Mindfulness-based interventions (MBIs) emphasizing nonjudgmental attitudes toward present-moment experiences have been widely used to help patients with chronic pain. Although changing or controlling pain is not always an explicit aim of MBIs, a recently reported review of research studies suggests that mindfulness practices may lead to favorable changes in pain tolerance and intensity ratings. However, the evidence in this regard seems neither robust nor highly convincing.
According to background information in the research review article by Keren Reiner, MA, MSc and associates — from the Department of Psychology, Ben Gurion University of the Negev, Beer Sheva, Israel — mindfulness emphasizes a form of detachment whereby thoughts, perceptions, and emotions occupying awareness at the present moment are self-observed without judgment and without attempts to change or control them [Reiner et al. 2013]. Much of the past research has assessed effects on global distress, physical functionality, and quality of life; whereas, benefits of MBI for modulating pain itself have been less studied.
The best investigated among the many approaches to MBI are Mindfulness-Based Stress Reduction (MBSR) and Acceptance and Commitment Therapy (ACT), which Reiner et al. describe as follows:
- MBSR is guided by the rationale that the practice of mindfulness leads to a spontaneous uncoupling of the sensory component of pain from the cognitive and emotional components and, by doing so, reduces the amount of suffering caused by pain. In MBSR, individuals practice yoga and different meditations, such as breathing meditation or body scan meditation.
- ACT combines mindfulness practice with work on personal values, behavioral commitment, and traditional behavior change strategies to help patients live a fuller life. Core principles of ACT are introduced to participants using metaphors, paradoxes, and experiential exercises; whereas, formal meditation is considered only one of multiple ways to acquire mindfulness skills.
Mindfulness techniques, which come under the umbrella of Complementary and Alternative Medicine (CAM), most typically target the psychological correlates of pain with the explicit goal of improving functioning and lowering distress in general, rather than solely reducing the intensity of pain. However, there have been some studies focusing on pain reduction facilitated by MBIs; so, Reiner and colleagues devised a systematic literature review to further investigate the issue.
Their search spanned 1960 through 2010, and studies were included if they used standardized MBI techniques — most commonly MBSR or ACT — and assessed effects on traditional pain-intensity rating scales from pre- to posttreatment. Additionally, mindfulness studies had to encompass at least 6 hourly training sessions, include a minimum of 10 participants in the treatment group, and enroll participants ≥18 years of age. Only studies of clinically-relevant pain were considered, which excluded experimental trials using laboratory-induced pain.
Writing in the March 2013 edition of Pain Medicine, the researchers report that 16 of 133 candidate studies uncovered in the search qualified for inclusion. Here are some details:
- Half (8) of the studies were uncontrolled, observational trials and the remaining 8 were controlled trials, involving as a control condition; either a wait list, treatment as usual, or a comparator treatment (eg, cognitive behavioral therapy, or CBT).
- Sample sizes in the selected studies ranged from 14 to 228 participants, with a total of 1,404 overall. The mean age of participants was ≈48 years (range 30-85 years). Most studies had a majority of women (62%–100%); only 3 studies had roughly equal numbers of men and women.
- Eleven of the 16 studies (≈69%) included patients with chronic pain; 6 of those comprised patients with diverse pain diagnoses and 5 involved specific conditions — eg, fibromyalgia (3 studies); rheumatoid arthritis (1); back pain (1). The remaining 5 studies did not limit their samples to participants with diagnosed pain conditions.
- Based on pre-established assessment criteria, only 1 study was rated as high quality and 2 studies were rated as medium quality. The remaining 13 studies were all rated as being of low quality based on such deficiencies as small sample size (lack of statistical power), incomplete data, inadequate randomization, and other faults.
Results from the 8 uncontrolled, observational studies found statistically significant reductions in pain-intensity ratings following MBI in 3 trials among patients with chronic pain. In contrast, mixed and normal (healthy) samples failed to show benefits favoring MBI with respect to pain intensity. Followup investigations demonstrated that the immediate reductions in pain intensity among chronic pain patients were generally sustained during 3 months.
Of the 8 controlled trials, 6 found that reductions in pain intensity were statistically significant in the MBI group compared with controls. In 1 study, MBI produced similar pain reduction compared with a CBT control condition. A second study failed to find a significant difference between MBI and a treatment as usual control group. Results from followup assessments in the 3 positive trials that measured the effect found that initial pain-intensity reductions after MBI persisted over time.
In conclusion, Reiner et al. observe that most of the studies (9/16) demonstrated a statistically significant decrease in pain intensity among persons receiving MBIs. The findings were more consistently positive for samples limited to persons with clinical pain. Additionally, most controlled trials (6/8) revealed higher reductions in pain intensity for MBIs compared with control groups, and results from followup assessments revealed that reductions in pain intensity were generally well maintained. Consequently, along with other beneficial effects of mindfulness approaches, MBIs also may help to reduce pain intensity.
