Headache is one of the most common disorders of the nervous system and several subtypes such as tension-type headache (TTH) and migraine remain underrecognized and undertreated. Since 1990, headache has ranked among the top three diseases among the several hundred contributors to the global burden of disease. In the Asia-Pacific region, the median 1-year prevalence of primary headache such as migraine and TTH were 9.1% and 16.2%, respectively. In Europe, the prevalence of TTH and migraine were 60% and 15%, respectively. Prolonged use of medication (such as caffeine, aminopyrine, phenacetin, and phenobarbital) may lead to medication-overuse headache and other side effects. Besides biofeedback treatment, biopsychosocial interventions such as mindfulness meditation have been used to treat headache due to their high cost-effectiveness and fewer side effects.
Meditation is defined as a form of mental training that aims to improve an individual's core psychological capacities, such as attentional and emotional self-regulation. There are three core components of meditation practice as follows: attention control, emotion regulation, and self-awareness. Meditative techniques include transcendental meditation, mindfulness-based stress reduction (MBSR), and mindfulness-based cognitive therapy (MBCT). Transcendental meditation emphasizes the use of a mantra by which one is transcended to an effortless state in which focused attention is absent. MBSR focuses on the training in awareness or mindfulness that focuses on the present. MBCT has been used to prevent relapse of major depression. Although several studies have investigated the use of meditative techniques for treatment of headache, the intensity, frequency, and duration of headache in the respective study populations have tended to vary.
Therefore, the purpose of this meta-analysis was to assess evidence regarding the effectiveness of meditation programs in dealing with primary headache and associated clinical outcomes and to determine whether meditation programs are a viable complementary and alternative medical therapeutic option for primary headaches.
Database and literature search strategy
We searched the literature in the following databases: PubMed, Cochrane Central Register of Controlled Trials (the Cochrane Library), PsycINFO, Psychology and behavioral science collection, PsyArticles, Web of Science, and Scopus from inception to November 2016. Key words used for the search were “meditation” or “mindfulness” or “vipassana” or “dzogchen” or “zen” or “integrative body-mind training” or “IBMT” or “mindfulness-based stress reduction” or “MBSR” or “mindfulness-based cognitive therapy” or “MBCT” in combination with “Headache” or “Head pain” or “Cephalodynia” or “Cephalalgia” or “Hemicrania” or “Migraine.” These searches were limited to English publications. All potentially relevant studies, articles (including undocumented data and meta-analyses), and international guidelines were searched manually. The eligibility of identified citations was independently reviewed by two reviewers. An example of search strategy was shown as Supplementary File 1.
Example of search strategy
Selection procedure and eligibility criteria
Inclusion criteria were as follows: (1) age 18 or older with primary headache (mainly, migraine or TTH) according to the diagnostic criteria of the International Headache Classification Subcommittee; (2) randomized controlled trials or controlled clinical trials for whom full text were available; (3) intervention of interest: structured meditation programs (any systematic or protocol meditation programs that follow predetermined curricula) including mindfulness-based programs (i.e., MBSR, MBCT, vipassana, Zen, and other mindfulness meditation), mantra-based programs (i.e., transcendental meditation, other mantra meditation), and other meditation programs; (4) comparison: relaxation, education, usual pharmacotherapy, delayed treatment, or wait-list. Exclusion criteria were as follows: additional diseases that might interfere with the primary headache such as human immunodeficiency virus-related pain, cancer pain, seizures, facial neuralgia, significant cognitive impairment, schizophrenia, bipolar affective disorder, and current substance abuse. No limitations of race, religion, or gender of the study population were imposed. Studies were independently screened by two investigators. All analyses were based on previously published studies, thus no ethical approval and patient consent were required. This study conforms to all preferred reporting items for systematic reviews and meta-analyses guidelines and reports the required information accordingly.
