide decline in both physical and psychological health among college students, coupled with increasing trends in perceived stress levels (Sax 1997). Students today often feel overwhelmed by stress (Kadison and DiGeronimo 2004). Moreover, high levels of stress have been shown to be harmful both to overall health (Hudd et al. 2000), as well as academic success (Struthers et al. 2000). Academic stress is exacerbated by poor time management skills (Misra and McKean 2000) and by maladaptive coping strategies such as smoking, drugs, and alcohol (Pritchard et al. 2007). Brougham et at. (2009) advocated the use of adaptive emotion-focused strategies in stress reduction interventions, since both male and female college students tend to rely on emotion-focused coping strategies . A number of relatively brief adaptive stress management interventions have been developed and tested in university students in the last 15 years. For example, Deckro et al. (2002) compared a six-session cognitive-behavioral and relaxation skills stress management intervention to a no-treatment
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control. They found significant reductions in self-reported distress, anxiety, and perceived stress. Mindfulness-based interventions have been a particularly fruitful avenue of research in this area. For example, Rosenzweig et al. (2003) found that a 10-week mindfulness-based stress reduction (MBSR) program, compared to a didactic seminar on complementary medicine, led to reductions in self-reported distress in medical students. Jain et al. (2007) compared mindfulness meditation to relaxation training and a no-treatment control. They found that brief training in both mindfulness and somatic relaxation (a combination of deep breathing and progressive muscle relaxation) led to reductions in self-reported distress while meditation also reduced rumination. While such studies are promising, they typically rely entirely on self-report measures and often do not include credible placebo control conditions. Indeed, in a meta-analysis of the impact of MBSR programs on healthy people, Chiesa and Serretti (2009) found that MBSR typically results in non-specific effects on stress reduction in comparison to inactive control conditions, but few specific effects compared to interventions designed to be structurally equivalent to the meditation program. In response to the concerns raised in the mindfulness literature about the lack of credible control conditions and the reliance on self-report measures, Shearer et al. (2015) investigated the efficacy of a brief (four-session) MBSR-type intervention compared to a credible and ecologically valid placebo control (a pleasant group study break with access to a therapy dog and healthful snacks) and to a no-treatment control. Moreover, they not only included self-report measures of mood and distress but also obtained a physiological measure of stress reactivity and emotion regulation (heart rate variability (HRV)) captured during a cognitive stress challenge several weeks after the intervention. HRV reflects the balance of parasympathetic and sympathetic nervous system activity and is an index of regulated emotional responding (Appelhans and Luecken 2006; Thayer et al. 2009). HRV has been linked to both cardiovascular and mental health (Thayer et al. 2012). Numerous studies have found an inverse relationship between HRV and perceived stress (e.g., Dishman et al. 2000). In general, higher HRV scores indicate reduced stress and/or better stress management and coping. Moreover, mindfulness training and meditation have been associated with higher HRV (e.g., Burg et al. 2012; Krygier et al. 2013), as has the practice of yoga (e.g., Pal 2015). Shearer et al. (2015) argued that HRV was a particularly useful way of objectively assessing the impact of various behavioral interventions on stress management and emotion regulation. Their results seemed to bear out both the usefulness and the specificity of MBSR-type interventions in building stress management skills over and above active placebo control interventions. They found that by the end of the fourth session, those in the MBSR group exhibited significantly lower state
anxiety compared with those in the other groups, while the dog group was also significantly less anxious than the notreatment group. In addition, both the dog and the MBSR groups exhibited significantly less dysphoric affect than the control group. In other words, the credible placebo control resulted in almost equivalent reductions in negative affect acutely. All of the participants then came in for a post-treatment assessment during which they were given a cognitive stressor challenge (selected subtests of the WAIS-IV IQ test) (Wechsler 2008). Electro-cardiogram data were collected during the cognitive challenge to assess HRV. Participants in the MBSR group exhibited significantly higher HRV during the cognitive challenge than those in the other two groups, signifying a greater ability to downregulate the stress response. Individuals in the dog group, meanwhile, were no different from control participants. These results suggest that a brief MBSR style intervention might be able to help college students learn to cope more adaptively with academic stress, whereas study breaks (even with a therapy