Yoga is one of the most widely used complementary and alternative medicine therapies to manage illness. This meta-analysis aimed to determine the effects of yoga on psychological health, quality of life, and physical health of patients with cancer. Studies were identified through a systematic search of seven electronic databases and were selected if they used a randomized controlled trial design to examine the effects of yoga in patients with cancer. The quality of each article was rated by two of the authors using the PEDro Scale. Ten articles were selected; their PEDro scores ranged from 4 to 7. The yoga groups compared to waitlist control groups or supportive therapy groups showed significantly greater improvements in psychological health: anxiety (
Cancer is a leading cause of death worldwide. The disease accounted for 7.4 million deaths (or around 13% of all deaths worldwide) in 2004 [
In addition to physical symptoms, people with cancer nearly always experience considerable levels of psychological distress. Psychological health in cancer patients is defined by the presence or absence of distress as well as the presence or absence of positive wellbeing and psychological growth. It is determined by the balance between two classes of factors: the stress and burden posed by the cancer experience and the resources available for coping with this stress and burden [
Many patients with cancer use forms of complementary and alternative medicine (CAM) to help manage the effects of their illness [
Yoga, as a main component of the Mindfulness-Based Stress Reduction (MBSR) program [
Some studies have specifically demonstrated potential psychological benefits of yoga in various clinical populations, including patients with depression [
The aim of this meta-analysis was to determine the effects of yoga on psychological health (i.e., anxiety, depression, distress, and stress), quality of life, and physical health of people with cancer. In contrast to previous reviews [
We searched Medline, PubMed, PEDro, EMBASE, the Cochrane Library, PsycINFO (formerly PsychLit), and CEPS (a Chinese database) from January 1970 to July 2010 using the keywords cancer, oncology, yoga, mindfulness, stress reduction, psychological health, physical health, quality of life, and randomized controlled trials (RCT) for relevant studies in English and Chinese. The reference sections of relevant articles were also reviewed by the authors.
Two reviewers (Lin and Hu) independently evaluated the abstracts identified by our search. To be included in the final analysis, studies had to use a randomized control trial design to examine the effects of yoga or MBSR on psychological health, quality of life, and physical health of cancer patients. Studies were excluded if they did not provide pre and poststudy data that were needed to calculate an effect size (standardized mean differences). If there were multiple assessment time points, the time point of postintervention was chosen. If data of change scores were not reported, attempts were made to obtain data from the study authors by e-mail. In cases in which change scores and standard deviations (SDs) were not obtainable, the study was excluded.
Two authors (Lin and Hu) independently assessed the methodological quality of the studies. PEDro Scale [
To evaluate the agreement of using the PEDro Scale, kappa statistic was calculated for measuring agreement between two authors. Values of kappa between 0.40 and 0.59 have been considered to reflect fair agreement, between 0.60 and 0.74 to reflect “good” agreement and 0.75 or more to reflect “excellent” agreement [
Changes from preintervention assessment to postintervention assessment were obtained directly from the study results or calculated by determining the difference between the reported mean before and after the intervention. Continuous outcomes were analyzed using weighted mean differences when all studies measured outcomes on the same scale. Standardized mean differences were used when all scales were assumed to measure the same underlying symptom or condition but some studies measured outcomes on different scales [
Heterogeneity was explored by Cochrane's
Sensitivity analysis was conducted to investigate potential sources of heterogeneity and to determine how sensitive the final conclusions of the study are to the particular method or study design feature that was used [
A total of 100 articles were identified after searching by keywords. Following the exclusion process, a total of 11 randomized controlled trials met the inclusion criteria. From these 11 abstracts, 10 were identified as appropriate for further examination and the full articles were collected. The excluded study evaluated natural killer cell counts, rather than physical health, psychological health, and quality of life as its outcome measure [
Flowchart detailing study selection.
