Decentering from internal experiences has been identified as a potential mechanism of mindfulness (Segal et al., 2002
; Shapiro et al., 2006
). The present study compared the effects of brief practice of mindful breathing (MB), progressive muscle relaxation (PMR), and loving-kindness meditation (LKM) on decentering assessed by two methods. First, MB was found to produce higher scores on the decentering scale of the Toronto Mindfulness Scale (Lau et al., 2006
) than PMR and LKM. Second, we also operationalized decentering as a relatively weak correlation between frequency of repetitive thought (RT) and negative reactions to RT, suggesting an unlinking of repetitive thoughts and emotional reactivity to them. Consistent with predictions, there was a stronger association between frequency of RT and negative emotional reactions to them in the PMR and LKM conditions than in the MB condition. Decentering has been found to increase pre- to post-intervention in non-controlled clinical studies of mindfulness-based stress reduction (Carmody et al., 2009
; Lau et al., 2006
, Study 2). The present study complements and extends these studies with the inclusion of two active comparison conditions allowing the direct test of the effectiveness of mindful breathing to facilitating decentering relative to other stress management strategies.
The hypotheses regarding the effects of MB on frequency of RT and negative reaction to RT were partially supported in that participants in the MB condition reported greater frequency of RT but no difference in negative reaction to RT relative to participants in the PMR and LKM conditions. Each of these results is considered in turn.
One interpretation of the greater reported frequency of RT in the MB condition is that this exercise heightened awareness of repetitive thoughts relative to the other two conditions given that MB explicitly asks participants to notice when thoughts wander from breathing sensations. Nonetheless, this finding may appear to run counter to findings from clinical interventions that rumination tends to reduce following participation in multi-week mindfulness training interventions (Jain et al., 2007
; Kumar et al., 2008
; Ramel et al., 2004
). Taken together, however, these findings raise the intriguing possibility that reduction in ruminative thought processes during mindfulness training could be non-linear. Objectively attending to internal experience in mindfulness practice (i.e., “bare” attention) may initially heighten awareness of unpleasant repetitive thought but, consistent with the principles of exposure therapy, ultimately facilitate its decrease through habituation, distress tolerance, and emotional processing (see Baer, 2003
; A.M. Hayes & Feldman, 2004
; Linehan, 1993
; Shapiro et al., 2006
). Testing for the presence of such effects is beyond the design of the present study. Although such phenomena may not be apparent immediately following a single session of meditation; it may not necessarily require a full clinical intervention to be detectable. In a recent experiment (Low et al., 2008
), participants’ heart rate was monitored while completing a stressful writing task. Participants were randomly assigned to one of three conditions: evaluating the appropriateness of emotions, attending to emotions in a non-judgmental and accepting way (analogous to mindfulness- and acceptance-based interventions), or a control group. No group differences were observed in the initial session. However, the acceptance group showed less cardiovascular reactivity and more rapid recovery than the evaluative group when the task was repeated in a second testing session one-week later.
The lack of effect of MB on negative reaction to RT needs to be considered in the context of the significant interaction between frequency of RT and condition in predicting RT. These results suggest that for individuals experiencing relatively lower levels of RT during the exercise, differences in negative reaction to RT are not evident. However, among individuals experiencing relatively higher levels of RT, group differences are evident. As such, the effect of condition on negative reaction to RT appears to be most pronounced among individuals who experienced greater frequency of intrusive thoughts, which may speak to the question of which individuals who are most likely to benefit from mindful breathing relative to other stress management interventions. This finding may also have reflected the different objectives of the three stress management exercises. In the PMR and LKM conditions, participants followed specific instructions to release muscle tension and visualize individuals to wish them wellness, respectively. Therefore, participants in the PMR and LKM groups who experienced repetitive thoughts during the exercise may have been more likely to perceive them as annoying distractions because they were interrupting another intentional activity. In contrast, participants who practiced MB were encouraged to view thoughts with an attitude of non-judgment and gently return focus to observing breathing sensations, which may have allowed these individuals to be more accepting of RT when they arose. This possibility is bolstered by the result that MB resulted in greater self-reported decentering than the PMR and LKM conditions.