dog), while fun and relaxing in the moment, confer no long-term benefits from skill learning. One difficulty in interpreting the results from Shearer et al. (2015), however, is that MBSR-type programs (Kabat-Zinn and Hanh 2009), including the intervention used in that study, involve mindful movement (e.g., walking exercises) and light yoga. Because MBSR incorporates both mindfulness meditation and mindful movement, it is considered a multicomponent program. Mindfulness meditation per se is only one component of a number of adaptive stress coping strategies involved in MBSR-type interventions. Indeed, in another meta-analysis of the effects of mindfulness meditation, Eberth and Sedlmeier (2012) found that while multicomponent MBSR programs generally have powerful effects on overall psychological well-being, pure mindfulness meditation studies show the largest effects only on variables associated with the concept of mindfulness itself, typically measured by self-report. They questioned whether some of the effect sizes found for MBSR might be partly inflated by effects that are not attributable to its mindfulness meditation component. Of particular concern in interpreting the findings of Shearer et al. (2015) is that HRV is a measure of cardiovascular fitness and is significantly impacted by exercise (Sandercock et al. 2005). It is possible that the HRV results in their study were due to the physical movement/exercise component of the program, and not to the mindfulness aspects at all. Finally, only one other study that we know of has attempted to examine the relative effects of specific MBSR activities (including yoga, sitting and informal meditations, and body scan meditation) on various outcome measures. Gallegos et al. (2013) did not dismantle a standard 8-week MBSR intervention in older adults, but they did measure how much of each practice participants engaged in. They found that more yoga
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practice was associated with higher post-treatment insulin-like growth factor (IGF-1) and positive affect, while sitting meditation was associated with improved IGF-1, but not positive affect and body scans were only associated weakly with reduced antigen-specific immunoglobulin (IgM). In contrast, the current dismantling study attempted to disentangle the contributions of mindfulness training and meditation (with no movement or physical exercise component) and yoga (stripped of its explicit mindfulness and selfcompassion components), compared to a full multicomponent MBSR treatment, a credible placebo control, similar to the one used by Shearer et al. (2015), and a no-treatment control. Relevant outcome measures included self-reported anxiety and dysphoric affect, and heart rate variability both during a resting baseline and a stressful cognitive challenge.
Method Participants Participants consisted of undergraduate students at a selective, private, East Coast University enrolled in psychology courses. Subjects enrolled through a department-wide online experiment scheduling system and received class credit in return for their participation. Upon signing up for the experiment, participants completed a baseline assessment battery (described in further detail below), which included the Beck Depression Inventory (BDI). We eliminated BDI item number 9 regarding suicidal thoughts or wishes, and used a score above 23 as an exclusion criterion. Higher scores indicate moderate to severe levels of depression in subjects. None of the interventions being employed were meant to be clinical interventions, and we would not expect them to have a significant effect on clinically depressed individuals. Randomization was accomplished by rolling a die. In the first phase of the experiment, 60 subjects enrolled and 57 completed the post-intervention stress challenge. Twelve subjects were randomized to the combined mindfulness training, meditation, and yoga group; 11 to the mindfulness training and meditation group; 11 to the yoga group; 14 to the dog group; and 12 to the no-treatment control group. In this phase of the experiment, eight participants overall missed a session and did not complete the weekly mood inventory. In the second phase, 59 subjects enrolled and 53 completed the post-intervention stress challenge. Ten were randomized to the combined mindfulness training, meditation, and yoga group; 12 to the mindfulness training and meditation group; 13 to the yoga group; 12 to the dog group; and 12 to the no-treatment control group. In this phase of the experiment, eight participants missed a session and did not complete the weekly mood inventory. Overall, 74% of the participants identified as female, and 26% as male. Subjects had to be at least 18 years