The quality of the studies was assessed using the PEDro rating scale. Kappa statistics for agreement between reviewers on methodological quality was 0.80. The reviewers agreed on 90 of the 100 items (10 items for 10 studies) of the PEDro scale (90%). The intraclass correlation coefficients for interrater reliability of the total PEDro scores for individual raters were 0.94 (95% confidence interval (CI) 0.77~0.99). The median score for methodological quality of all included studies was 5 (PEDro scores ranged from 4 to 7). Of the 10 studies, 1 had a rating of 7 on a scale of 0–10 [
Methodological quality of analyzed studies.
PEDro criteria | Danhauer et al., 2009 [ | Raghavendra et al., 2009 [ | Rao et al., 2009 [ | Lengacher et al., 2009 [ | Banerjee et al., 2007 [ | Moadel et al., 2007 [ | Culos-reed et al., 2006 [ | Monti et al., 2006 [ | Cohen et al., 2004 [ | Speca et al., 2000 [ |
---|---|---|---|---|---|---|---|---|---|---|
(1) Eligibility criteria (not included in score) | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 |
(2) Random allocation | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 |
(3) Concealed allocation | 0 | 1 | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 0 |
(4) Baseline comparability | 1 | 1 | 1 | 1 | 0 | 1 | 0 | 0 | 1 | 1 |
(5) Blind subjects | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
(6) Blind therapists | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
(7) Blind assessors | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0 |
(8) Adequate followup | 0 | 1 | 0 | 1 | 1 | 0 | 1 | 0 | 1 | 0 |
(9) Intention-to-treat analysis | 1 | 0 | 1 | 1 | 0 | 1 | 0 | 1 | 0 | 1 |
(10) Between-group comparisons | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
(11) Point estimates and variability | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
Total | 5/10 | 6/10 | 6/10 | 7/10 | 6/10 | 5/10 | 4/10 | 4/10 | 4/10 | 5/10 |
Characteristic of included studies.
Author, year | No. of participants | Age, mean ± SD | Yoga type | Frequency | Duration, week | Outcome measures | Results |
---|---|---|---|---|---|---|---|
Danhauer et al., 2009 [ | 44 | 55.8 ± 9.9 | Restorative yoga: asanas (postures done with awareness), pranayama (voluntarily regulated nostril breathing), and savasana (deep relaxation) | 75 min weekly | 10 | QOL (SF-12 and FACT_B), fatigue (FACT-Fatigue), depression (CES-D), positive and negative affect (PANAS), and spirituality (FACIT-Sp), sleep quality (PSQI) | Group differences favoring yoga group in mental health, depression, positive affect, and spirituality. Significant baseline*group interactions in negative affect and emotional well-being. |
Raghavendra et al., 2009 [ | 88 | 46.0 ± 9.1 | Integrated yoga: asanas, pranayama, meditation, and yogic relaxation | 1 hr, 3 sessions weekly | 6 | Anxiety and depression (HADS), level of stress (PSS) | Significant between group differences on anxiety ( |
Rao et al., 2009 [ | 98 | NA | Integrated yoga: asanas, pranayama, meditation, and yogic relaxation | 60 min daily | 24 | Anxiety (STAI) | Overall decrease in both self-reported state anxiety ( |
Lengacher et al., 2009 [ | 84 | 57.5 ± 9.4 | MBSR: gentle yoga | 2 hr weekly | 6 | Fear of recurrence (Concerns about Recurrence Scale, anxiety (STAI), depressive symptoms (CES-D), optimism (Life Orientation Test), perceived stress (PSS), QOL (SF), social support (MOSS), spirituality | Significant between group differences on levels of depression, anxiety, fear of recurrence, energy, physical functioning, and physical role functioning (two-sided |
Banerjee et al., 2007 [ | 68 | 44.0 ± 1.4 | Integrated yoga: asanas, pranayama, nidra (guided relaxation with imagery) | 90 min weekly | 6 | Anxiety and depression (HADS), level of stress (PSS), DNA damage | Significant between group differences on HADS score, mean PSS, and DNA damage ( |
