Association between nonalcoholic fatty liver disease and depression: A systematic review and meta-analysis of observational studies

Background: Nonalcoholic fatty liver disease (NAFLD) is associated with an increased prevalence of psychological conditions such as depression and anxiety. However, the correlation between NAFLD and depression has not been well illustrated. Methods: Studies that investigate the association between nonalcoholic fatty liver disease and depression were searched in multiple electronic databases. Pooled odds ratios (ORs) and confidence intervals (CIs) of the included articles were calculated using a fixed- or random effects model. Results: A total of seven articles were included in this study. The results of the meta-analysis showed that compared with those without nonalcoholic fatty liver disease, individuals with it had a significantly increased risk of depression (pooled OR = 1.13, 95% CI: 1.03, 1.24, p = 0.007), and there was evidence that heterogeneity was not significant (I-2 = 13.6%, p for heterogeneity = 0.324). Moreover, depressed patients had a significantly increased risk of developing nonalcoholic fatty liver disease compared with non-depressed patients (pooled OR = 1.46, 95% CI: 1.15, 1.85, p = 0.002), and evidence of non-significant heterogeneity was observed (I-2 = 0%, p = 0.837 for heterogeneity). Limitations: The majority of the included articles in this study are cross-sectional studies and could not elucidate the causal relationship, so further longitudinal studies are needed to clarify the causal relationship. Conclusion: Nonalcoholic fatty liver and depression are highly correlated, the two interact with each other and have a high risk of comorbidities. In the future more high quality prospective studies will be needed to validate our results.