old to participate, and the mean age of participants was 19.3 years. The subjects self-identified as 52% non-Hispanic white, 27% as Asian or Asian-American, 9% as Hispanic or Latino, 5% as black or African-American, 4% as multiracial, 2% as Indian, and 1% as Arab. Procedure The weekend prior to the first session, subjects were consented electronically and completed the baseline assessment battery, including demographics, the BDI, the Positive and Negative Affect Scale (PANAS), and the state version of the Spielberger State/Trait Anxiety Inventory (STAI). The group sessions in the first phase of the experiment were held on the same day of the week at the same time. In the second phase, the mindfulness, yoga, and dog study break sessions were held on one day at the same time, while the combined group’s sessions were held on the same day an hour later. Mindfulness Training Alone The mindfulness training group’s session was held in a large carpeted room. Subjects were briefly educated in the first session on the background and usefulness of mindfulness, diaphragmatic breathing, and the physiological and psychological effects of stress. The remainder of the first session and all the subsequent sessions focused on experiential mindfulness exercises and practice (via spoken scripts or audio recordings) derived from the MBSR program created at the University of Massachusetts by John Kabat-Zinn (Kabat-Zinn and Hanh 2009). However, no mindful movement was employed—eliminating common mindfulness practices such as mindful walking, stretching, and light yoga. The intervention included the other standard components of MBSR, including mindful breathing, body scans, mindful listening, mindful eating, loving kindness meditations, and meditations on stress and anxiety. The overall emphasis was on cultivating a present-focused, nonjudgmental awareness of one’s body sensations, thoughts, and emotions and incorporating mindfulness into everyday aspects of one’s life. The importance of self-compassion and a nonjudgmental attitude toward one’s own beliefs, feelings, and thoughts was highlighted throughout. Exercises progressed from those emphasizing attention control (e.g., eating and breathing meditations) to those encouraging emotion regulation and self-awareness (e.g., self-compassion and open monitoring meditations) (Tang et al. 2015). Participants were encouraged to practice the breathing and mindfulness techniques outside of the sessions in order to develop the skill of mindfulness. Yoga Alone The yoga group’s session was held in a large carpeted room and participants were provided yoga mats and blocks. Subjects were initially taught diaphragmatic breathing, and the importance of attention to the rhythm of breath was emphasized throughout all four sessions. Breath awareness is
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an essential component of every formal yoga practice (the Bfourth limb^ of yoga or pranayama). Throughout the session, subjects were guided through traditional yoga poses (asanas) that focused on developing balance, core strength, and flexibility, followed by relaxed breathing. Explicit focus on traditional aspects of yoga that emphasize self-acceptance and mindful awareness including niyamas (contentment), pratyahara (withdrawal of the senses), dharana (concentration), dhyana (meditation), and Samadhi (merging with the divine) were excluded from this intervention, and no instruction or guidance was provided during the final relaxed breathing exercise (shavasana). Group leaders did not explicitly encourage mindful self-compassion. Instead, the group leader simply modeled the Bright^ way to do each pose and then corrected participants. Participants in this group were also encouraged to practice breathing and the yoga poses outside of the sessions. Multicomponent Mindfulness Training and Yoga The combined yoga and mindfulness training group most closely resembled both the traditional practice of yoga and multicomponent MBSR. These sessions were held in a large room and participants were again provided yoga mats and blocks. As in the mindfulness training alone group, subjects were briefly educated on the practice of mindfulness, diaphragmatic breathing, and the physiological and psychological effects of stress. For the remainder of session 1 and all of the subsequent sessions, subjects were guided through a number of experiential mindfulness exercises derived from the MBSR program. The intervention consisted of breathing exercises, traditional yoga poses (asanas) that focused on developing balance, core strength, and flexibility, and short, focused mindfulness exercises including breathing, body scans, mindful listening, mindful eating, loving kindness meditations, and meditations on stress and anxiety. In this group, the group leaders did explicitly encourage mindful self-compassion during the yoga asanas by saying things like Bmeet your body where it is today^ or Bbe aware of the messages your body is sending you—don’t force the pose^ or Bthis isn’t about who can do the pose the best or even about getting better—just inhabit whatever variant of the pose you need today non-judgmentally in this moment.^ Throughout, there was an emphasis on incorporating mindfulness into everyday activities and cultivating a present focused, nonjudgmental attitude toward one’s own sensations, experiences, beliefs, feelings, and thoughts. Study Break with a Therapy Dog For the study break group, participants gathered in an undergraduate lounge and were provided snacks and the company of a large, friendly golden retriever who frequently visits campus as a therapy dog. Subjects were encouraged to interact with the dog and each other. Each week, they were led in various icebreaker or interactive games, including charades and telephone, and were allowed to socialize freely, play with the dog, and eat healthful snacks.
