Gut microbiota and major depressive disorder: A systematic review and meta-analysis.

BACKGROUND: Growing attention has been paid to the field of gut microbiota for mental disorders over the last decade. However, to our knowledge, no studies have conducted systematic reviews on the association between gut microbiota and major depressive disorder (MDD) in both interventional and non-interventional studies. METHODS: We conducted a systematic review and meta-analysis of 16 studies (10 observational [701 participants] and six interventional trials [302 participants]) examining gut microbiota in patients with MDD. The primary outcome measures were differences in the profile of microbiota in the observational studies, and symptom changes for depression between pre- and post-intervention with probiotics in the interventional trials. RESULTS: In the observational studies, significant reductions in several taxa at the family and genus levels were observed in patients with MDD compared to non-depressed controls. In the interventional studies with probiotics, a significant improvement was found in depressive symptomatology compared to controls (SMD = -1.62, 95% CI = -2.73 to -0.51, p< 0.01). LIMITATIONS: Lack of consideration of the effects of diet and pharmacotherapy was a possible limitation. CONCLUSIONS: Our results indicate that several taxa at the family and genus levels, specifically family Prevotellaceae, genus Corprococcus, and Faecalibacterium, were decreased in MDD compared to non-depressed controls in observational studies, and depressive symptoms were improved compared to controls in interventional studies with probiotics. Due to the limited number of studies, further studies considering diet and pharmacotherapy are needed to explore the relationships between gut microbiota and MDD in humans.

Effects of mindfulness-based interventions on biomarkers in healthy and cancer populations: a systematic review.

BACKGROUND: Only a small number of articles have investigated the relationship between mindfulness-based interventions (MBIs) and biomarkers. The aim of this systematic review was to study the effect of MBIs on specific biomarkers (cytokines, neuropeptides and C-reactive protein (CRP)) in both healthy subjects and cancer patients. METHODS: A search was conducted using PubMed, EMBASE, PsycINFO and the Cochrane library between 1980 and September 2016. RESULTS: A total of 13 studies with 1110 participants were included. In the healthy population, MBIs had no effect on cytokines, but were found to increase the levels of the neuropeptide insulin-like growth factor 1 (IGF-1). With respect to neuropeptide Y, despite the absence of post-intervention differences, MBIs may enhance recovery from stress. With regard to CRP, MBIs could be effective in lower Body Mass Index (BMI) individuals. In cancer patients, MBIs seem to have some effect on cytokine levels, although it was not possible to determine which specific cytokines were affected. One possibility is that MBIs might aid recovery of the immune system, increasing the production of interleukin (IL)-4 and decreasing interferon gamma (IFN-γ). CONCLUSIONS: MBIs may be involved in changes from a depressive/carcinogenic profile to a more normalized one. However, given the complexity and different contexts of the immune system, and the fact that this investigation is still in its preliminary stage, additional randomized controlled trials are needed to further establish the impact of MBI programmes on biomarkers in both clinical and non-clinical populations.

Effects of Mindfulness-Based Interventions on Salivary Cortisol in Healthy Adults: A Meta-Analytical Review.

Objective: The aim of the present study was to elucidate the effects of Mindfulness-based interventions (MBIs) on salivary cortisol levels in healthy adult populations. Method: We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs), published between January 1980 and June 2015 in PubMed, EMBASE, PsycINFO and the Cochrane library. The PRISMA and Cochrane guidelines were followed. The pooled effect sizes were calculated with the random-effects model, using Hedges' g-values, and heterogeneity was measured using the I2 statistic. The contribution of different characteristics of participants and programmes were assessed by meta-regression models, using beta coefficients. Results: Five RCTs with 190 participants in total were included in this systematic review. The overall effect size (ES) for improving the state of health related to cortisol levels was moderately low (g = 0.41; p = 0.025), although moderate heterogeneity was found (I2 = 55; p = 0.063). There were no significant differences between active (g = 0.33; p = 0.202) and passive (g = 0.48; p = 0.279) controls, but significant differences were found when comparing standard (g = 0.81; p = 0.002) and raw (g = 0.03; p = 0.896) measures. The percentage of women in each study was not related to ES. Nevertheless, age (beta = -0.03; p = 0.039), the number of sessions (beta = 0.33; p = 0.007) and the total hours of the MBI (beta = 0.06; p = 0.005) were significantly related to ES, explaining heterogeneity (R2 = 1.00). Conclusions: Despite the scarce number of studies, our results suggest that MBIs might have some beneficial effect on cortisol secretion in healthy adult subjects. However, there is a need for further RCTs implemented in accordance with standard programmes and measurements of salivary cortisol under rigorous strategies in healthy adult populations.