Moadel et al., 2007 [ | 128 | 54.8 ± 9.9 | Hatha yoga: physical stretches, breathing, and meditation | 1.5 hr weekly | 12 | QOL (FACT-G), spiritual well-being (FACIT-Sp), fatigue (FACIT-Fatigue), distress (Distressed Mood Index) | Significant between group differences on social well-being ( |
Culos-reed et al., 2006 [ | 38 | 51.1 ± 10.3 | Yoga: asanas, shevasana (relaxation) | 75 min | 7 | Anxiety and depression (POMS), QOL (EORTC QLQ-C30), symptom of stress (SOSI), physical activity (LSI), fitness (grip strength, flexibility, and Rockport Walking Test) | Significant differences between groups at post-intervention in global QOL, emotional function, diarrhea, and tension ( |
Monti et al., 2006 [ | 111 | 53.6 ± 11.5 | MBAT: gentle yoga | 2.5 hr weekly | 8 | Psychological distress and stress-related somatic complaints (SCL-90-R), Health-related QOL (SF-36) | Significant between group differences on symptoms of distress ( |
Cohen et al., 2004 [ | 39 | 51 | Tibetan yoga: controlled breathing, mindfulness, postures from Tsa lung (channels and vital breath), Trul khor (magical wheel) | weekly | 7 | Distress (IES), anxiety (STATE), depression (CES-D), fatigue (BFI), sleep disturbances (PSQI) | Significant between group differences on sleep disturbance scores ( |
Speca et al., 2000 [ | 90 | 51 | MBSR: gentle yoga | 90 min weekly | 7 | Anxiety and depression (POMS), stress-related symptoms (SOSI) | Significant between group differences on total mood disturbance, subscales of depression, anxiety, anger, confusion, vigor, and symptoms of stress. |
Abbreviations: QOL: quality of life; HADS: Hospital Anxiety and Depression Scale; PSS: Perceived Stress Scale; STAI: state trait anxiety inventory; SF-12: The 12-Item Short Form Health Survey; FACT-B: Functional Assessment of Cancer Therapy-Breast; FACT-Fatigue: Functional Assessment of Cancer Therapy-Fatigue; FACIT-Sp: Functional Assessment of Chronic Illness Therapy-Spirituality; CES-D: Center for Epidemiologic Studies Depression Scale; PSQI: Pittsburgh sleep quality inventory; PANSA: positive and negative affect schedule; FACT-G: The Functional Assessment of Cancer Therapy-General; FACIT-Fatigue: Functional Assessment of Chronic Illness Therapy-Fatigue; POMS: profile of mood states; SOSI: symptoms of stress inventory; EORTC QLQ-C30: European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Version 3.0; LSI: The Leisure Score Index; IES: Impact of Events Scale; STATE: Speilberger State Anxiety Inventory; BFI: Brief Fatigue Inventory; NA: not available; MBSR: mindfulness-based stress reduction; SF: Medical Outcomes Studies Short-Form General Health Survey; MOSS: Medical Outcomes Social Support Survey; MBAT: mindfulness-based art therapy; SCL-90-R: Symptoms Checklist Revised; SF-36: Medical Outcomes Study Short-Form Health Survey; CT: chemotherapy; min: minute; hr: hour.
The mean age of the participants across all the studies ranged from 43 to 58 years; 96% of participants were female and 4% male. The mean time since diagnosis ranged from 12 to 56 months. Studies included patients diagnosed with a variety of cancers, with 80% of participants having a breast cancer diagnosis and 63% of participants in early stage (Stages 0–II).
For seven studies [
The style of yoga used and the duration and frequency of the yoga sessions varied among all studies. Integrated yoga consisted of a set of asanas (postures done with awareness), breathing techniques, including pranayama (voluntarily regulated nostril breathing), and meditation and yogic relaxation techniques with imagery were used by 3 of the studies [
Comparison 1: yoga and control, psychological health, outcome: (a) Anxiety. (b) Depression. (c) Distress. (d) Stress.