After each session, participants in each of the four active treatment groups completed paper-based versions of the mood inventories. Subjects who were encouraged to practice particular skills also reported the number of times they practiced in between sessions. Participants in the no-treatment control group were e-mailed links to the mood inventory after each session was over, and they were asked to complete the survey within 3 h. One to 3 weeks after the final session, each participant came to the lab and was administered four subtests of the WAIS-IV IQ test (Block Design, Similarities, Matrix Reasoning, and Arithmetic) (Wechsler 2008). The WAIS is a challenging cognitive assessment that requires minimal feedback during standardized administration. For those who value intelligence and their own intellectual capacity, the test can be very stressful. In order to enhance the stressful environment somewhat and communicate the seriousness of the test, assessors, who were unknown to the subjects and also blind to subjects’ group assignment, dressed in lab coats and maintained a stern and standoffish demeanor. Test administrators also continued subtests beyond the standard stop point that occurs once a participant has made a particular number of incorrect responses, in order to prolong the experience and the stressful conditions of the test. Furthermore, subjects were informed that after the administration of the test and the subject’s completion of the assessment battery, they would be given their scores for the IQ test. Administration of this test was selected as a non-deceptive stress challenge, meant to imitate a typical stressful situation (evaluative testing) in the everyday lives of college students. Prior to the administration of the WAIS, the emWave Pro device was attached to the subject’s ear lobe and baseline heart rate data was collected for 5 minutes. During these 5 minutes, the assessor left the room and instructed the subjects to do their best to relax and that they were free to use any skills they might have learned from their respective intervention. Heart rate continued to be collected throughout the rest of the test. After the WAIS, subjects were brought to another room to complete the follow-up assessment battery (STAI, PANAS, BDI), while the assessor calculated their score. Upon completion, subjects were debriefed, given their scores (and informed that the scores were an inaccurate measure of IQ, given the testing conditions), and given course credit. All of these steps were repeated for the second phase of the experiment; except in the second phase, leaders of the intervention groups were counterbalanced across different interventions to control for possible experimenter effects. Measures State Anxiety Inventory for Adults (STAI; Spielberger et al. 1970). The mood inventory consisted of the 20-item state anxiety subscale of the STAI. The STAI has an alpha reliability
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coefficient of 0.92 (Spielberger & Gorsuch 1983) and assesses psychological stress and arousal on a four-point Likert scale. Positive and Negative Affect Schedule (PANAS; Watson et al. 1988). The PANAS consists of 20 words describing different feelings or emotions. Items can be divided into a positive affect score and a negative affect score on a fivepoint Likert scale. On the timescale of a week, the positive affect scale and the negative affect scale both have an alpha coefficient of 0.87 (Watson et al. 1988). Beck Depression Inventory (BDI-II; Beck et al. 1996). The BDI contains 21 items assessing symptoms associated with depression, and has an alpha coefficient of 0.81 for nonpsychiatric patients (Beck et al. 1988). For the purposes of this study, we excluded item number 9 of the BDI related to suicidal ideation.
for drift. Our final ranges of heart rate variability were 26 to 107 at baseline and 26 to 87 during the challenge, which are comparable to the range of normative SDNN values reported by Nunan et al. (2010). Once the raw EKG data were converted to usable HRV, those data were entered along with all demographic and self-report data into SPSS v.18.
Results There were no significant group differences in any of our measures at baseline: depressive symptoms, anxious arousal, or dysphoric affect. Additionally, there were no significant effects of sex or race on any of our measures: anxious arousal, dysphoric affect, average heart rate (baseline and challenge), and heart rate variability (baseline and challenge).
Heart Rate Variability Mood Measures
Data Analyses Analysis of the HRV data involved using a program called gHRV to manually eliminate obvious artifacts: data points outside of the biological range of 50 to 200 beats per minute. For our data analysis, we used the strong artifact correction option in Kubios, which uses a threshold of 0.05 s to define abnormal deviation from the local mean RR interval. RR intervals selected by this criterion were corrected by a piecewise cubic spline interpolation method (Tarvainen and Niskanen 2012). We also used the smoothin prior option to account
All four active treatment groups experienced significant decreases in anxious arousal from baseline over the four treatment sessions compared to the no-treatment control. The repeated measure ANOVA of treatment condition on STAI across five time points from baseline and after each treatment session was significant [F(4,86) = 2.75, p < 0.05]. Pairwise comparisons showed that the mindfulness, yoga, and combined groups were all significantly different from the notreatment control group (all p < 0.05), but not from each other, while the dog group was only marginally significantly different from the control group by session 4 (p = 0.07; see Fig. 1). There was also a significant effect of condition on change in dysphoric affect. The repeated measure ANOVA of treatment condition on negative affect on the PANAS across five time points from baseline and after each treatment session was significant [F(4,87) = 2.78, p < 0.05]. Pairwise comparisons showed that the no-treatment control group reported significantly more dysphoric affect over time than the dog, yoga, and combined groups (all p ≤ 0.01), although they were not Anxious Arousal Over Time by Condition
50 Mean STAI Score
Heart rate data was collected using the emWave Pro® and analyzed using Kubios HRV version 2.1 developed by the Biosignal Analysis and Medical Imaging Group at the Department of Applied Physics, University of Eastern Finland, Kuopio, Finland. Participants clipped the emWave Pro sensor to their ear lobe, where it remained during a baseline resting period and throughout the administration of the cognitive challenge. The recommended measure of HRV is the SDNN, or the standard deviation of the NN (normal-to-normal) intervals (Task Force 1996). A systematic review of 27 studies concerning SDNN values from short-term HRV analysis found a mean SDNN value of 50 ms, a median value of 51 ms, and a range of 32–93 ms (Nunan et al. 2010). Accurate HRV analysis however can be challenging due to errors in heart rate data collection from either technical or physiological artifacts. Our procedures introduced some technical artifacts due to necessary hand and arm movement for the Block Design subtest of the WAIS (see below). Participants were instructed to minimize unnecessary movement as much as possible, but inevitably, there was still some occasional movement throughout the rest of the WAIS administration.