The present study helps contribute to a growing body of laboratory studies on mindfulness meditation by examining decentering as an outcome in a study with an experimental design and the use of two comparison groups consisting of credible stress management activities. Indeed, all three interventions reduced emotional arousal to a comparable degree as assessed by measures of change in negative affect. Such a finding helps to establish that mindfulness practice has benefits that cannot be attributed solely to relaxation effects common to other stress management procedures (Roemer & Orsillo, 2003
). Furthermore, the differential association of frequency and emotional reaction to RT remained significant when change in negative affect was statistically controlled, which helps to further rule out this alternative explanation.
The findings on the role of decentering is consistent with evidence emerging from clinical studies suggesting that mindfulness- and acceptance-based interventions can facilitate an ability to experience repetitive thoughts and emotions without becoming emotionally distressed by them. For instance, Bach and Hayes (2002)
compared a 4-session Acceptance and Commitment Therapy (ACT) intervention with treatment as usual (TAU) in a sample of inpatients with psychotic symptoms. At a 4 month follow-up assessment, relative to the TAU group, patients in the ACT group reported that their hallucinations and delusions were less believable and distressing and were less likely to be rehospitalized. The latter finding is especially striking given that the ACT group actually reported greater frequency of hallucinations and delusions at the follow-up assessment than the TAU group—a finding consistent with the increased RT found in the present study. Findings from other treatment studies suggest that interventions that include mindfulness training may weaken (i.e., unlink) the association between depression symptoms and alcohol cravings among individuals with substance use disorders (Bowen & Witkiewitz, 2009
) and facilitate patients with treatment resistant depression learning to attend to emotions without becoming overwhelmed by them (Feldman et al., 2009
). Taken together, these clinical studies suggest that interventions designed to cultivate mindfulness and acceptance may alter the way that individuals respond to negative thoughts and emotions, and potentially render them less upsetting.
The present study examined both an established, direct method of assessing decentering (decentering scale of the TMS) and a novel, indirect strategy (as captured by the “unlinking” of frequency and negative reaction to thoughts). Results suggested some convergence across methodologies in that decentering and negative reaction to thoughts were negatively correlated among participants in the MB condition. When frequency of repetitive thoughts was held constant, decentering was negatively and significantly correlated with negative reaction to thoughts in both the full sample and the MB condition. Furthermore, a marginally-significant 3-way interaction integrating both assessment strategies suggested a synergistic association in that decentering (TMS) appears to further moderate the effect of exercise type on the relationship between frequency of RT and negative reaction to RT. Results suggest that the “unlinking” of frequency of thoughts and negative reactions to them may be specific to individuals who both practiced MB and who experienced higher levels of decentering. Based on this finding, a fruitful area for future research would be to see whether the clinical effectiveness of mindfulness meditation may be better explained by a combination of contextual factors, including practice type and practice quality as identified in this study, in addition to practice frequency and duration as identified in previous work (for review see Vettese et al., 2009
The indirect method of assessing decentering introduced here may help to address some limitations inherent in a more explicit measure of decentering like the TMS. First, given that decentering is a higher-order meta-cognitive skill, it is possible that people’s perceived ability to separate themselves from their thoughts does not reflect their actual abilities or that some individuals may possess this ability but have limited self-awareness to report on it accurately. In contrast, the components of the indirect measure (frequency and negative reaction to repetitive thoughts) may be somewhat more accessible constructs for individuals to self-report. Second, an explict measure of decentering like the TMS is likely to include language that may overlap with meditation instructions. This is challenging to avoid given that both meditation instructions and the self-report measure are attempting to articulate the somewhat elusive construct of mindfulness in a manner that is meaningful to individuals with little or no prior exposure to the construct. Nonetheless, such overlap may artificially inflate the effects of mindfulness practice on self-reported decentering. In contrast, there is virtually no content overlap between the MB instructions used in the present study and the items assessing frequency and reaction to RT, which helps to rule-out content overlap as a confound.
As noted in the methods section, care was taken in selecting and developing a script for the present study that included minimal explicit discussion of decentering from thoughts to reduce potential demand characteristics. Nonetheless, it is important to address whether the results of the present study are tautological given that the MB instructions are intended to facilitate decentering through increasing awareness and acceptance of internal experience. We would argue the results were not a foregone conclusion given that different patterns of results would have been plausible. First, as noted previously, the effects of MB on decentering have not been examined in a study employing comparison groups that would be intended to be relaxing. Thus, it might have been possible that any activity that reduces arousal would produce comparable levels of decentering. Furthermore, although changes in self-reported decentering have been observed following full-length mindfulness-based interventions (Lau et al., 2006
), it is not clear if group differences would be detectable following brief practice in a sample of novice meditators.
