Background

Meditation is used widely by both clinical populations and the general public to treat stress and stress-related conditions, as well as to promote health.^1,2 A number of hospitals and programs offer courses in meditation to patients seeking alternative or additional methods to relieve ailments or to promote health. Given the increasing use of meditation across a large number of conditions, examining the effects of meditation, type of meditation, conditions for which meditation is efficacious, and any mechanisms of action are important for patients, clinicians, and policymakers.

There remains uncertainty about the differences and similarities between the effects of different forms of meditation. Some have challenged “mindfulness” as a useful umbrella term for the practice, since it is understood and practiced in different ways.^3,4 Some “mindfulness” approaches such as Dialectical Behavioral Therapy (DBT) and Acceptance and Commitment Therapy (ACT) do not use mindfulness as the foundation but rather as an ancillary component. Others, such as yoga and tai chi, involve a significant amount of movement that could produce their own physiological effects apart from the mental exercises, potentially confounding any association between the mental activities of meditation and outcomes. Most of the other meditative programs involve a stilling of the mind in some form to increase awareness and then additional mental activity with that awareness that may have considerable overlap in practice. Academically, these programs have been described as “concentrative” meditation, such as Transcendental Meditation (TM), or “mindfulness” meditation such as MBSR (Mindfulness-Based Stress Reduction); however this distinction may not differentiate the effects of the techniques.³ The effectiveness of these interventions is unclear and may vary among different subgroups such as those with a particular clinical condition (e.g., anxiety or pain). This review will determine whether the effects of various meditation programs on various stress outcomes are similar or different.

The effects of the movement-based meditative techniques such as yoga, tai chi, and qi gong on stress outcomes are influenced by the ancillary beneficial effects of exercise/movement components on stress outcomes. Although these techniques also contain a meditative component, it is often difficult to ascertain the effects of meditation itself on stress outcomes, separate from the effects of the exercise component.^25,26 Many of the yoga interventions, in particular, do not clearly indicate how much meditation is involved in the intervention, leaving concerns that the inclusion of these studies will potentially confound conclusions about the effects of meditation. Like yoga, qi gong is a broad term encompassing both meditation and movement; it comes with some of the same difficulties as yoga in terms of parsing the effects of movement from the effects of meditation. Due to issues of scope, and to ensure consistency with the nomination, our review will largely focus on those meditative programs that are more purely meditative.

Meditation programs are varied and can be defined in a number of ways. To evaluate programs that are more than a brief mental exercise, yet remain broadly inclusive, we define a meditation program as any systematic or protocolized meditation program that follows a predetermined curriculum. We define these programs to involve, at a minimum, at least 4 hours of training with instructions to practice outside the training session.

While both clinical and healthy populations use meditation, this report seeks to assess the impact of the meditation programs on clinical populations. Although meditation is used by many as a way to promote health, the relevance of meditation programs for those with a disease or condition is more pressing for payers, clinicians, and patients. Since meditation is thought to have its effects by reducing the role of stress in the etiology of disease, we will include any population identified with a particular stressor as part of the spectrum of clinical conditions. The review will evaluate the effect of meditation programs on a range of important outcomes related to stress and well-being.⁵ The selected outcomes fall into domains based on the Patient Reported Outcomes Measurement Information System (PROMIS®) framework: negative affect, positive affect, well-being, cognition, and health-related behaviors affected by stress such as substance abuse, sleep, and eating behaviour.⁵ The review will also evaluate the effect of meditation programs on the clinical outcomes of pain and weight.

Previous Systematic Reviews on This Topic

A number of previous reviews have been conducted,^6-20 but they have been largely limited to one form of meditation or another (e.g., Mindfulness-Based Stress Reduction), usually with a narrow clinical focus on a limited range of outcomes.^6-21 These studies have demonstrated that meditation has an effect in largely uncontrolled or wait-list controlled studies. However, it is unclear whether these effects are specific to meditation and whether these effects are seen in higher quality trials with appropriate comparators.^22,23 A number of factors, such as attention and expectancy of benefit, can affect trial results from such studies. In a situation where double blinding may not be feasible, the burden of the design issues is higher to control for these types of effects.²⁵