45 40
Combined
35
Control
30
Dog
25
Meditation
20
Fig. 1 Anxious arousal over time by condition
Yoga
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significantly different from the mindfulness and dog groups by session 4 (see Fig. 2). There were no significant between group differences on positive affect or depression scores over time. After the stress challenge, there was no overall significant effect of condition on either self-reported anxiety or negative affect. However, planned comparisons revealed that the participants in the dog group actually reported significantly more anxious arousal than participants in the combined and notreatment control groups (both p < 0.05) and marginally more anxiety than those in the mindfulness group (p = 0.08). Similarly, those in the dog group reported marginally more negative affect than those in the combined, yoga, and notreatment control groups (all p < 0.10). Treatment Adherence We had two possible measures of treatment adherence—attendance at each scheduled session and self-reported practice of the skills taught in the three skills-based groups. There were no significant differences in attendance across groups. Among the three skills-based groups, there was a trend toward condition being associated with self-reported practice [F(2,66) = 1.92, p = 0.15]. Planned comparisons revealed that the combined group reported marginally significantly more practice than the yoga alone group. However, practice did not moderate any of the outcomes. Physiological Measures There were no significant differences in heart rate by condition at follow-up baseline, prior to the cognitive challenge, nor were there any significant effects of condition on change in HR from baseline to challenge. There were significant differences in HRV at pre-challenge resting baseline, however [F(4,103) = 3.42, p = 0.01] with the combined and yoga groups showing the highest HRV, followed by the dog and mindfulness groups, with the control group
showing the lowest HRV. There were also significant group d i ff e r e n c e s i n H RV d u r i n g t h e s t r e s s c h a l l e n g e [F(4,103) = 2.68, p < 0.05]. Pairwise comparisons revealed that the control group showed the lowest HRV overall, while the other groups were not significantly different from each other. That is, all the active treatment groups ended up with similar HRV during the challenge. However, examining the slope of change from resting baseline to challenge revealed an interesting pattern. The combined and yoga groups both showed significant decreases in HRV from unusual highs at baseline to means that would be considered average baseline HRV during the challenge [t(18) = 4.08, p = 0.001 and t(20) = 4.15, p < 0.001, respectively]. The control group started at a low average baseline and came down only modestly and non-significantly [t(20) = 1.38, ns]. The dog group started at a normal baseline and came down modestly, but significantly during the challenge [t(21) = 2.36, p < 0.05]. The mindfulness group was the only group to show no decrease in HRV at all during the challenge [t(21) = −0.76, p = 0.46] (see Fig. 3).