In considering the generalizability of these results, it is important to note that the types of repetitive thought assessed in the present study are primarily negatively valenced (e.g., thoughts about life problems, self-criticisms). Such negatively-valenced repetive thoughts may be especially important to study given their relatively stronger link to negative emotional states (Watkins, 2008
). However, the present study is limited in terms of understanding how MB or other stress management exercises impact positively- or neutrally-valanced repetitive thoughts.
Another question that is unexplored in this study is whether the repetitive thoughts were perceived as helpful or unhelpful. Assessment of this dimension of repetitive thoughts would allow testing of whether MB helps to shift the style of repetitive thought such that it became more constructive. Past research has shown that repetitive thought that is concrete and solution-focused rather than abstract and evaluative tends to be associated with better outcomes (Watkins, 2008
). It is possible that the experiential, non-evaluative, non-elaborative nature of the MB instructions facilitated such a shift in the present study and this could help to explain why participants in the MB condition who experienced more frequent thoughts found them to be relatively less upsetting. This idea would be consistent with the model of Shapiro et al. (2006)
that suggests that reperceiving (a concept analogous to decentering) facilitates more intentional and effective choices in self-regulation, which could include use of concrete, specific thoughts when problem-solving. As noted previously, this model also posits that reperceiving facilitates exposure to upsetting internal sensations, rendering them less upsetting over time. Future research on mechanisms of mindfulness could help to clarify the direct and indirect effects of decentering, self-regulatory repetitive thought, and exposure in facilitating less negative reactions to thoughts and other mental health benefits of mindfulness practice. The present study is limited in its ability to tease apart such relationships given its focus on the immediate effects of mindfulness practice. Future studies using repeated assessment of these constructs especially with longitudinal follow-up assessments would be better suited to address this question.
Another area of concern is the self-report assessment of decentering and repetitive thoughts. Future studies would benefit from the use of more objective measures of these constructs through information-processing, “think aloud,” or psychophysiological assessment. In addition, it is worth noting that decentering and repetitive thought were not assessed prior to practice of the exercises (e.g., during period of silence without instruction). As such, it is possible that observed differences in decentering and repetitive thought post-practice were a function of baseline differences in groups not equalized through random-assignment. This possibility was unlikely, however, given that the three randomized experimental groups did not differ at baseline on any of the measured variables on which they were compared (meditation experience and NA), suggesting that the randomization procedure was successful in creating equivalent groups. Nonetheless, future experiments that include an examination of the relationship between frequency of RT and negative reactions to RT prior to a meditation practice would allow for examination of within-subject changes in decentering and repetitive thought as a function of mindful breathing.
A final limitation worth considering is the use of a sample of convenience. There are some advantages to studying mindfulness in non-clinical samples of novice meditators. Some have suggested that the potential mental and physical health benefits of mindfulness can be studied meaningfully in a range of populations given that mindfulness is a universal capacity (Brown, Ryan, & Creswell, 2007
). Similarly, mindfulness training is being increasingly applied as a form of stress-management for students in higher education settings (Shapiro et al., 2008
) and has been found to be effective in non-clinical samples (Chiesa & Serretti, 2009
). Nonetheless, it remains to be seen if the present results generalize to individuals with psychological disorders characterized by more severe and entrenched patterns of repetitive thoughts or experienced meditators with more practice observing thoughts from a decentered perspective. Furthermore, potential floor effects in the measure of negative affect in this non-clinical sample preclude meaningful examination of the effects of decentering on mood changes following practice of MB.
Despite these limitations, the present study helps to provide further evidence of decentering as potential mechanism that distinguishes mindfulness practice from other stress-management exercises. The present study adds to the clinical literature by examining the immediate effect of a specific mindfulness meditation practice on decentering. This is valuable given that mindfulness- and acceptance-based intervention approaches contain many components and experimental studies can isolate the effects of a specific practice or skill building exercise (Roemer & Orsillo, 2003
). The present study helps to establish that mindfulness of the breath may offer psychological benefits above and beyond other credible brief stress-management exercises.