Behavioral trials are susceptible to biases that may not be seen in pharmaceutical trials. However, prior reviews have tended to assess behavioral trials with the same bias measures used for pharmaceutical trials. They have underemphasized measures that are important for behavioral trials (e.g., controlling for expectancy) and have inadequately evaluated these expectancy effects as well as other risk-of-bias measures such as the blinding of outcome assessors.^25,26 While some reviews have focused on randomized controlled trials, many if not most of the included studies involved wait list or usual care controls. Additionally, previous reviews have overemphasized certain bias measures, such as blinding of the intervention in the Jadad scale, that are more appropriate for pharmaceutical interventions and not possible in meditative studies. Furthermore, given the anticipated large number of trials that have moved to a more rigorous design standard of using higher quality controls in recent years, a systematic review of such trials on the outcomes of stress with appropriate control for these design effects is potentially useful to decisionmakers and stakeholders. Hence, this systematic review will evaluate the effect of meditative programs on affect, attention, health-related behaviors affected by stress, pain, and weight, among those with a medical or psychiatric condition in randomized controlled trials.

Expected Use of the Report

A rigorous systematic review of meditation in addressing the effects on positive and negative affect, attention, well-being, health-related behaviors affected by stress, pain, and weight may be potentially useful to patients, clinicians, and policymakers. The results of the proposed review will likely be useful for clinicians and patients in making decisions about the best available options for stress reduction among these populations. The results of the proposed review will also inform developers of professional guidelines for these conditions. This review will also identify those areas in which evidence is adequate to inform the design of future studies in these areas.

The Key Questions

Summary of Revisions to Key Questions

As a result of public comment and input from the Technical Expert Panel (TEP), we have added a Key Question (KQ) on the clinical outcomes of pain and weight among those with a clinical condition.

To limit the scope of the review we will only evaluate meditative programs that are purely meditative, consistent with the original nomination. Thus, movement-based meditation programs will not be evaluated. Due to the need to limit scope, we have also focused on clinical populations.

We have replaced the KQ on physical function as it would primarily apply to the movement-based meditation programs and will not be addressed in this review. The movement-based programs require their own nomination and evaluation in a separate systematic review given the large number of randomized trials for these interventions.

We have refined KQ 2 to evaluate the effects on attention as this is a key outcome for understanding mechanisms. With respect to KQ 3, we have re-added evaluation of eating behavior on the recommendations of the TEP panel, since it appears to be heavily influenced by stress. Eating behavior will be measured by food diaries. However, since weight is affected by multiple inputs including eating, weight will be evaluated as its own clinical outcome in KQ 4 along with pain.

We also have removed the question about the time-course and pattern of changes because of the lack of clarity and specificity in the original question.

Analytic Framework

Figure 1: This figure depicts the Key Questions within the context of the PICOTS described in the previous section. Adverse events (AE) may occur at any point after the meditation program.

Methods

A. Criteria for Inclusion/Exclusion of Studies in the Review

B. Search Strategy

We will search the following databases for primary studies: MEDLINE®, PsycINFO®, EMBASE®, PsycARTICLES®, SCOPUS®, CINAHL®, and the Cochrane Library. We will develop a search strategy for MEDLINE, accessed via PubMed®, based on an analysis of the medical subject headings (MeSH®) terms and text words of key articles identified a priori. The search will be updated during the peer review process. The search strategy for MEDLINE can be found in Appendix A. We will also review the reference lists of each included article, relevant review articles and related systematic reviews. We will also use previous systematic reviews to identify studies. We plan to evaluate non–English-language studies and will update the search during the peer review process.

C. Data Abstraction and Data Management

We will use Distiller SR (Evidence Partners, Ottawa, Canada) to manage the screening and review process. Distiller SR is a Web-based database management program that manages all levels of the review process. All applicable citations identified by the search strategies are uploaded to the system.

Two independent reviewers will conduct title scans. For a title to be eliminated at this level, both reviewers will need to indicate that the study was ineligible. If the reviewers disagree, the article will be advanced to the next level, abstract review.