Data extraction and quality assessment
The following data were obtained: study characteristics (e.g., author, year, and country); patient characteristics (e.g., age and sample size); description of interventions and duration, and outcomes measured. Primary outcomes were headache intensity, frequency, and duration. Headache intensity reflected self-assessed headache severity according to numeric rating scales. Headache frequency and duration were defined as the days of headache attacks per unit of time and the duration of the attack, respectively. Quality of life, self-efficacy, pain tolerance, and perceived stress were secondary outcomes. Two reviewers independently extracted these data using predefined criteria. Primary authors of the selected publications were contacted when the relevant information was not reported. The Yates Quality Rating Scale (YQRS) was used to assess the quality of psychological trials for chronic pain. The Yates Scale of 35 scores is composed of 26 items including specific psychological interventions such as the assessment of therapist training and treatment expectation. This scale is deemed to have good construct validity and reliability. A percentage was calculated from the final score so that trials could be compared. A Cochrane review used the midpoint (score of 18) as the divider between a “high-quality” and “low-quality” study. Therefore, in this meta-analysis, a score ≥50% was deemed to have low risk of bias and a score ≤49% was deemed to have high risk of bias. Studies of low quality were also displayed in the results. Data from each included article were extracted independently by two investigators. In cases where a consensus could not be reached, the opinion of a third independent investigator was sought.
All variables were analyzed using the standardized mean difference (SMD) and 95% confidence interval (CI). SMD was calculated with Hedge's g formula. Heterogeneity was assessed by Cochrane's Q statistic (P < 0.10 was considered to be statistically significant) and was quantified by the I2 index (I2 >30%, >50%, and >75% indicate moderate, substantial, and considerable heterogeneity, respectively). Then, we undertook a conservative random-effect meta-analysis. To explore sources of heterogeneity, subgroup analysis was performed according to different meditation forms (standard and nonstandard MBSR), training durations, headache types, and different control groups. Control groups such as pharmacotherapy, wait-list, and delayed treatment were combined to one comparator as these were all passive controls. In contrast, the relaxation and education groups were deemed as active controls. Publication bias was not assessed due to the limited number of studies. A value of P < 0.05 was considered as statistically significant. All statistical analyses were performed using Revman 5.3 (Cochrane Collaboration).
As shown in Figure 1, 448 articles were identified from five databases. Of these, 128 were duplicates. From the remainder, 286 articles were excluded through title screening, and 19 articles were excluded by abstract screening. After the review of 15 full-text articles, 11 studies met the eligibility criteria for this study.
The characteristics of the included studies are summarized in Table 1. Of the 11 eligible studies, four studies were conducted in the United States, three in Australia, three in Iran and one in India. In 10 studies, the mean age of patients ranged from 30 to 45 years; in one study, the mean age of patients was 19.1 years. The studied subtypes of headache included migraine (1 study), TTH (7 studies), and migraine mixed with TTH (three studies, of which one focused on migraine). Control groups included the usual pharmacotherapy (three studies), wait-list (five studies), delayed treatment (1 study), relaxation (one study), and education (one study) groups. The usual groups were on standard pharmacotherapy. The wait-list group as well as the delayed treatment group received the treatment after the active treatment group was treated. The relaxation group received progressive muscle relaxation. The educational group received education from a neurologist who specialized in headache and pain management. Interventional methods included standard MBSR, MBCT, brief mindfulness-based therapy, mindfulness meditation, and different meditations within subgroups, most of which were combined with additional homework [Table 1]. An interventional form of transcendental meditation was not found on literature search. Sample size was calculated only in five studies, of which four were adequately powered to detect an effect [Table 2]. The other six studies were feasibility or pilot studies.
Based on the clinical or psychosocial characteristics, the outcomes were divided into clinical and humanistic outcomes. The clinical outcomes reported in these studies were headache intensity (seven studies), headache frequency (five studies), headache duration (four studies), and pain tolerance (two studies). Humanistic outcomes measured in the studies included mindful awareness in four studies, perceived stress in three studies, quality of life in two studies, and self-efficacy in two studies [Supplementary Files 2-4].
Forest plots of meta-analysis data for pain tolerance (a) and perceived stress (b). Effect sizes overlapped with zero reflect no significant difference between mindfulness meditation and control groups. Summary statistics were computed via random effects meta-analysis.
Subgroup analysis of pain intensity according to different items: (a) different types of headaches, (b) different ages and (c) different control groups.
