Background
Low back pain is a major public health problem, with 76 % of the population experiencing low back pain in a given year[
1]. It has become the largest category of medical claims, placing a major burden on individuals and health care systems[
2]. Low back pain is the most common condition for which complementary therapies are used[
3]. In the US, more than half of patients suffering from low back pain use complementary therapies[
4].
Mindfulness is the common ground of several complementary therapies. Derived from Buddhist spiritual tradition, mindfulness has been secularized and integrated into behavioral treatment approaches[
5]. While mindfulness has been described as the core construct of Buddhist meditation[
5], it also comprises a specific state of consciousness that has been characterized as non-elaborative, non-judgmental moment-to moment awareness, a way to accept and trust in one’s own experience[
6]. Therefore, mindfulness-based therapies not only include training in so-called formal practice of mindfulness, this is meditation, but also training in so-called informal practice of mindfulness, this is retaining a mindful state of consciousness during routine activities in everyday life[
7,
8].
The most commonly used mindfulness-based intervention is mindfulness-based stress reduction (MBSR). MBSR has originally been developed in a behavioral medicine setting for patients with chronic pain and stress-related complaints[
9,
10]. MBSR is a structured 8-week group program of weekly 2.5-hour sessions and 1 all-day (7 to 8-hour) silent retreat. Key components of the program are sitting meditation, walking meditation, hatha yoga and body scan, a sustained mindfulness practice in which attention is sequentially focused on different parts of the body[
6]. Another important component is the transition of mindfulness into everyday life.
Mindfulness-based cognitive therapy (MBCT) combines MBSR with cognitive-behavioral techniques[
11,
12]. It retains the original 8-week group-based approach. Originally developed as a treatment for major depression[
11], MBCT is more and more adapted for other specific conditions[
12]. Other mindfulness-based interventions include mindful exercise[
13] and acceptance and commitment therapy[
14] that do not necessarily include formal meditation practice.
Pain has been a key topic of research on MBSR from the beginning[
9]. Several trials assessed the effect of MBSR on patients with heterogeneous chronic pain conditions, mainly reporting positive results[
15‐
19]. A recent comprehensive meta-analysis of mindfulness-based interventions for chronic pain conditions found small effects on pain, depression and physical well-being when considering only randomized controlled trials[
14]. However, this meta-analysis included only one trial on low back pain.
The aim of this review was to systematically assess and - if possible - meta-analyze the effectiveness of MBSR and MBCT in patients with low back pain.
Methods
PRISMA guidelines for systematic reviews and meta-analyses[
20] and the recommendations of the Cochrane Collaboration[
21] were followed.
Literature search
The literature search comprised the following electronical databases from their inception through November 2011: Medline, EMBASE, the Cochrane Library, PsycINFO, and CAMBASE. The complete search strategy for Medline was as follows: (MBSR[Title/Abstract] OR MBCT[Title/Abstract] OR mindful*[Title/Abstract]) AND (low back pain[MeSH Terms] OR low back pain[Title/Abstract] OR lower back pain[Title/Abstract] OR lumbago[Title/Abstract] OR low backache[Title/Abstract] OR low back ache[Title/Abstract] OR sciatica[MeSH Terms] OR sciatica[Title/Abstract]). The search strategy was adapted for each database as necessary. No language restrictions were applied. In addition, reference lists of identified original articles were searched manually. All retrieved articles were read in full to determine eligibility.
Eligibility criteria
Intervention
Studies that assessed MBSR or MBCT as the main intervention were included. Studies on mindfulness-based interventions that were clearly different from the original MBSR/MBCT programs, such as mindful exercise or acceptance and commitment therapy, were excluded while studies that used variations of the MBSR/MBCT programs, such as variations in program length, frequency or duration were included.
Study type
Only randomized controlled trials (RCTs) were included, while observational studies or non-randomized trials were excluded. No treatment (“wait-list”), usual care or any active treatment were acceptable as control interventions.
Studies were included only if they were published as full-text articles in peer reviewed scientific journals.
Patients
Studies of patients with a diagnosis of low back pain were included regardless of pain cause, duration and intensity.
Two reviewers independently extracted data on characteristics of the study (e.g. trial design, randomization, blinding), characteristics of the patient population (e.g. sample size, age, diagnosis), characteristics of the intervention and control condition (e.g. type, program length, frequency and duration), drop-outs, outcome measures, follow-ups, results and safety. Discrepancies were rechecked with a third reviewer and consensus achieved by discussion.
Risk of bias in individual studies
Risk of bias was assessed by two authors independently using the Cochrane risk of bias tool. This tool assesses risk of bias on the following domains: selection bias, performance bias, detection bias, attrition bias, reporting bias, and other bias[
21]. Discrepancies were rechecked with a third reviewer and consensus achieved by discussion. Trial authors were contacted for further details if necessary.
Data analysis
Main outcome measures were pain intensity and back-related disability. Safety was defined as secondary outcome measure. Other outcome measures used in the included studies were analyzed exploratively.