Discussion This study attempted to dismantle the active components of MBSR and compared the relative benefits of mindfulness training and meditation with no movement, yoga with no explicit mindfulness component, and the full, combined MBSR treatment and compared all three to an active, credible placebo control and a no-treatment control. We found that all four active treatments generally resulted in significant decreases in self-reported anxiety and dysphoric affect over the course of treatment relative to the no-treatment control, although the effects started to attenuate for both the mindfulness alone and the dog groups by week 4 of the intervention. Several weeks later, all participants returned to the lab to assess resting or baseline HRV and to undergo a stressful cognitive challenge. We found that the two groups involving yoga
23 21 19 17 15 13 11 9 7 5
HRV at Baseline and Challenge by Condition
70 65
Combined Control Dog Meditation Yoga
Mean SDNN
Mean NA Score
Negative Affect Over Time by Condition
Control
55
Dog
50
Meditation
45
Yoga
40 Fig. 2 Negative affect over time by condition
Combined
60
Resting
Challenge
Fig. 3 Heart rate variability at rest and challenge
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(the combined group and the yoga alone group) were indistinguishable from each other with respect to HRV results. Moreover, both groups showed significantly higher HRV at resting baseline than the other groups and showed equal, adaptive vagal withdrawal during the challenge. Moderate vagal withdrawal has been shown to be associated with optimal performance on executive function tasks (Marcovitch et al. 2010) and to be associated with adaptive functioning across a range of cognitive and social challenges (Graziano and Derefinko 2013). While the decrease in HRV was significant for both groups, it is important to note that they ended up at a relatively robust mean SDNN of 50–51 ms, similar to the results of the MBSR group from Shearer et al. (2015). It is worth noting that the HRV results cannot be attributed simply to changes in breath awareness or deep breathing. Breath awareness and deep diaphragmatic breathing were taught in all three of the MBSR component conditions. Nevertheless, the HRV results at follow-up baseline were significantly different for the mindfulness training alone group than for the two groups that involved yoga. These results suggest that there is something particularly powerful about yoga (whether or not it is presented as a part of a multicomponent, mindfully focused intervention) that has salutary effects on cardiac vagal control and the stress response. As expected, the control group showed the lowest HRV at both resting baseline and during the cognitive challenge, replicating the results of Shearer et al. (2015). Interestingly, the dog group did a bit better with respect to HRV than the comparable group in Shearer et al. (2015). Although the dog group reported marginally elevated anxiety and negative affect after the challenge relative to the other four groups, they were not significantly different in HRV from the mindfulness training alone group at resting baseline, nor were they significantly different from any of the other active treatment groups during the challenge. These results were somewhat surprising at first. Why would the dog group have reported marginally more distress about the challenge than the other groups? We attribute this in part to having structured the dog group somewhat differently from Shearer et al. (2015), and to a strong contrast effect. In our study, the group leader took a much more active role in organizing social activities and ice breaker games as well as activities that allowed everyone to interact with the dog. During this intervention, participants in the dog group were welcomed into a joyful environment where time was spent playing games with each other and with a loving golden retriever. Anecdotally, the participants enjoyed the group enormously and found that it allowed significant opportunities for social connection. Many people were sad when the group ended. Most exchanged contact information with each other, and many took cell phone pictures of the dog. It is possible that a cohesive, structured social group experience may have increased social support, sense of belonging, and community, advantages that might well have persisted beyond the
intervention itself and that contribute to well-being in undergraduates (Kase et al. 2016). During the challenge session, however, these participants were suddenly placed in a stressful situation with a cold, unknown experimenter and no dog. The contrast to what they had experienced earlier could account for the uptick in self-reported distress, while the lingering benefits of social support and social cohesion might account for the greater sympathovagal regulation in the face of that distress. In many ways, the mindfulness training alone group was the most interesting. They showed HRV at resting baseline above the control group, comparable to the dog group, and significantly below the combined and yoga alone groups. But they were also the only group to show a modest (though nonsignificant) increase in HRV during the cognitive challenge. That is, they seemed to be the group least troubled by the stressor. This raises interesting questions about which intervention Bwon.^ Is it better to have higher resting baseline HRV and then Brise to the challenge^ in moments of stress with adaptive vagal withdrawal (a rather Western philosophy)? Or is it better to have moderate resting baseline HRV and remain unruffled and apparently unconcerned in moments of challenge (a rather Eastern approach)? These results also raise interesting questions about the power of yoga over and above the power of explicit mindfulness training interventions. Across most of our outcomes, the yoga and the combined yoga and mindfulness training groups were statistically similar to each other, while the mindfulness training alone group was different. The combined treatment group did seem to have a slight edge on several outcome measures, and anecdotally, participants seemed to enjoy that group more than either the yoga alone or the mindfulness training alone groups. In terms of adherence, the combined group did report practicing the skills marginally significantly more than the yoga alone group. In private, the research team often referred to the yoga alone group as the Bjudgmental^ or Bbad gym^ yoga group. We deemed it unlikely that participants in that group would have continued to come had the intervention been offered longer or had it not been a way to fulfill a research requirement. In retrospect, we wish we had included a formal measure of treatment acceptability. Despite these factors, the explicit mindfulness, self-acceptance, and self-compassion exercises in the combined group do not seem to have conferred much additive benefit. Only a longer study, with more diverse outcome measures will allow us to address questions relevant to treatment adherence, acceptability, and long-term benefits. In sum, MBSR interventions include a number of active components. This study attempted to dismantle the relative contributions of mindfulness training and meditation alone (with no movement), yoga alone (with no explicit mindfulness), and their combination. We found that yoga alone was
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comparable to the full combined intervention on a number of outcome measures, including self-reported distress and physiological stress regulation both at resting baseline and in response to a challenge. Future studies should attempt to discover whether the benefits of yoga are attributable to the physical exercise itself, or to some other component embedded in the practice. In the meantime, it would seem wise to include plenty of mindful movement in stress reduction interventions aimed at college students. Author Contributions MH: designed the study, trained the other authors in the MBSR component interventions, analyzed the data, and wrote the paper. FA and SD: helped design the study; implemented the MBSR component interventions; helped enter, clean, and analyze the data; and collaborated in writing the paper. RR: helped design the mindfulness intervention, helped implement the interventions, helped enter and clean the self-report data, and cleaned and analyzed the HRV data. KS: helped design the placebo control intervention, helped implement the interventions, helped enter and clean the self-report data, and cleaned and analyzed the HRV data. Both RR and KS also collaborated in editing the final MS. Compliance with Ethical Standards Ethical Approval All procedures performed in the study involving human participants were in accordance with the ethical standards of the institutional review board at the university where the research was carried out and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed Consent Informed consent was obtained from all individual participants included in the study. Conflict of Interest The authors declare that they have no conflict of interest.