Study quality and risk of bias
The YQRS score of inclusive studies varied from 16 to 26 points. Seven out of the eleven publications were graded as being at low risk of bias (57–74%), and the remainders were ranked as being at high risk of bias (45% and 48.5%). Quality criteria that these studies did not meet included measurement bias (eight studies), treatment expectations (nine studies), follow-up (eight studies), intention-to-treat analysis (10 studies), and sufficient sample size (seven studies). The quality rating for each study is displayed in Table 2.
Heterogeneity was substantial for pain intensity (I2 = 88%, P < 0.000) [Figure 2a]. We found that heterogeneity was resolved (I2 = 0%, P = 0.69) [Figure 2b] when only studies that used standard MBSR meditation forms were included in the analysis. Moreover, we found that heterogeneity was resolved (I2 = 0%, P = 0.6) [Figure 2c] when the intervention duration lasted for 8 weeks. For self-efficacy, heterogeneity was moderate (I2 = 33%, P = 0.22) with a small sample size [Figure 3d].
Mindfulness meditation for pain intensity
The results of meta-analysis for outcomes reported by more than one study for the mindfulness group were compared with control group and are displayed in Figures 2, 3 and Supplementary Files 2, 3. Pain intensity was the reported outcome in seven studies. The combined pain intensity response was −0.89 (95% CI, −1.63 to −0.15; P = 0.02) with heterogeneity (I2 = 88%) [Figure 2a]. Further, we conducted a sensitivity analysis according to the quality of these studies. The combined pain intensity response from the five studies at low risk of bias was −0.49 (95% CI, −1.12–0.14; P = 0.13) with heterogeneity (I2 = 78%). Figure 2b and 2c, respectively, show subgroup analysis of pain intensity according to different meditation forms and different therapy durations. In the subgroup analysis of different meditation forms, MBSR intervention displayed a positive influence on pain intensity with SMD [−1.07, 95% CI, −1.46 to −0.66; P < 0.000; I2 = 0%; Figure 2b]. In the subgroup analysis of different therapy durations, the 8-week intervention showed a significant effect [P < 0.000, I2 = 0%; Figure 2c]. In the subgroup analysis of different types of headache, intervention for migraine had a positive effect (P = 0.01; I2 = 0%) with small sample size [Supplementary File 3a]. In the subgroup analysis of age, the intervention showed a positive influence on older participants [P = 0.01; I2 = 87%; Supplementary File 3b]. A subgroup analysis of different control groups revealed a significant effect with meditation as compared to passive controls (P = 0.01; I2 = 87%), but when compared to active controls a meaningful result was not achieved because only one study remained [Supplementary File 3c].
Mindfulness meditation for other indices
Meditation program reduced headache frequency [P = 0.02; I2 = 71%; Figure 3a], but had no significant effect on the duration [P = 0.1; I2 = 65%; Figure 3b]. Quality of life assessment was carried out for two studies, and the combined response was −0.37 [95% CI, −0.82–0.07; P = 0.1; I2 = 0%; Figure 3c]. There was a significant change in the combined effect size of self-efficacy [−1.15, 95% CI, −1.97 to −0.33; P = 0.006; I2 = 33%; Figure 3d].
Although the meta-analysis found limited evidence for the effectiveness of mindfulness-based interventions in treating primary headache, it revealed that mindfulness-based intervention might have a positive impact on headache intensity. However, a sensitivity analysis to the studies at low risk of bias may suggest a possible overestimation of pain intensity improvement in all studies. Based on the analysis of different subgroups, it was found that the heterogeneity of pain intensity might be derived from other meditation forms such as MBCT and brief MBSR and from other types of headache such as TTH. MBSR was developed by Kabat-Zinn and Hanh and MBCT was proposed by Segal et al., and both were developed as secular clinical interventions. MBCT does not require the adoption of any specific spiritual orientation or belief system. A further source for MBCT is cognitive-behavioral therapy (CBT) – a psychotherapy based on the assumption that the way we perceive events largely determines how we feel about them and, in turn, how we behave. This specific spiritual orientation or belief system of MBSR may help reduce pain intensity. After subgroup analysis of different types of headache, heterogeneity was resolved in the subgroup of migraine with a small sample size. However, regarding long-term effect with mindfulness meditation, more practice helps gain more in terms of benefits. In the future, we may conduct a study focusing on the difference between MBSR and MBCT.
