The state of mind of vegetarians: Psychological well-being or distress?

Meat consumption & positive mental health: A scoping review

The objective of this scoping review was to examine the breadth of the existing literature on the relation between meat consumption or meat abstention and positive psychological functioning. In April 2022, we conducted a systematic search of online databases (PubMed, PsycINFO, CINAHL Plus, Medline, Cochrane Library, and Web of Science) for primary research examining positive psychological functioning in meat consumers and those who abstain from meat. Thirteen studies met the inclusion/exclusion criteria, representing 89,138 participants (54,413 females and 33,863 males) with 78,562 meat consumers and 10,148 meat abstainers (13-102 years) from multiple geographic regions. The primary outcomes were life satisfaction, "positive mental health", self-esteem, and vigor. The secondary outcomes were "meaning in life", optimism, positive emotions, and psychological well-being. Eight of the 13 studies demonstrated no differences between the groups on positive psychological functioning, three studies showed mixed results, and two studies showed that compared to meat abstainers, meat consumers had greater self-esteem, "positive mental health", and "meaning in life". Studies varied substantially in methods and outcomes. Although a small minority of studies showed that meat consumers had more positive psychological functioning, no studies suggested that meat abstainers did. There was mixed evidence for temporal relations, but study designs precluded causal inferences. Our review demonstrates the need for future research given the equivocal nature of the extant literature on the relation between meat consumption and meat abstention and positive psychological functioning.

Life of a vegetarian college student: Health, lifestyle, and environmental perceptions

Objective To examine health behavior and environmental perception differences among vegetarian and nonvegetarian students. Participants: First-year university students (n = 1078) from eight United States universities. Methods: Data were obtained from base 2015 and followup 2016 assessments. Vegetarians and nonvegetarians were compared for anthropometrics, lifestyle behaviors, and campus environmental perceptions (CEPS). Results: Vegetarians had smaller waist circumference, lower systolic blood pressure, higher fruit and vegetable consumption, lower percentage of energy obtained from fat, and higher perceived stress. Vegetarians expressed a lower rating of perceptions of health policies on campus. Conclusion: A clear difference in indicators of physical health does not appear, however, vegetarian students show positive dietary patterns which can promote positive health outcomes. Further, vegetarians had lower perceptions of health policies on campus. Results can be used by administrators to ensure policies are in place to support health of students as currently vegetarian students see limitations in the environmental health policies.

Vegetarian diet and depression scores: A meta-analysis

BACKGROUND

Several studies have suggested an association between vegetarian diet and higher depression scores. However, some studies have also shown an effect in the opposite direction, indicating lower depression scores in vegetarians. Given this discrepancy in the literature, this meta-analysis was aimed to determine whether there is a significant association between vegetarian diet and depression scores across different published studies.

METHODS

A keyword search in major databases was conducted. Studies reporting depression scores in vegetarians and a non-vegetarian control group were included. Meta-analysis following a conditional random-effects procedure was conducted in R.

RESULTS

After duplicates were removed and studies were analyzed for inclusion criteria, k=13 studies with an overall n of 49889 participants (8057 vegetarians and 41832 non-vegetarian controls) were included in the analysis. Random-effects meta-analysis revealed a significant difference between vegetarians and non-vegetarians, with vegetarians showing higher depression scores than non-vegetarians.

LIMITATIONS

The heterogeneity between studies was high and geographical variation in study location was low, limiting cross-cultural insights.

CONCLUSIONS

Vegetarians show higher depression scores than non-vegetarians. However, due to high heterogeneity of published studies, more empirical research is needed before any final conclusions can be drawn. Also, empirical studies from a higher number of different countries would be desirable.

Meat and mental health: A meta-analysis of meat consumption, depression, and anxiety

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.

Adherence to the vegetarian diet may increase the risk of depression: a systematic review and meta-analysis of observational studies

CONTEXT

Several epidemiological studies have investigated the association between a vegetarian diet and risk of depression, but because of inconsistency between studies, the exact association remains unclear.

OBJECTIVE

In this systematic review and meta-analysis, the relationship between vegetarian diets and risk of depression in observational studies was evaluated.

DATA SOURCES

The Medline, Embase, Scopus, ISI Web of Science, and Cochrane Library databases were searched from inception through September 1, 2020.

STUDY SELECTION

Observational studies were included that examined mean levels of depression and risk for depression in vegetarians compared with nonvegetarians.

DATA EXTRACTION

Pooled effect sizes were estimated using the random-effects model and were reported as standardized mean differences or odds ratios (ORs) with their corresponding 95%CIs. Heterogeneity was tested using the I2 statistic.

RESULTS

Combining 9 effect sizes in this meta-analysis illustrated that adherence to a vegetarian diet was associated with a 53% greater risk of depression compared with that of omnivores (95%CI, 1.14-2.07; I2 = 69.1%). Subgroup analysis of depression risk suggested that results depended on the type of vegetarian diet and country where the study was conducted. For studies that assessed a semivegetarian diet (OR, 1.86; 95%CI, 1.42-2.44; I2 = 35.7%) and those conducted in Europe and the United States (OR, 1.45; 95%CI, 1.06-1.98; I2 = 73.2%), there was a positive association between a vegetarian diet and depression, but in lacto-ovo vegetarians and Asian countries, a null association was found. Comparing mean depression scores showed no evidence of difference between vegetarians and nonvegetarians (n = 16; standardized mean difference, 0.10; 95%CI, -0.01 to 0.21; I2 = 79.1%).

CONCLUSION

Vegetarian diet significantly increased depression risk; however, the findings were not robust, and more studies are required to investigate the vegetarian diet and depression association.

Vegetarianism and veganism compared with mental health and cognitive outcomes: a systematic review and meta-analysis

CONTEXT

Vegetarian and vegan diets are increasing in popularity. Although they provide beneficial health effects, they may also lead to nutritional deficiencies. Cognitive impairment and mental health disorders have a high economic burden.

OBJECTIVE

A meta-analysis was conducted to examine the relationship between vegan or vegetarian diets and cognitive and mental health.

DATA SOURCES

PubMed, Scopus, ScienceDirect, and Proquest databases were examined from inception to July 2018.

STUDY SELECTION

Original observational or interventional human studies of vegan/vegetarian diets were selected independently by 2 authors.

DATA EXTRACTION

Raw means and standard deviations were used as continuous outcomes, while numbers of events were used as categorical outcomes.

RESULTS

Of 1249 publications identified, 13 were included, with 17 809 individuals in total. No significant association was found between diet and the continuous depression score, stress, well-being, or cognitive impairment. Vegans/vegetarians were at increased risk for depression (odds ratio = 2.142; 95%CI, 1.105-4.148) and had lower anxiety scores (mean difference = -0.847; 95%CI, -1.677 to -0.018). Heterogeneity was large, and thus subgroup analyses showed numerous differences.

CONCLUSIONS

Vegan or vegetarian diets were related to a higher risk of depression and lower anxiety scores, but no differences for other outcomes were found. Subgroup analyses of anxiety showed a higher risk of anxiety, mainly in participants under 26 years of age and in studies with a higher quality. More studies with better overall quality are needed to make clear positive or negative associations.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42018097204.

Meat and mental health: a systematic review of meat abstention and depression, anxiety, and related phenomena

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 meat-consumers 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.