References Abousiere, R. (1994). Sources and levels of stress in relation to locus of control and self esteem in university students. Educational Psychology, 14(3), 323–330. American College Health Association. (2008). National college health assessment spring 2007 reference group data report (abridged). Journal of American College Health, 56(5), 469–479. Appelhans, B. M., & Luecken, L. J. (2006). Heart rate variability as an index of regulated emotional responding. Review of General Psychology, 10, 229–240. Beck, A. T., Steer, R. A., & Garbin, M. G. (1988). Psychometric properties of the Beck Depression Inventory: twenty-five years of evaluation. Clinical Psychology Review, 8(1), 77–100. Beck, A. T., Steer, R. A., & Brown, G. K. (1996). Manual for the Beck Depression Inventory (2nd ed.). San Antonio, TX: Psychological Corporation, Harcourt, Brace. Brougham, R. R., Zail, C. M., Mendoza, C. M., & Miller, J. R. (2009). Stress, sex differences, and coping strategies among college students. Current Psychology, 28, 85–97. Burg, J. M., Wolf, O. T., & Michalak, J. (2012). Mindfulness as selfregulated attention. Swiss Journal of Psychology, 71, 135–139. Chiesa, A., & Serretti, A. (2009). Mindfulness-based stress reduction for stress management in healthy people: a review and meta-analysis.
The Journal of Alternative and Complementary Medicine, 15(5), 593–600. Deckro, G. R., Ballinger, K. M., Hoyt, M., Wilcher, M., Dusek, J., Myers, P., et al. (2002). The evaluation of a mind/body intervention to reduce psychological distress and perceived stress in college students. Journal of American College Health, 50(6), 281–287. Dishman, R. K., Nakamura, Y., Garcia, M. E., Thompson, R. W., Dunn, A. L., & Blair, S. N. (2000). Heart rate variability, trait anxiety, and perceived stress among physically fit men and women. International Journal of Psychophysiology, 37(2), 121–133. Eberth, J., & Sedlmeier, P. (2012). The effects of mindfulness meditation: a meta-analysis. Mindfulness, 3(3), 174–189. Gallegos, A. M., Hoerger, M., Talbot, N. L., Krasner, M. S., Knight, J. M., Moynihan, J. A., & Duberstein, P. R. (2013). Toward identifying the effects of the specific components of mindfulness-based stress reduction on biologic and emotional outcomes among older adults. The Journal of Alternative and Complementary Medicine, 19(10), 787–792. Graziano, P., & Derefinko, K. (2013). Cardiac vagal control and children’s adaptive functioning: a meta-analysis. Biological Psychology, 94(1), 22–37. Hudd, S. S., Dumlao, J., Erdmann-Sager, D., Murray, D., Phan, E., Soukas, N., & Yokozuka, N. (2000). Stress at college: effects on health habits, health status and self-esteem. College Student Journal, 34(2), 217–228. Jain, S., Shapiro, S. L., Swanick, S., Roesch, S. C., Mills, P. J., et al. (2007). A randomized controlled trial of mindfulness meditation versus relaxation training: effects on distress, positive states of mind, rumination, and distraction. Annals of Behavioral Medicine, 33(1), 11–21. Kabat-Zinn, J., & Hanh, T. N. (2009). Full catastrophe living: using the wisdom of your body and mind to face stress, pain, and illness. New York: Delta. Kadison, R., & DiGeronimo, T. F. (2004). College of the overwhelmed: the campus mental health crisis and what to do about it. San Francisco: Jossey-Bass. Kase, C., Rivera, N., & Hunt, M. (2016). The psychological effects of sorority recruitment: a question of self-selection. Oracle: The Research Journal of the Association of Fraternity/Sorority Advisors, 11(1), 1–16. Krygier, J. R., Heathers, J. A., Shahrestani, S., Abbott, M., Gross, J. J., & Kemp, A. H. (2013). Mindfulness meditation, well-being, and heart rate variability: a preliminary investigation into the impact of