Abstracts will be reviewed independently by two investigators and will be excluded if both investigators agree that the article meets one or more of the exclusion criteria (see inclusion and exclusion criteria listed in Table 2). Differences between investigators regarding abstract inclusion or exclusion will be tracked and resolved through consensus adjudication. Articles promoted on the basis of abstract review will undergo another independent parallel review to determine if they should be included in the final qualitative and quantitative systematic review and meta-analysis. The differences regarding article inclusion will be tracked and resolved through consensus adjudication. We will maintain a list of excluded articles and the potential reasons for exclusion.

We will use a systematic approach for extracting data to minimize the risk of bias in this process. We will create standardized forms for data extraction, which will be pilot tested. By creating standardized forms for data extraction, we will maximize consistency in identifying all pertinent data available for synthesis. Each article will undergo double review by study investigators for data abstraction. The second reviewer will confirm the first reviewer’s data abstraction for completeness and accuracy. Reviewer pairs will be formed to include personnel with both clinical and methodological expertise. A third reviewer will audit a random sample of articles reviewed by the first two reviewers to ensure consistency in the data abstraction of the articles. Reviewers will not be masked to the articles’ authors, institution, or journal. For all articles, reviewers will extract information on general study characteristics (e.g., study design, study period, and followup), study participants (e.g., age, gender, race, comorbidities), eligibility criteria, interventions, outcome measures and the method of ascertainment, and the results of each outcome, including measures of variability.

For each meditation program, we will extract information on measures of intervention fidelity including dose, training, and receipt of intervention by measuring 1) duration of structured training in meditation for the participants; 2) mean hours of total meditation (training + home); 3) hours/duration of recommended practice; 4) description of participant compliance, if any; 5) description of participant proficiency in practicing the meditation technique; and 6) description of instructor qualifications.

All information from the article review process will be entered into the Distiller SR database by the individual completing the review. Reviewers will enter comments into the system whenever applicable. The Distiller SR database will be used to maintain the data, as well as to create detailed evidence tables and summary tables.

D. Assessment of Risk of Bias of Individual Studies

The risk of bias of included trials will be conducted independently and in duplicate based on the recommendations in the Methods Guide for Effectiveness and Comparative Effectiveness Reviews (hereafter Methods Guide).²⁹ We will supplement these tools with additional assessment questions based on the Cochrane Collaboration’s Risk of Bias Tool.^30,31 The selected risk-of-bias items are outlined below. For example, while double blinding may not be possible in meditation studies, we will evaluate blinding of data collection personnel, especially with subjective outcomes. In addition, we will assess whether the attention control was matched on expectation, time, and attention. One reviewer will extract information, and a second senior reviewer will verify the information. A third reviewer will resolve discrepancies.

Selection Bias:

• Was the method of randomization described in the paper, and was it appropriate (random number generator or table; allocation concealment)?
• Did the strategy for recruiting participants into the study differ across study groups?

Performance Bias:

• Was the control matched for time and attention by the instructors (100%, 75%, ≤50%)?
• Was an assessment for credibility of the control used?
• Was it adequate? (For example, would you recommend this to your friends?)

Attrition Bias:

• Was there a description of withdrawals and dropouts? If so, was there a high rate of attrition of differential or overall attrition?
• Did attrition result in a difference in group characteristics between baseline and followup?
• Was intent-to-treat analysis used?

Detection Bias:

• Were those who collected data on the participants blind to the allocation?
• Are the inclusion/exclusion criteria measured using valid and reliable measures and implemented consistently across all study participants?
• Are interventions/exposures assessed using valid and reliable measures and implemented consistently across all study participants?
• Are primary outcomes assessed using valid and reliable measures and implemented consistently across all study participants?

Reporting Bias:

• Are the potential outcomes prespecified by researchers?
• Are all prespecified outcomes reported?

The overall risk of bias will be assessed as:

• Good (low risk of bias). These studies had the least bias, and the results were considered valid. These studies adhered to a clear description of the population, setting, approaches, and comparison groups; appropriate measurement of outcomes; appropriate statistical and analytic methods and reporting; no reporting errors; a low dropout rate; and clear reporting of dropouts.