Meta-analysis was planned if sufficient homogeneous RCTs were available for statistical pooling. However, as only 3 RCTs were available that were heterogeneous regarding characteristics of patients, interventions, and control conditions, no meta-analysis was performed.
To determine clinical importance of group differences the following criteria were used: 10 mm (or 10 %) difference in post-treatment scores or change scores on a 100 mm visual analog scale of pain intensity[
22], and 2–3 points (or 8 %) difference in post-treatment or change scores on the Roland-Morris Disability Questionnaire for back-specific disability[
23].
Discussion
This systematic review found only limited evidence that MBSR can provide short-term relief of pain and back-related disability in low back pain patients. Statistical significant and clinically relevant group differences were reported in only 1 out of 3 RCTs. Single studies reported effects on physical or emotional well-being but overall, only little effects on quality of life were reported. These results are only partly in line with a recent meta-analysis on mindfulness-based interventions for chronic pain that found MBSR to be superior to controls in reducing pain intensity and increasing physical wellbeing but not in increasing quality of life[
14]. However, this meta-analysis included only 1 of the RCTs included in the present review[
25].
Methodological differences between the included RCTs might explain some of the differences in results: firstly, different control groups were chosen; while 1 RCT used an adequate active control group[
26], 2 RCTs compared MBSR to no treatment[
24,
25] and 1 of those was the only study that reported positive intervention effects on most of the study outcomes[
24]. Secondly, another source of heterogeneity are differences in inclusion criteria between studies: the study that showed favorable effects of MBSR included a sample of highly chronified specific low back pain patients[
24] while the 2 trials that showed little effects included patients with specific or unspecific low back pain[
25,
26]. Moreover, the 2 RCTs that did not report significant group differences in pain intensity or back-related disability included only older adults[
25,
26] while no age restriction was posed in the only RCT that reported effectiveness of MBSR for most outcome measures[
24]. It has been argued that standard pain measurement instruments might not be suitable for elderly patients[
27,
28]. Specialized comprehensive approaches might be needed to correctly assess pain intensity in elderly patients[
28]. Thirdly, the 2 RCTs that did not report significant group differences did not include yoga or an all-day retreat in their MBSR program[
25,
26]. Yoga has been reported to increase back-related function and to decrease disability in patients suffering from low back pain[
29,
30]. As the only RCT that reported favorable effects of MBSR on functional disability actually included yoga in the MBSR program[
24], yoga might be crucial for this effect. Further research should include dismantling studies that separately evaluate the effects of different components of MBSR such as mindful meditation and yoga.
Although the use of pain intensity and disability as main outcome measures is in accordance with the IMMPACT recommendations[
31], pain relief is not the main aim of MBSR[
14]. Instead, patients are guided to accept all varieties of experience, be them pleasant or unpleasant, without elaboration or judgment[
5,
6]. In accordance with this approach, 2 RCTs reported increased pain acceptance after MBSR interventions[
24,
25]. Pain acceptance describes patients’ attempt to maintain function in spite of their pain as far as possible[
32]. Higher pain acceptance has been found to be associated with lower pain intensity and disability[
33]. However, whether or not pain acceptance is a mechanism by which MBSR relieves pain in low back pain patients is beyond the scope of this review.
At the moment there is no evidence for longer-term effects of MBSR in low back pain. More RCTs with longer follow-ups are needed.
Generally, adverse events and reasons for drop-outs were poorly reported. This is unsatisfying since safety is a major issue in evaluating therapies. Further trials should put a focus on detailed reporting of safety data.
All included RCTs used MBSR as an intervention. No RCT assessing the effectiveness of MBCT in low back pain patients could be located. This is in line with the aforementioned meta-analysis of chronic pain that could not locate any trials on MBCT either[
14].
The evidence found in this review is clearly limited due to several reasons. Firstly, the total number of eligible RCTs was small and clinical heterogeneity was high between RCTs. Thus, no meta-analysis could be performed. This review only included trials that were published in peer reviewed scientific journals. Therefore, some RCTs that were published in “grey literature” or conference proceedings only might have been missed. Secondly, the total number of included patients was low. No study included more than 20 patients in each group. More large RCTs are needed to definitely judge the effects of MBSR in low back pain. Thirdly, the evidence was suspect to high attrition bias. Fourthly, 2 out of 3 RCTs compared MBSR with wait-lists. While there is limited evidence that MBSR is effective in low back pain, more research is needed to evaluate superiority or inferiority of MBSR to other active treatments.
Competing interests
All authors disclose any commercial association that might create a conflict of interest in connection with the submitted manuscript. There is especially no competing financial interest for any of the authors.
Authors’ contributions
HC was responsible for conception and design of the review, carried out the literature search, performed data analysis, and drafted the manuscript. HH and RL performed data extraction and assessment of risk of bias, participated in conception and design of the review, and critically revised the manuscript. GD participated in conception and design of the review, and critically revised the manuscript. All authors read and approved the final manuscript.