The influence of diet quality on depression among adults and elderly: A population-based study

Background: Depression is the most common mental illness, achieving more than 264 million people worldwide. Although diet quality may be associated with depression symptoms, this relationship has not been deeply investigated among Brazilians. Therefore, this study was conducted to evaluate this relationship. Methods: This is a population-based cross-sectional study with representative individuals aged 18 years or over living in an urban area. Individuals were selected using a multistage sampling procedure. The Patient Health Questionnaire-9 was used to screen for major depressive episodes, and a Food Frequency Questionnaire was used to evaluate diet. We used a hierarchical model to conduct the analyses and calculated prevalence ratio using Poisson regression. Results: A total of 820 subjects were assessed, with mean age of 54.8 (+/- 17.4) years. Prevalence of major depressive episodes was 29.2%. After final adjustment, diet quality remained directly associated with depression (p = 0.024). Individuals with the worst diet quality were 39% more likely to have major depressive episodes when compared to those who had the best diet quality. Depression was also associated with consumption of soda or artificial juice and are food markers of unhealthy diets. Limitations: The cross-sectional design does not establish whether the associations are causal, and the Patient Health Questionnaire-9 is a screening scale - not a diagnostic tool; however, it is easy, quick to apply, and is widely used in epidemiological studies. Conclusion: The results provide important evidence about the role of diets on that mood disorder, which contributes to management approaches to depression.