• Fair. These studies were susceptible to some bias, but not enough to invalidate the results. They did not meet all the criteria required for a rating of fair because they had some deficiencies, but no flaw was likely to cause major bias. The study may have been missing information, making it difficult to assess limitations and potential problems.

• Poor (high risk of bias). These studies had significant flaws that might have invalidated the results. They had serious errors in design, analysis, or reporting; large amounts of missing information; or discrepancies in reporting.

E. Data Synthesis

For each KQ, we will create a set of detailed evidence tables containing all information abstracted from eligible studies. We will conduct meta-analyses when there are sufficient data (at least three studies that are sufficiently homogenous with respect to the population characteristics and study duration and meditation "dose"). We will conduct narrative synthesis when study results cannot be combined.

For studies amenable to pooling with meta-analyses, we will calculate pooled mean differences, risk differences, or relative risks using a DerSimonian and Laird random-effects model. For studies with continuous outcomes we will only combine studies using mean differences if multiple trial reports use the same or similar scales. We will use the standardized mean difference (SMD) when the same outcome (such as anxiety or depression) is measured with different scales. SMD is the mean difference divided by a measure of within group standard deviation. Effect sizes will be estimated in standard deviation units, using either Cohen’s d or Hegde’s g for all studies that provide sufficient data.³²

We will identify statistical heterogeneity between the trials in all the meta-analyses using: 1) a chi-squared test with a significance level of alpha less than or equal to 0.10, and 2) an I-squared statistic with a value greater than 50 percent indicating substantial heterogeneity. We will not report the pooled result if substantial heterogeneity is found. We will conduct sensitivity analyses by omitting one study at a time to assess the influence of any single study on the pooled estimate. For all meta-analyses, we will conduct formal tests for publication bias using Begg’s and Egger’s tests, including evaluation of the asymmetry of funnel plots for each comparison of interest. All meta-analyses will be conducted using STATA (Intercooled, version 11, StataCorp, College Station, TX) or Stats Direct (StatsDirect Ltd., Cheshire, United Kingdom).

When we are unable to pool studies, we will calculate and display the individual mean differences, risk differences, or relative risks with 95 percent confidence intervals for the individual studies. We will model rare adverse events (<1%) using the Peto odds ratio approach, which has the best confidence interval coverage for rare events, because the random-effects model is statistically underpowered.³³ If we detect an imbalance in trial sizes and number of zero event studies, appropriate sensitivity analysis using treatment arm continuity correction approaches will be conducted.³⁴

F. Grading the Evidence for Each Key Question

At the completion of our review, we will grade the quantity, quality, and consistency of the best available evidence addressing KQs 1–6 by adapting an evidence grading scheme recommended in the Methods Guide.²⁹ In assigning evidence grades we will consider the domains of risk of bias of included studies, directness, consistency, precision, and publication bias. We will also consider additional domains such as biological plausibility, dose-response effect, and impact of plausible confounders when applicable. Evidence will be graded for the outcomes in the KQs.

We will classify evidence pertaining to the KQs into four basic categories: 1) “high” grade (indicating high confidence that the evidence reflects the true effect and further research is very unlikely to change our confidence in the estimate of the effect); 2) “moderate” grade (indicating moderate confidence that the evidence reflects the true effect and further research may change our confidence in the estimate of the effect and may change the estimate); 3) “low” grade (indicating low confidence that the evidence reflects the true effect and further research is likely to change our confidence in the estimate of the effect and is likely to change the estimate); and 4) “insufficient” grade (evidence is unavailable).

G. Assessing Applicability

Applicability will be assessed separately for the different outcomes for the entire body of evidence, guided by the PICOTS framework as recommended in the Methods Guide.²⁹ Potential factors to be assessed that may limit applicability include intervention fidelity (such as duration of structured meditation training), total amount of meditation practice (dose of meditation), subject compliance with meditation, subject proficiency with meditation, instructor qualifications, and study selection criteria for participants. There are concerns that participants in meditation studies are highly selected, such as trained meditators. We will evaluate the selection process of these studies to determine such issues around applicability. We will also examine whether race or ethnicity or education modifies the effect of meditation.