intensi ve Vi pass ana m edit ati on. I nt er na t io na l Jo ur n al of Psychophysiology, 89(3), 305–313. Marcovitch, S., Leigh, J., Calkins, S. D., Leerks, E. M., O’Brien, M., & Blankson, A. N. (2010). Moderate vagal withdrawal in 3.5-year-old children is associated with optimal performance on executive function tasks. Developmental Psychobiology, 52(6), 603–608. Misra, R., & McKean, M. (2000). College students’ academic stress and its relation to their anxiety, time management, and leisure satisfaction. American Journal of Health Studies, 16(1), 41–51. Nunan, D., Sandercock, G. R., & Brodie, D. A. (2010). A quantitative systematic review of normal values for short-term heart rate variability in healthy adults. Pacing and Clinical Electrophysiology, 33(11), 1407–1417. Pal, G. K. (2015). Yoga and heart rate variability. International Journal of Clinical and Experimental Physiology, 2(1), 2. Pritchard, M. E., Wilson, G. S., & Yamnitz, B. (2007). What predicts adjustment among college students? A longitudinal panel study. Journal of American College Health, 56(1), 15–22. Rosenzweig, S., Reibel, D. K., Greeson, J. M., Brainard, G. C., & Hojat, M. (2003). Mindfulness-based stress reduction lowers psychological distress in medical students. Teaching and Learning in Medicine, 15(2), 88–92.
Mindfulness Sandercock, G. R., Bromley, P. D., & Brodie, D. A. (2005). Effects of exercise on heart rate variability: inferences from meta-analysis. Medicine and Science in Sports and Exercise, 37(3), 433–439. Sax, L. J. (1997). Health trends among college freshmen. Journal of American College Health, 45(6), 252–262. Shearer, A., Hunt, M., Chowdhury, M., & Nicol, L. (2015). Effects of a brief mindfulness meditation intervention on student stress and heart rate variability. International Journal of Stress Management. Advance online publication. doi:https://doi.org/10.1037/a0039814. Spielberger, C.D., & Gorsuch, R.L. (1983). Manual for the State-Trait Anxiety Inventory (Form Y) ("Self-Evaluation Questionnaire). Palo Alto: Consulting Psychologists Press. Spielberger, C. D., Gorsuch, R. L., & Lushene, R. E. (1970). STAI: manual for the State-Trait Anxiety Inventory. Palo Alto: Consulting Psychologists Press. Struthers, C. W., Perry, R. P., & Menec, V. H. (2000). An examination of the relationship among academic stress, coping, motivation and performance in college. Research in Higher Education, 41(5), 581– 592. Tang, Y., Hölzel, B. K., & Posner, M. I. (2015). The neuroscience of mindfulness meditation. Nature Reviews Neuroscience, 16(4), 213–225.
Tarvainen, M. P., & Niskanen, J. (2012). Kubios HRV version 2.1 user’s guide. Finland: University of Eastern Finland. Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology. (1996). Heart rate variability: standards of measurement, physiological interpretation and clinical use. Circulation, 93, 1043–1065. Thayer, J. F., Hansen, A. L., Saus-Rose, E., & Johnsen, B. H. (2009). Heart rate variability, prefrontal neural function, and cognitive performance: the neurovisceral integration perspective on self-regulation, adaptation, and health. Annals of Behavioral Medicine, 37(2), 141–153. Thayer, J. F., Åhs, F., Fredrikson, M., Sollers, J. J., & Wager, T. D. (2012). A meta-analysis of heart rate variability and neuroimaging studies: implications for heart rate variability as a marker of stress and health. Neuroscience & Biobehavioral Reviews, 36(2), 747–756. Watson, D., Clark, L. A., & Tellegen, A. (1988). Development and validation of brief measures of positive and negative affect: the PANAS scales. Journal of Personality and Social Psychology, 54(6), 1063. Wechsler, D. (2008). Wechsler Adult Intelligence Scale IV. San Antonio, TX: Harcourt Assessment Inc.