Eight of the 10 studies used anxiety as an outcome measure, but there was little consistency among studies with respect to which test was used to evaluate anxiety [
Eight studies had at least one outcome measure for depression [
Two of the 10 studies included distress as an outcome measure [
Although Cohen et al. also included distress as one of their outcome measures, they used the Impact of Events Scale (IES) [
Several studies had outcome measures for the symptoms of stress [
Comparison 2: yoga and control, outcome: Quality of life.
Three of the 10 studies measured QOL [
Comparison 3: yoga and control, outcome, physical health, outcome: (a) Physical health. (b) Fatigue.
The outcome measures used to assess physical health in the cancer populations were SF-12 health survey physical component summary (PCS) [
Four of the 10 studies included fatigue as an outcome measure [
Only one study included fitness testing as one of its outcome measures; thus, this outcome was not included in the meta-analysis [
When we restricted the analysis to 8 studies [
Previous reviews have reported that yoga is beneficial for people with cancer in managing symptoms such as fatigue, insomnia, mood disturbances and stress, and improving quality of life [
Many cancer patients experience cancer-related psychological symptoms, including mood disturbances, stress, and distress [
However, the present findings do not address whether the psychological health benefits were attributable directly to yoga as a whole or the specific components of yoga, such as meditation and attention, in patients with cancer. Given that several yoga programs included meditation and relaxation with imagery, the positive results on psychological health might be obtained from these. Nevertheless, because of the nature of yoga interventions, it is impossible to control for placebo effects in investigations.
Although most RCTs reported anxiety, depression, and stress as outcome measures, the assessment tools used to measure their outcomes were inconsistent, which limits the generalization of the pooled results. Future research should focus on higher-quality trials with larger sample size in order to provide more precise estimates of the effects of yoga as a treatment.
Three of 10 RCTs reported quality of life outcomes, and the results showed a borderline difference between two groups. In contrast to the results of previous studies [
Our results showed that the overall effects for physical health outcomes were statistically nonsignificant. According to the previous review [
Moreover, our results did not show positive effects of yoga on fatigue. According to Sood’s review [
All studies included in the meta-analysis investigated participants with a diagnosis of cancer; however, the types of cancer varied among studies. Of the 10 included studies, 7 investigated breast cancer, 2 recruited mixed cancer populations, and 1 included patients with lymphoma. The result of Cohen’s study on lymphoma [
In addition, various factors are associated with the execution of the intervention such as yoga styles and treatment doses that may influence effect size. Four different styles of yoga were used among the included studies: restorative, integrated, hatha, and Tibetan. Treatment dose, including duration and frequency, and the adherence to yoga intervention and home practice may also affect treatment outcome. According to Carson’s study on yoga for women with metastatic breast cancer [
All studies had inevitable limitations such as that it was not possible to blind subjects or therapists from group allocations in this type of empirical study. Therefore, the highest possible score that each study could get would be 8 out of 10 when using a PEDro scale or other types of quality criteria.
Considerable heterogeneity existed (
The sensitivity analysis suggested that the effect of yoga was consistent across the intervention format and the types of cancer patients. As the literature search in this study was restricted to articles published in Chinese and English, this may introduce publication and language bias. Furthermore, this meta-analysis is limited due to the possibility of missing eligible unpublished or non-English studies and the fairly homogeneous studies included in the analysis. However, given the small number of studies included, the assessment of the heterogeneity or publication bias was difficult in this exposure.
In summary, our findings show potential benefits of yoga for people with cancer in improvements of psychological health. Because of the small number of studies having been conducted and the methodological limitations, the results should be regarded as preliminary and treated with caution.
Our preliminary findings also provide practitioners with important information that yoga may be a possible adjunctive therapy for cancer patients to help manage psychological distress and to improve quality of life. Nevertheless, more attention must be paid to the physical effects of yoga and the methodological quality of future research, as well as to improve these areas in the future.