References

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Definition of Terms

MBSR = Mindfulness-Based Stress Reduction
MBCT= Mindfulness-Based Cognitive Therapy
TM = Transcendental Meditation
ACT = Acceptance and Commitment Therapy
DBT = Dialectical Behavioral Therapy

Summary of Protocol Amendments

Protocol Amendments on October 10, 2012

Review of Key Questions

For all EPC reviews, key questions were reviewed and refined as needed by the EPC with input from Key Informants and the Technical Expert Panel to assure that the questions are specific and explicit about what information is being reviewed. In addition, the key questions were posted for public comment and finalized by the EPC after review of the comments.

Key Informants

Key Informants are the end-users of research, including patients and caregivers, practicing clinicians, relevant professional and consumer organizations, purchasers of health care, and others with experience in making health care decisions. Within the EPC program, the Key Informant role is to provide input into identifying the Key Questions for research that will inform health care decisions. The EPC solicits input from Key Informants when developing questions for systematic review or when identifying high-priority research gaps and needed new research. Key Informants are not involved in analyzing the evidence or writing the report and have not reviewed the report, except as given the opportunity to do so through the peer or public review mechanism.

Key Informants must disclose any financial conflicts of interest greater than $10,000 and any other relevant business or professional conflicts of interest. Because of their role as end-users, individuals are invited to serve as Key Informants and those who present with potential conflicts may be retained. The TOO and the EPC work to balance, manage, or mitigate any potential conflicts of interest identified.

Technical Experts

Technical Experts comprise a multidisciplinary group of clinical, content, and methodological experts who provide input in defining populations, approaches, comparisons, or outcomes as well as identifying particular studies or databases to search. They are selected to provide broad expertise and perspectives specific to the topic under development. Divergent and conflicted opinions are common and perceived as healthy scientific discourse that results in a thoughtful, relevant systematic review. Therefore study questions, design and/or methodological approaches do not necessarily represent the views of individual technical and content experts. Technical Experts provide information to the EPC to identify literature search strategies and recommend approaches to specific issues as requested by the EPC. Technical Experts do not do analysis of any kind nor contribute to the writing of the report and have not reviewed the report, except as given the opportunity to do so through the public review mechanism.

Technical Experts must disclose any financial conflicts of interest greater than $10,000 and any other relevant business or professional conflicts of interest. Because of their unique clinical or content expertise, individuals are invited to serve as Technical Experts and those who present with potential conflicts may be retained. The TOO and the EPC work to balance, manage, or mitigate any potential conflicts of interest identified.

Peer Reviewers

Peer reviewers are invited to provide written comments on the draft report based on their clinical, content, or methodological expertise. Peer review comments on the preliminary draft of the report are considered by the EPC in preparation of the final draft of the report. Peer reviewers do not participate in writing or editing of the final report or other products. The synthesis of the scientific literature presented in the final report does not necessarily represent the views of individual reviewers. The dispositions of the peer review comments are documented and will, for CERs and Technical briefs, be published 3 months after the publication of the Evidence report.

Potential Reviewers must disclose any financial conflicts of interest greater than $10,000 and any other relevant business or professional conflicts of interest. Invited Peer Reviewers may not have any financial conflict of interest greater than $10,000. Peer reviewers who disclose potential business or professional conflicts of interest may submit comments on draft reports through the public comment mechanism.

Appendix A

MEDLINE search strategy via PubMed:

meditation[mh] OR meditat*[tiab] OR mindful*[tiab] OR transcendental Meditation[mh] OR "transcendental Meditation"[tiab] OR "mindfulness-based cognitive therapy"[tiab] OR "MBCT"[tiab] OR "mindfulness-based stress reduction"[tiab] OR "MBSR"[tiab] OR Vipassana[tiab] OR zen[tiab] OR Qi-gong[tiab] OR Qigong[tiab] OR Chi kung[tiab] OR Tai Chi[tiab] OR TaiChi[tiab] OR tai ji[mh] OR Yoga[mh]OR yoga[tiab] OR Yogic[tiab]OR dhyana[tiab] OR asana[tiab] OR pranayama[tiab] OR sudarshan[tiab]