The effects of mind-body therapies on the immune system: meta-analysis

Abstract

Importance: Psychological and health-restorative benefits of mind-body therapies have been investigated, but their impact on the immune system remain less defined.

Objective: To conduct the first comprehensive review of available controlled trial evidence to evaluate the effects of mind-body therapies on the immune system, focusing on markers of inflammation and anti-viral related immune responses.

Methods: Data sources included MEDLINE, CINAHL, SPORTDiscus, and PsycINFO through September 1, 2013. Randomized controlled trials published in English evaluating at least four weeks of Tai Chi, Qi Gong, meditation, or Yoga that reported immune outcome measures were selected. Studies were synthesized separately by inflammatory (n = 18), anti-viral related immunity (n = 7), and enumerative (n = 14) outcomes measures. We performed random-effects meta-analyses using standardized mean difference when appropriate.

Results: Thirty-four studies published in 39 articles (total 2, 219 participants) met inclusion criteria. For inflammatory measures, after 7 to 16 weeks of mind-body intervention, there was a moderate effect on reduction of C-reactive protein (effect size [ES], 0.58; 95% confidence interval [CI], 0.04 to 1.12), a small but not statistically significant reduction of interleukin-6 (ES, 0.35; 95% CI, -0.04 to 0.75), and negligible effect on tumor necrosis factor-α (ES, 0.21; 95% CI, -0.15 to 0.58). For anti-viral related immune and enumerative measures, there were negligible effects on CD4 counts (ES, 0.15; 95% CI, -0.04 to 0.34) and natural killer cell counts (ES, 0.12, 95% CI -0.21 to 0.45). Some evidence indicated mind-body therapies increase immune responses to vaccination.

Conclusions: Mind-body therapies reduce markers of inflammation and influence virus-specific immune responses to vaccination despite minimal evidence suggesting effects on resting anti-viral or enumerative measures. These immunomodulatory effects, albeit incomplete, warrant further methodologically rigorous studies to determine the clinical implications of these findings for inflammatory and infectious disease outcomes.

Figure 1. Literature Search and Study Selection. Legends:

CD4 = cluster of differentiation 4 protein; CRP = c-reactive protein; IL-6 = interleukin-6; INF-γ = Interferon-gamma; NK count = natural killer cell count; TNF-α = Tumor necrosis factor. ^aThe studies were conducted in 9 countries (United States, China, India, Australia, Spain, Germany, Iran, Norway, and the United Kingdom). ^bThe sum of study number exceeds the total number of studies included due to some studies reported multiple outcomes across categories.

Figure 2. Meta-analysis of RCTs comparing the effect of mind-body therapies with control interventions on inflammatory markers: CRP (panel a), IL-6 (panel b), and TNF-α (panel c). Legends:

CRP = c-reactive protein; IL-6 = interleukin 6; Med = meditation; QG = Qi Gong; TC = Tai Chi; TNF-α = Tumor necrosis factor; Tx = treatment; RA = rheumatoid arthritis; SMD = standardized mean difference. Risk of bias: L = low; M = medium; H = high (see Table S2 for details). Zautra 2008 reported only subgroup results (grp 1 = RA patients with depression; grp 2 = RA patients without depression) and data from each subgroup were entered in the meta-analysis separately. P-values adjacent to I-squared results are p-values for heterogeneity testing (P<0.05 indicates significant heterogeneity), and p-values adjacent to meta-analysis pooled results (diamonds) are p-values for the pooled effect sizes.

Figure 3. Subgroup meta-analysis of RCTs comparing the effect of mind-body therapies with control interventions on CRP and IL-6 by clinical populations (panels a and b), by MBT types (panels c and d), and by control types (panels e and f). Legends:

SMD = standardized mean difference. MBT = mind-body therapies. P-values adjacent to I-squared results are p-values for heterogeneity testing (P<0.05 indicates significant heterogeneity and “I-squared = n/a” indicates that there was only 1 study in the subgroup so heterogeneity was not applicable), and p-values adjacent to meta-analysis pooled results (diamonds) are p-values for the pooled effect sizes.

Figure 4. Meta-analysis of RCTs comparing the effect of mind-body therapies with control interventions on enumerative markers: CD4 count (panel a) and NK count (panel b). Legends:

CD4 = cluster of differentiation 4 protein; Med = meditation; NK count = natural killer cell count; Tx = treatment; SMD = standardized mean.