The aim of CBT is to help patients learn how to think and behave in more adaptive ways. In the context of chronic pain, CBT components typically include cognitive restructuring of maladaptive pain-related beliefs, coping skills training, problem-solving training, and psychoeducation of pain and their particular syndromes. CBT often includes several behavioral strategies such as relaxation training, strategies for behavioral activation, pacing, activity scheduling, and motivating physical activity. Although CBT has become a first-line psychosocial treatment for individuals with chronic pain, mindfulness meditation has shown the same effect as CBT when treating adult patients with low back pain. Furthermore, mindfulness meditation could reduce the anxiety and stress levels as the biofeedback.
A subgroup analysis of passive and active groups showed meditation had a significant effect in the passive groups including usual medication, wait-list, and delayed treatment, as compared to the active group. A pooled-effect was derived from six passive controls and one active control. This is not paradoxical with regard to Davidson's conclusion, which suggested MBSR does not differ with the active control group (Health Enhancement Program; a structurally equivalent, active control condition). Although the pain rating was tested, all subjects were without headache in Davidson's research.
Mindfulness-based intervention may influence headache frequency, but there was no significant change in the duration of headache. Pain tolerance and perceived stress did not change. The intervention had a positive effect on self-efficacy within small sample sizes. The methodological quality of the included studies was variable. We could not conduct quantitative tests to detect potential publication bias because only seven studies were available for the primary outcome. We reviewed unpublished trials related to our study in the clinicaltrials.gov registration database and found two trials that appeared to have not been completed before November 2016. As only 2 outcomes were excluded from the analysis, the findings of our meta-analysis are less likely to be affected by publication bias.
In clinical application, mindfulness meditation may reduce the intensity and frequency of primary headache with no associated side effects. Moreover, it helps improve self-efficacy as proposed by Bandura. Self-efficacy is the extent or strength of one's belief in one's own ability to complete tasks and reach goals. When self-efficacy is elevated, patients may have a better quality of life. More humanistic outcomes should be measured as the process of pain essentially includes psychosocial information. As a complementary and alternative medicine, mindfulness-based intervention has higher cost-efficiency, is convenient to practice at home, and does not require any special facilities. Despite the limitations of this analysis, the evidence suggests that mindfulness meditation may help control headache. Thus, physicians should suggest to their patients that they learn mindfulness meditation in addition to standard medical care for headache.
As the review analyzed pooled effects from a small number of studies, this limited our ability to draw definitive conclusions. In addition, some studies had limitations as they were underpowered. Inclusion of studies that are analyzed by the person completing the program may result in bias in favor of treatment. Although some studies referred to the home practice of the meditation form, the extent of completion of the intervention at home was not assessed. Three studies did not specify therapist training which may have affected the quality of the intervention. Intention-to-treat analysis was performed only in one study. There were three problems in the included studies as follows: lack of blinding to outcome assessment, lack of allocation concealment, and lack of intention-to-treat analysis.
Almost all of the included studies measured pain intensity with the Likert scale, which is relatively subjective. Only two studies tested pain sensitivity in a cold-water task, which could be relatively objective. However, it was interesting that the cold-water task tested the cold sensitivity of the skin over the hand rather than that over the head, or the skin around the trigger point. Only a few studies investigated the effects of mindfulness meditation on headache during follow-up. However, for chronic headache, more attention should be paid to long-term training effect of mindfulness meditation practice.
In conclusion, based on a small number of studies that limited our ability to draw a definitive conclusion, mindfulness meditation may be a promising treatment option for the amelioration of primary headache. Headache intensity was reduced by mindfulness meditation in the form of MBSR and when compared with passive controls. The attenuation of headache intensity may be due to the reduction of headache frequency and improvement of self-efficacy. In the future research, headache sensitivity should be tested objectively. Further, larger sample size and high-quality experimental designs are required to conclusively determine the role of mindfulness meditation in headache.
Supplementary information is linked to the online version of the paper on the Chinese Medical Journal website.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
The authors extend their sincere thanks to Dr. Rui-Li Wei for his assistance with manuscript writing.
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Edited by: Yuan-Yuan Ji