COMMENTARY: It is well-established that chronic pain is a multidimensional experience comprised of sensory, affective, and cognitive components. Mindfulness-based interventions may exert an influence on all 3 dimensions; although, the prior probability or scientific plausibility of MBI — eg, neurobiological mechanisms and rationales — still need refinement, as with many other psychological approaches.
The present review by Reiner and colleagues focused on changes in pain intensity resulting from MBI and, admittedly, this may not be the only or even the most important clinical outcome for MBI or for other pain-focused interventions. Yet, there is great concern these days in the pain management community about finding alternatives to pharmacotherapy, particularly opioid analgesics, for providing pain relief. Unfortunately, despite the researchers’ claims, the evidence for MBI in this particular review is neither very strong nor compelling.
From an evidence-based perspective, there were many limitations of this review, some of which the researchers noted themselves: [Caveat: some readers may find these details tedious and want to skip past them.]
- The minimum threshold of 10 participants per group set by the researchers for study inclusion was probably too low. Other researchers have noted that small trials with fewer than 50 participants per treatment arm are potentially biased by the random play of chance and other methodological problems that overestimate treatment effects [Moore et al. 2010]. Half (4/8) of the uncontrolled, observational studies in this review by Reiner et al. — all rated as low quality — had only from 14 to 28 subjects and probably should have been omitted from consideration. Outcome results in these trials were mixed and not statistically significant.
- Similarly, half (4/8) of the controlled trials had only from 10 to 39 subjects in the various groups; 3 of the studies were rated as low quality and the smallest trial (15 in treatment group, 10 controls) was curiously 1 of only 2 studies rated as being of medium quality. Three of the 4 trials produced statistically significant effects favoring MBT, but the validity of these results could be challenged.
- A large majority of studies (13/16) included data only for treatment completers in their final outcome analyses, which could bias results to favor MBI. Two of 3 studies that reported results for an intent-to-treat (ITT) sample (ie, for all patients who began treatment with last observation carried forward) found that pain-intensity reductions were not significant. The 3rd study using an ITT analysis found MBI was comparable with cognitive behavioral therapy.
- Most (6/8) of the controlled trials lacked randomization. In nonrandomized trials, allocation was generally based on participants’ location or time of attending the study and this may have influenced between-group variance that biased results. In one study, patients self-selected the group they preferred, which can skew outcomes in many ways.
- Among 5 of 6 controlled trials that found statistically significant improvements associated with MBI, effect sizes were moderate. The 1 trial with a large effect size (Cohen’s d=1.02) also had the fewest number of completers (15 MBI, 10 controls), and was most likely skewed. Effect sizes in the 3 observational trials finding significant outcomes ranged from d=0.49-0.65 (all moderate), the absolute mean pain-score changes were relatively small (13% to 17%), and 2 of the trials were of low quality.
- Finally, Reiner and colleagues note that only a single study discussed clinical significance of improvements associated with MBI, in terms of the number of participants achieving substantial decreases of pain ratings. MBI was noted to be favorable, but this was an observational trial, from 1993, which also had a high (23%) attrition rate and was rated as being of low quality.
In sum, the aggregate evidence supporting mindfulness approaches for helping to relieve pain in persons with chronic pain appears to be unimpressive. As we have noted previously in these UPDATES, a collection of low-quality and potentially biased studies does not amount to convincing evidence in support of a therapy or practice. Reiner and colleagues, themselves — all of whom are presumably psychologists — concede that there is a “clear shortage of high-quality studies” to support MBI and recommend that further research is needed.
It is interesting that, while the researchers note previous meta-analyses had been conducted on studies of MBIs, they made no attempt at a consolidated quantitative analysis regarding their findings for pain intensity. Probably, the overall low quality of the evidence and inadequate data reporting, combined with a high degree of heterogeneity (differences in methodology) across studies, convinced them that this would be futile.
Furthermore, Reiner at al. acknowledged that, in the case of the observational trials, these “do not provide evidence of a specific association between mindfulness practice and pain reduction.” It is possible that many other factors, including nonspecific effects of MBI on expectation of improvement, may have influenced outcomes in the few uncontrolled studies finding significantly positive results.
Finally, if considering a recommendation of MBI for patients with chronic pain, there is the unresolved question of who might benefit. For example, patients of any age with cognitive impairments, or even mental clouding associated with their pain conditions or medications, might not respond to such interventions. Or, some patients may find chronic pain that is uncontrolled by other means so distracting that participation in MBT becomes difficult and unsuccessful.
> Moore RA, Eccleston C, Derry S, et al. “Evidence” in chronic pain — establishing best practice in the reporting of systematic reviews. PAIN. 2010;150:386-389 [access by subscription].
> Reiner K, Tibi L, Lipsitz JD. Do Mindfulness-Based Interventions Reduce Pain Intensity? A Critical Review of the Literature. Pain Med. 2013;14:230–242 [abstract here].
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