Objective: To examine the relation between the consumption or avoidance of meat and psychological health and well-being. Methods: A systematic search of online databases (PubMed, PsycINFO, CINAHL Plus, Medline, and Cochrane Library) was conducted for primary research examining psychological health in meatconsumers and meat-abstainers. Inclusion criteria were the provision of a clear distinction between meat-consumers and meat-abstainers, and data on factors related to psychological health. Studies examining meat consumption as a continuous or multi-level variable were excluded. Summary data were compiled, and qualitative analyses of methodologic rigor were conducted. The main outcome was the disparity in the prevalence of depression, anxiety, and related conditions in meat-consumers versus meat-abstainers. Secondary outcomes included mood and self-harm behaviors. Results: Eighteen studies met the inclusion/exclusion criteria; representing 160,257 participants (85,843 females and 73,232 males) with 149,559 meat-consumers and 8584 meat-abstainers (11 to 96 years) from multiple geographic regions. Analysis of methodologic rigor revealed that the studies ranged from low to severe risk of bias with high to very low confidence in results. Eleven of the 18 studies demonstrated that meat-abstention was associated with poorer psychological health, four studies were equivocal, and three showed that meat-abstainers had better outcomes. The most rigorous studies demonstrated that the prevalence or risk of depression and/or anxiety were significantly greater in participants who avoided meat consumption. Conclusion: Studies examining the relation between the consumption or avoidance of meat and psychological health varied substantially in methodologic rigor, validity of interpretation, and confidence in results. The majority of studies, and especially the higher quality studies, showed that those who avoided meat consumption had significantly higher rates or risk of depression, anxiety, and/or self-harm behaviors. There was mixed evidence for temporal relations, but study designs and a lack of rigor precluded inferences of causal relations. Our study does not support meat avoidance as a strategy to benefit psychological health.

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We examined changes in brain rhythms in relation to optimal performance in self-paced sports. Eight studies met the inclusion/exclusion criteria, representing 153 participants and eight different sports. We found that (a) optimal performance is characterised by increased alpha (g = .62, p = .02) and theta (g = .74, p = .002) across the cortex; (b) during optimal performance the frontal lobe is more relaxed (higher alpha; g = 1.06, p = .18) and less busy (lower theta; g = .38, p = .08), in comparison to the other brain lobes; (c) for the same given task, experts' brains are more relaxed (higher alpha, g = .89, p = .34) and less busy (lower theta, g = .91, p = .54) than novices' brains. Theoretically, our findings suggest that neural efficiency, neural proficiency, and transient hypofrontality are likely complementary neural mechanisms that underpin optimal performance. In practice, neurofeedback training should teach athletes how to amplify and suppress their alpha and theta activity across the brain during all movement stages.

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in this meta-analysis, we examined the quantitative relation between meat consumption or avoidance, depression, and anxiety. in June 2020, we searched five online databases for primary studies examining differences in depression and anxiety between meat abstainers and meat consumers that offered a clear (dichotomous) distinction between these groups. Twenty studies met the selection criteria representing 171,802 participants with 157,778 meat consumers and 13,259 meat abstainers. we calculated the magnitude of the effect between meat consumers and meat abstainers with bias correction (Hedges's g effect size) where higher and positive scores reflect better outcomes for meat consumers. Meat consumption was associated with lower depression (Hedges's g = 0.216, 95% Ci [0.14 to 0.30], p < .001) and lower anxiety (g = 0.17, 95% Ci [0.03 to 0.31], p = .02) compared to meat abstention. Compared to vegans, meat consumers experienced both lower depression (g = 0.26, 95% Ci [0.01 to 0.51], p = .041) and anxiety (g = 0.15, 95% Ci [-0.40 to 0.69], p = .598). Sex did not modify these relations. Study quality explained 58% and 76% of between-studies heterogeneity in depression and anxiety, respectively. The analysis also showed that the more rigorous the study, the more positive and consistent the relation between meat consumption and better mental health. The current body of evidence precludes causal and temporal inferences.Many have unskillfully written upon the preservation of health; particularly by attributing too much to the choice, and too little to the quality of meats.